Unit Compilation II
Chapter 17
Cell
Reproduction and Differentiation
Table of Contents:
17.1 The cell cycle creates new cells
17.2 Replication, transcription, and translation: An
overview
a. Replication:
Copying DNA before cell division
b. Mutations are alterations in DNA
c. Mechanisms of DNA repair
d. Transcription: Converting a
gene’s code into mRNA
e. Translation: Making a protein
from RNA
17.3 Cell reproduction: One cell becomes two
a. Mitosis:
Daughter cells are identical to the parent cell
b. Cytokinesis divides one cell into
two identical cells
c. Mitosis produces diploid cells,
and meiosis produces haploid cells
d. Meiosis: Preparing for sexual
reproduction
e. Sex differences in meiosis: Four
sperm versus one egg
17.4 How cell reproduction is regulated
17.5 Environmental factors influence cell differentiation
a. Differentiation
during early development
b. Differentiation later in
development
17.6 Cloning an organism requires an
undifferentiated cell
a. Embryo
splitting: producing identical offspring
b. Somatic Cell Nuclear Transfer:
Cloning an Adult
17.7 Therapeutic cloning: Creating tissues and
organs
17.1 The cell cycle creates new cells
Cell cycle
New cells are created
from existing cells.
There are 2
periods of a cell cycle.
1)
Interphase- Johnson 2012
states that interphase is the beginning phase (long growth period). During this
phase, the cell grows and the DNA is duplicated in preparation for the next
division.
Interphase
has 3 subphases:
a)
G1
phase
·
Beginning
of cell cycle
·
Cell
is most active
b)
S
phase
·
DNA
synthesis occurs
c)
G2
phase
·
The
cell growth is slow
·
Prepares
for cell division
2)
Mitotic Phase- This is where
the nucleus and cytoplasm divide.
This
phase has 2 sub phases
a)
Mitosis
·
DNA
divides into two sets
·
Nucleus
divides
b)
Cytokinesis-
·
Cytoplasm
divides
·
Two new cells called “daughter” cells form
G0
·
Cells
stop growing
·
Stop
dividing
Sometimes
cells in tissues can be called back to start dividing again.
17.2
Replication, transcription, and translation: An overview
Replication
·
exact
copy of DNA
·
Occurs prior to every cell division
Transcription
·
Converts
portion of double-stranded DNA to single-strand mRNA.
·
Occurs
within the nucleus
Translation
·
Converts
a messenger RNA (mRNA) code into one or more proteins
·
Occurs in the cytoplasm
The
process of replication occurs when the DNA strand uncoils or unzips.
During the G1
phase (sub phase of Interphase), DNA molecule exist as long thin
Chromosomes. During the S phase, the
two strands of DNA unwind and replicate. This occurs at multiple sites along
the chromosome.
After
replication the duplicated chromosome, consist of sister chromatids, held
together by a centromere.
During
mitosis, the sister chromatids, condense and become visible.
Then
they are pulled apart, with one going to each daughter cell.
When
mitosis is complete, the single chromosome again takes on the more dispersed
form and is no longer visible.
17.2 b.
Mutations are alterations in DNA
Mutations
·
mistakes
made during DNA replication
·
for example, chemicals introduced to the fetus
like house hold cleaners
·
Physical forces
Mutations
occur most frequently during the DNA replication process.
Repair
enzymes can repair some mutations.
17.2 c.
Transcription: Converting a gene’s code into mRNA
Transcription
occurs in the nucleus. A portion of the double-stranded DNA molecule unwinds
temporarily and RNA polymerase assist in copying base sequences in RNA
nucleotide.
The
RNA molecule produced from the primary transcript (strand of RNA released from
the DNA) called the mRNA can be translated into amino acids that synthesizes
proteins.
The
primary transcript includes introns, which are edited out, and exons (carry
genetic information) are spliced appropriately.
A
messenger RNA strand is produced.
17.2 d. Translation: Making protein from RNA
http://www.vcbio.science.ru.nl/en/virtuallessons/cellcycle/trans/
accessed March 10, 2012
Genes from DNA
produce three different kinds of RNA
1) (mRNA) Messenger RNA: carries the
recipe for a new protein.
2) (tRNA) Transfer RNA- carries the code
for one amino acid. tRNA is folded into a particular shape.
3) (rRNA) Ribosomal RNA- Connects amino
acids together.
Translation
·
takes place in the cytoplasm
·
occurs in 3 stages
·
Assembly takes place on a ribosome.
1)
Initiation:
A tRNA carrying the “start” (AUG Codon) anticodon (A base triplet pairs to a
codon of mRNA) binds to the smaller ribosomal subunit and to the “start” codon
of the mRNA.
2)
Elongation:
tRNA molecules capture free amino acids and bring them to the appropriate codon
on the mRNA.
3)
Termination:
When a stop codon is reached the ribosomal subunits, and the newly formed
protein detach from the mRNA.
17.3 Cell
reproduction: One cell becomes two
2 Types of cell
reproduction processes:
1)
Mitotic
Cell Cycle: generates new diploid cells. Diploid cells contain chromosomes
in pairs.
2)
Meiotic
Cell Cycle: generates haploid gametes. Haploid cells contain chromosomes
not in pairs.
17.3a Mitosis: Daughter cells are identical to the
parent cell.
Mitotic Phase of
the cell cycle
·
nucleus
divides called mitosis
·
Cytoplasm
divides called the cytokinesis
Complete cell
cycle 18-24 hours. The cell spends most of its time in Interphase.
Mitosis and
Cytokinesis takes less than one hour of the complete cell cycle.
Mitosis ensures
that all cells of a complex organism have the same set of DNA.
Mitosis includes
a sequence of phases:
1)
Prophase
2)
Metaphase
3)
Anaphase
4)
Telophase
Prophase (Oellers Online Presentation 2012)
http://iknow.net/cell_div_education.html accessed March 10, 2012
·
Mitotic
spindle attaches to chromosomes to move them
·
Centrioles
migrate to cell poles. Centrioles are protein structures that dictate the place
of division.
·
Chromatin
condenses into visible chromosomes. Chromatins are threadlike form of DNA after
duplicated.
·
Nuclear
membrane dissolves.
·
Metabolic
activity decreases and cell is not making proteins at this point.
·
Duplicated
chromosomes form single line at the equator between centriole poles.
Anaphase (Oellers Online Presentation 2012)
·
Duplicated
DNA molecules separate and move toward opposite sides of the cell.
·
Cytokinesis
(division of cytoplasm) begins at this time.
·
Reverse
of prophase.
·
Mitotic
spindle disintegrates.
·
Nuclear
membrane reforms and chromosomes uncoil and revert to chromatin.
17.3b. Cytokinesis divides one cell into two
identical cells
Cytokinesis is
where the cell divides to produce two daughter cells.
Oellers 2012
states from her online presentation that a contractile ring of filaments form
at the midsection of the cell, tightens, forming a cleavage furrow. This
separates the cell and two daughter cells are formed.
The two daughter
cells are identical. They are called diploid cells.
17.3c. Mitosis produces diploid cells, and meiosis
produces haploid cells
Mitosis is used
for growth and repairs in body cells and is identical to parent.
All cells in the
human body divide by mitosis with the exception of the cells that form the
sperm and eggs.
Johnson 2012
states in his book Human Biology,
that all human cells have 46 chromosomes called diploid cells that reproduce by
first replicating the 46 chromosomes and then undergoing mitosis. The result is
two daughter cells that end up with 46 chromosomes that are identical to those
of the parent cell.
In diploid cells
one of each pair of chromosomes came from each parent, 22 pairs of autosomes
(homologous chromosomes) and the sex chromosome X and Y. Autosomes look
identical under the microscope and they have copies of the same genes in the
same location.
Gametes (sperm
and egg) are haploid cells they only have 23 chromosomes. Haploid cells are
created by meiosis a special cell division and process that occurs in ovaries
and testes.
17.3d. Meiosis: Preparing for sexual reproduction
Meiosis consists
of two nuclear divisions, which results in chromosomes being reduced by ½
during the form of the gametes and this causes daughter cells to become haploid
cells.
Meiotic Cell
Division consists of 2 Phases:
1)
Meiosis
I
2)
Meiosis
II
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmeiosis.html accessed 10
March 2012
Meiosis I:
Prophase I: The duplicated homologus chromosomes
pair up and swap segments in synapses (crossing over)
Metaphase I: Homologous pairs of chromosomes line
up.
Double line of
chromosomes pair.
Anaphase I
Pairs of
chromosomes separate, but duplicated chromosomes stay intact.
Telophase I and cytokinesis
End of meiosis
I: There are two haploid daughter cells, but chromosomes are still in
duplicated state.
Meiosis II
Prophase II
Metaphase II
Anaphase II
The duplicated chromatids separate
Telophase II and cytokinesis
The nuclei have the haploid
chromosome number (23 chromosomes)
Each of the two daughter
cells from meiosis I go through meiosis II. Meiosis II is like mitosis I except
that the chromosomes are not duplicated again and there are four haploid
daughter cells. During meiosis II the 23 chromosomes line up and the sister,
chromatids are separated from each other. Because of crossing over in Meiosis I,
the four haploid daughter cells are all different from one another.
17.3e. Sex differences in meiosis: Four sperm versus
one egg
Male
·
Four
sperm product from each cell enters meiosis, all sperm come out different from
one another.
·
All
viable functional
Female
·
Unequal
cytokinesis during meiosis I/II.
·
The
egg has a lot of cytoplasm around it for a better survival rate.
One-egg three
polar bodies produced from each cell entering meiosis. The polar body is produced
during meiosis I and can or may not divide again during meiosis II.
Meiosis II is
not complete until a sperm penetrates the egg.
17.4 How cell reproduction is regulated
Not all cells
divide at the same rate, for example, liver cells do not divide in adult hood.
An internal
cyclic control mechanism regulates the cell cycle.
The cycle can be
stopped at certain checkpoints by internal surveillance systems and is
influenced by conditions outside the cell.
17.5 Environmental factors influence cell differentiation
All cells have
the exact same set of DNA. They become different because of differentiation.
Differentiation is a cell that becomes different
from its parent or sister cell. They begin to express different genes due to
environmental influences.
17.6 Cloning an organism requires an
undifferentiated cell
Reproductive
cloning is making copies of the entire organism.
Requires
undifferentiated cells for the starting point
1)
Embryo Splitting
2)
Somatic Cell
Nuclear Transfer
17.6a. Embryo Splitting: producing identical
offspring
In embryo splitting,
an egg is fertilized in vitro and allowed to divide to the eight-cell stage. At
this stage, the cells are all still identical because they have not yet begun
to differentiate.
The cells are
then separated and each is implanted into a different surrogate mother.
Although the
offspring produced by embryo splitting are clones of each other, they are not
identical to either parent because they received some of their genes from each
parent.
17.6b. Somatic Cell Nuclear Transfer: Cloning an
Adult
Somatic cell
nuclear transfer can use any cell in the body except gametes.
This involves
combining a somatic cell (any cell in the body except gametes) from an adult
with an enucleated fertilized egg with its nucleus removed.
The nucleus is
removed from an unfertilized egg
A body cell from
the adult animal to be cloned is inserted into the egg
Electrical
current is applied to fuse the cells
The nucleus of
the animal to be cloned is now the nucleus of the egg
The egg is
implanted into a surrogate mother
The surrogate
mother gives birth to a clone.
Ex. Dolly the
first cloned sheep.
17.7 Therapeutic cloning: Creating tissues and
organs
Therapeutic
cloning is the cloning of human cells for treating patients.
The process for
therapeutic cloning takes the undifferentiated cells from human embryos and
clones them for use in patients with specific diseases for example Parkinson’s
disease.
A new gene therapy method
developed by University of Florida researchers has the potential to treat a
common form of blindness that strikes both youngsters and adults. The technique
works by replacing a malfunctioning gene in the eye with a normal working copy
that supplies a protein necessary for light-sensitive cells in the eye to
function.(Science News 2012).
References
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch. 17 Cell Reproduction and Differentiation. Retrieved March 10,
2012, from http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
Science News (2012). Researchers
Develop Gene Therapy That Could Correct a Common Form of Blindness. Retrieved
March 10, 2012 from http://www.sciencedaily.com/releases/2012/01/120123163412.htm
Chapter 18
Cancer:
Uncontrolled Cell Division and Differentiation
Table of Contents:
18.1 Tumors can be benign or cancerous
18.2 Cancerous cells lose control of their functions
and structures
18.3 How cancer develops
a. Mutant forms of proto-oncogenes,
tumor suppressor genes, and mutator genes contribute to cancer.
b. A variety of factors can lead to
cancer
c. The immune system plays an
important role in cancer prevention
18.4 Advances in diagnosis enable early detection
a. Tumor imaging: X-rays, PET and
MRI
b. Genetic testing can identify
mutated genes
c. Enzyme tests may detect cancer
markers
18.5 Cancer Treatments
a. Conventional cancer treatments:
Surgery, radiation, and chemotherapy
b. Magnetism and photodynamic
therapy target malignant cells
c. Immunotherapy promotes immune
response
d. “Starving” cancer by inhibiting angiogenesis
e. Molecular treatments target
defective genes
18.6 The 10 most common cancers
a. Skin cancer: Look for changes in
your skin
b. Lung cancer: Smoking is leading
risk factor
c. Breast cancer: Early detection
pays off
d. Prostate cancer: Most common
after age 50
e. Cancers of colon and rectum:
Tests can detect them early
f. Lymphoma: Cancers of lymphoid
tissues
g. Urinary bladder cancer: Surgery
is often successful if done early
h. Kidney cancer: Detected during
examination for a renal-related problem
i. Cancer of the uterus: Unusual
uterine bleeding is major symptom
j. Leukemia: Chemotherapy is often
effective
18.7 Most cancers can be prevented
18.1 Tumors can be benign or cancerous
Cancer- Johnson 2012 in “Human Biology” states
that cancer is a disease of cell division and differentiation. As cancer, cells
divide out of control and even invade other tissues, which may prevent the
proper functioning of organs and organ systems.
2 Key
Characteristics of normal cells
1)
Regulatory
Mechanisms (control rate of cell division)
2)
Remain
in one location.
Normal cells do
increase their rate of cell division as part of their normal function.
Hyperplasia refers to a substantial increase in the
rate of cell division.
Tumors
·
Increase
cell division (Hyperplasis)
·
Mass
or tumor (discrete mass of cells)
·
Cancerous
·
Benign
Benign Tumors
·
Non
cancerous
·
Remain
in 1 location
·
Well-defined
mass
Ex A mole is a
form of benign tumor (Johnson 2012)
18.2 Cancerous cells lose control of their functions
and structures
Picture on the left is a liver with cancerous cells.
Picture on the right are healthy liver cells
http://www.mayoclinic.com/health/medical/IM02827 Accessed 10 March 2012
Cancerous Cells
·
Cells
dividing rapidly
·
Nucleus
becomes larger
·
Less
cytoplasm
·
Cells
lose specialized functions and strucrtures (Dysplasia)
Dysplasia is an abnormal structural chance
considered a precancerous state. (Johnson 2012)
Cancerous Tumors
·
Abnormal
structure
·
Loss
of regulation of cell growth
·
In
situ cancer (tumor remains in one place)
Mestasis is the spread of cancer to another
organ or region of the body. Occurs when cancer cells break away from the main
tumor, travel via the blood or lymph and divide into new colonies of cancer
cells at distant sites. (Johnson 2012)
Malignant Tumors is cancer that metastasizes and
cancers that invade normal tissues until they compromise organ function.
2 Things must
happen simultaneously
1)
Cells
must grow and divide rapidly
2)
Cells
must undergo physical changes that allow it to break away from surrounding
cells.
18.3a. Mutant forms of proto-oncogens, tumor
suppressor genes, and mutator genes contribute to cancer
Several types of
genes control the various activities of a cell.
Structural genes code proteins for:
·
cell
growth
·
division
·
Differentiation
·
cell
adhesion
Regulatory genes code proteins that:
·
activate
or repress the expression of these structural genes
Growth
Inhibitors
·
regulates
cell division
Genes that
contribute to cancer:
·
Proto-oncogenes are normal
regulatory genes that promote cell growth, differentiation, division, or
adhesion. (Johnson 2012)
·
Mutated
proto-oncogenes are called oncogenes.
Oncogenes contribute to cancer.
·
Tumor Suppressor genes are
regulatory genes that under normal conditions regulate cell growth. When they
become damaged, they as well contribute to cancer.
Mutated genes
are involved in DNA repair during DNA replication. When these genes mutate, the
cell becomes prone to errors in DNA replication.
18.3b. A variety of factors can lead to cancer
All of these
factors change the cell’s DNA structure so that the genes responsible for
cell’s growth, differentiation, does not work.
A carcinogen is any substance or physical
factor that causes cancer. It is the process of transforming a normal cell into
a cancerous one.(Oellers, Online Presentation 2012)
Viruses and bacteria
·
reproduce
by inserting their DNA into the host’s DNA
·
impair
functions of a normal gene
Ex. (HPV) Human
Papillomovirus, Cervical Cancer, Hepatitis B and C, Liver Cancer, and HIV
Chemicals in the
environment
·
Asbestos
·
Benzene
·
Some
pesticides
·
Dyes
Tobacco
·
Most
Lethal
·
Contributes
to 30% of all cancer deaths
·
Lungs
·
Mouth
·
Pharynx
·
Pancreas
·
Bladder
Radiation
·
Sun
(Ultraviolent radiation)
·
Skin
cancer
·
Released
by rocks, soil and groundwater
·
Cell
phones, household appliances, power lines emit trace amounts of radiation.
·
High-frequency
ultraviolet B rays cause over 80% of all skin cancers
Melanoma is a
dangerous skin cancer of the melanin (pigment of the skin).
Diet
·
Raises
risk of cancer
·
Red
meat
·
Saturated
animal fat
·
Colon
·
Rectum
·
Prostate
gland
·
High
alcohol consumption
·
Breast
cancer
·
Liver
cancer
Internal Factors
Free
Radicals
·
Unstable
·
Produced
by body’s biochemical processes
·
Accumulate
and cause damage to tother molecules
·
Steals
electrons causes cells to fall apart
Antioxidants (Vitamins
A, C and E) appear to neutralize free radicals.
Afflatoxin is
present in foods, potent human carcinogen. Naturally occurring toxic metabolite
produced by certain fungi and mold found on food products such as corn and
peanuts. Potent liver carcinogen (oellers Online Presentation 2012).
18.3c. The immune system plays an important role in
cancer prevention
Immune System
·
Protects
us from cancer cells
·
Kills
cancer cells
Immune system suppression caused by
drugs, viruses such as HIV or even mental states of anxiety, stress, or
depression allows cancers to develop more easily
18.4 Advances in diagnosis enable early detection
Early detection
of cancer is an important key to success and that therapy can begin sooner,
hopefully before the cancer mestasizes.
18.4a Tumor Imaging: X-rays, PET, and MRI
X-Rays
·
Mamograms
·
Exposes
patient to radiation
PET (Positron-Emission Tomography)
PET scan of a brain
·
3-D
image
·
Shows
metabolic activity of body structures
·
Diagnoses
cancer
·
Study
blood flow
·
Heart
function
·
Brain
activity
·
Exposes
patient to radiation
MRI
·
Short
bursts
·
Magnetic
field
·
Detects
differences in water and chemical composition etween tissues
·
Detects
tumors
·
Produces
cross-sectional images of body structures
·
Does
not expose the patient to radiation
18.4b. Genetic testing can identify mutated genes
·
Identify
and detect mutated genes
·
Controversial
18.4c Enzyme tests may detect cancer markers
An enzyme called
telomerase is rarely found in normal cells, but is present in nearly all cancer
cells. (Johnson 2012).
18.5 Cancer Treatments
Cancer
treatments cure approximately 50% of all cancer cases.
18.5a. Conventional cancer treatments: Surgery,
radiation, and chemotherapy
Better
imaging techniques have benefited the surgical treatment of cancer, and
techniques for focusing external sources of radiation directly onto the cancer
have improved. (Johnson 2012).
Focused
sources of radiation damage and kill cancer cells in a specific location.
Healthy
cells recover from radiation more readily than cancer cells, but can injure or
kill some normal tissue.
A
drawback to both surgery and radiation is that they may miss small groups of
metastasized cells, allowing the cancer to reappear later.
Chemotherapy
is the administration of cytotoxic (cell damaging) chemicals to destroy cancer
cells (Johnson 2012).
Chemotherapy
·
Damage
to cells in digestive tract
·
Experience
nausea
·
Side
effects: hair loss, anemia, inability to fight infection
18.5b. Magnetism and Photodynamic therapy target
malignant cells
Magnetism
·
Powerful
magnet at the tumor site
·
Inject
tiny metallic beads into patient’s blood stream
·
Magnet
pulls beads (coated with Chemotherapy drug)
·
Kills
cancer cells
Photodynamic Therapy
·
Targets
cancer with light-sensitive drugs and lasers
18.5c. Immunotherapy promotes immune response
Immunotherapy
·
Boosts
immune system
·
Antibodies
that recognize cancer cells
·
Tagging
antibodies with radioactive molecules of chemotherapeutic drugs
·
Development
of vaccines against specific cancers
18.5d. “Starving” cancer by inhibiting angiogenesis
Angiogenesis is producing your own blood supply
which cancer does.
Tumors grow and
divide rapidly, requiring a lot of energy.
Tumors promote
angiogenesis (the growth of new blood vessels) to serve their energy needs.
Without angiogenesis,
the tumor would reach about the size of a pea and stop growing.
18.5e. Molecular treatments target defective genes
Molecular
treatments focus on specific defective genes. A key target for gene therapy is
p53, tumor suppressor gene that when defective, contributes too many cancers.
Target oncogenes
and repairs them to perform their specific function.
18.6 The 10 most common cancers
In both men and women,
the most frequent cancers are those of the skin, lung, and colon and rectum.
The most deadly
cancers are lung, colon and rectum and breast cancer.
18.6a Skin cancer: Look for changes in your skin
Researchers
say they may have discovered a new drug for the treatment of metastatic
melanoma, one that uses the patient's own tumor cells to customize the therapy. (Science Daily
2012).
Skin cancer
·
Melanoma
·
Nonmelanoam
(all other skin cancers)
Most common of
the nonmelanomas is basal cell carcinoma (cancer).
Rarely
metastasizes, but should be removed.
·
Squamous cell
cancer
arises from the epithelial cells produced by basal cells. May metastasize slowly.
·
Melanoma is the least
common and deadliest because this type of skin cancer mestastasizes quickly.
Melanoma is cancer of the melanocytes (cells that produce melanin that protects
cells from the sun). (Oellers Online Presentation 2012).
Early signs of
skin cancer (A,B,C,D,E’s Rule)
·
A= Asymmetry- the two halves
of the spot do not match.
·
B=Border- Irregular
shape.
·
C=Color- Varies or is
black
·
D=Diameter-Greater than
6mm (Pea)
·
E=Evolving=Gets larger
over time.
Basal and Squamous
cell cancers have a 95% cure rate if removed promptly because they metastasize
slowly if at all.
18.6b. Lung cancer: Smoking is leading risk factor
Symptoms of Lung
cancer
·
Persistent
cough
·
Recurrent
pneumonia
·
Bronchitis
·
Voice
change
Treatment
·
Surgery
often combined with radiation and chemotherapy
18.6c Breast cancer: Early detection pays off
First diagnosed
by a mammogram (an X-ray of breast tissue)
Abnormal lump on
breast
Research
suggests that there are two inherited susceptibility genes for breast cancer.
1)
BRCA1
2)
BRCA2
Biggest risk is
advancing in age.
18.6d. Prostate cancer: Most common after age 50
Symptoms
·
Difficulty
urinating or inability
·
Blood
in urine
·
Pain
is pelvic area
Biggest risk is
advancing in age.
Detected By
·
Digital
rectal exam
·
(PSA)
Prostate-Specific antigen test (Detects elevated blood levels of a protein
produced by the prostate gland when prostate cancer is present).
Treatment
·
Surgery
·
Radiation
·
Hormones
18.6e. Cancers of colon and rectum: Tests can detect
them early
Signs
·
Blood
in stool
·
Rectal
bleeding
·
For a screening test,
they use a colonoscopy.
Most colorectal
tumors begin with polyps.
Polyps are small benign growths that develop
from the colon lining.
Treatment
·
Polyp
Removal
·
Tumor
Removal
18.6f. Lymphoma: Cancers of Lymphoid tissues
Symptoms
·
Enlarged
lymph nodes
·
Intermittent
fever
·
Itching
·
Weight
loss
·
Night
sweats
Risk factors are
not entirely clear but seem to relate to altered immune function.
18.6g. Urinary bladder cancer: Surgery is often
successful if done early
A sign is blood
in the urine.
Treatment
consists of surgery with chemotherapy.
18.6h.Kidney cancer: Detected during examination for
a renal-related problem
Risk Factors
·
Heritable
gene mutations
·
Smoking
·
Exposure
to certain toxic agents (smokeing, asbestos and cadmium)
·
Cancer causing
agents and toxic chemicals are more likely to affect the kidneys than many
other organs, because as the kidneys concentrate the urine, they also
concentrate the toxic agents in it. (Johnson 2012).
Can be tested by
using a CT scan or ultrasound.
Treatment is
removal of the infected kidney.
18.6i. Cancer of the uterus: Unusual uterine
bleeding is major symptom.
Risk factor for endometrial
cancer is a lifetime of high exposure to estrogen. Ex. Early menstrual cycle,
late menopause, obesity, not having children and estrogen replacement therapy
after menopause.
Treatments include surgery, radiation, hormones or
chemotherapy.
18.6j. Leukemia: Chemotherapy is often effective
Leukemia is
cancer of immature white blood cells in bone marrow.
A diagnosis
could be made with a blood test or bone biopsy.
Treatment includes chemotherapy and maybe a bone
marrow transplant to replace the normal blood-forming stem cells eliminated by
chemotherapy.
At least 60% of
all cancer cases other than nonmelanoma skin cancers are thought to be caused
by just two factors:
1)
Smoking
2)
Poor
Diet
Smoking is by
far the leading risk factor for cancer.
Strategies to
reduce your own risk of cancer
·
Know
family history
·
Know
your body
·
Get
regular medical screenings
·
Avoid
sunlight and sunlamps without the use of sunscreen
·
Watch
diet and weight
·
Drink
alcohol in moderation
References
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
2012, from http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
Science Daily (March 8, 2012).
Promising New Drug Could Help Patients Battling Deadly and Difficult to Treat
From of Melanoma. Retrieved March 10, 2012, from
Chapter 19
Genetics and Inheritance
Table of
Contents
19.1 Your
genotype is the genetic basis of your phenotype
19.2 Genetic
Inheritance follows certain patters
a. Punnett square analysis predicts
patterns of inheritance
b. Mendel established the basic
principles of genetics
c. Dominant alleles are expressed
over recessive alleles
d. Two-trait crosses Independent
assortment of genes for different traits
19.3 Other
dominance patterns
a. Incomplete dominance: Heterozygote’s
have an intermediate phenotype
b. Codominance: Both gene products
are equally expressed
19.4 Other
factors influence inheritance patterns and phenotype
a. Polygenic inheritance: Phenotype
is influenced by many genes
b. Both genotype and the environment
affect phenotype
c. Linked alleles may or may not be
inherited together
19.5 Sex-linked
inheritance: X and Y chromosomes carry different genes
a. Sex-linked inheritance depends on
genes located on sex chromosomes
b. Sex-influenced traits are
affected by actions of sex genes
19.6 Chromosomes
may be altered in number or structure
a. Down syndrome: Three copies of
chromosome 21
b. Alterations of the number of sex
chromosomes
c. Deletions and translocations
alter chromosome structure
19.7 Many
inherited genetic disorders involve recessive alleles
a. Phenylketonuria is caused by a
missing enzyme
b. Tay-Sachs disease leads to brain
dysfunction
c. Huntington disease is caused by a
dominant-lethal allele
19.8 Genes code
for proteins, not for specific behaviors
19.1 Your
genotype is the genetic basis of you phenotype
Genotype is a complete
set of alleles. Genotype is the genetic basis of phenotype.
Phenotype is the physical
and functional traits that characterize you.
Ex.
Hair, eyes, skin color, height, body shape, etc.
Picture of autosomes from a female
We
have 22 autosomes, which may look alike, but may not be identical.
Small differences in DNA sequence may exist
between any pair of autosomes.
These
sequence differences may occur within genes, and when they do, they produce
alternative versions of genes called alleles.
Because they are different, alleles may code for different proteins with
slightly different structures. Alterations in protein structure can affect how
the protein functions. Ex, The ability to roll your tongue is influenced by a
single gene.
We
inherit two alleles of every gene found on autosomes; these alleles may be
identical or slightly different. The sum of our alleles is our genotype and the physical and
functional expression of those alleles is our phenotype.
A homologous allele
If
an individual possesses two identical
alleles of a particular gene, the person is homozygous.
A
person who has two different alleles
of a gene is heterozygous.
Different
alleles resulted from mutations or random changes to the DNA sequence, of cells
destined to become sperm or eggs.
All
the various genes and their alleles in the human population are known as the human gene pool (Johnson 2012).
19.2 Genetic inheritance follows certain patterns
19.2a Punnett
square analysis predicts patterns of inheritance
A
punnett square provides a way to
represent patterns of inheritance of alleles and to predict the probability of
alleles that a particular genotype will be inheriting (Johnson 2012).
19.2b. Mendel
established the basic principles of genetics
In
1850, Gregor Mendor and Austrian monk came up with the Law of Segregation and
the Law of Independent Assortment.
Law of segregation says that when
gametes form in the parents, the alleles separate from each other so that each
gamete gets only one allele of each gene.
Law of
Independent Assortment is genes for different traits that are separated
from each other independently during meiosis. This also applies for genes on
different chromosomes. (Oellers Online Presentation 2012).
19.2c Dominant
alleles are expressed over recessive alleles
Dominant allele makes or
suppresses the expression of its complementary allele.
Always
expressed heterozygous.
Recessive allele will not be
expressed if paired with a dominant allele (heterozygous).
Will
only be expressed if individual is homozygous for the recessive allele.
Dominant
alleles are not always more common than recessive, sometimes they may be rare
in a population (Oellers Online Presentation 2012).
19.2d. Two-trait
crosses: Independent assortment of genes for different traits
Two-trait
cross- each parent donates only one allele of each gene, the genes for
different traits assort independently of each other during the formation of the
gametes.
When
two alleles of each gene exist in the human gene pool, one is often dominant
over the other and controls the phenotype of a heterozygote.
19.3 Other
dominance patterns
19.3a. Incomplete
dominance: Heterozygote’s have an intermediate phenotype
Incomplete
dominance
·
Do
not follow dominant/recessive pattern. Neither gene is dominant
·
Heterozygous
genotype in a phenotype is intermediate between the two homozygous phenotypes.
Ex. Father has
straight hair, mother has wavy hair and their offspring will have curly hair.
Codominance is the product of both alleles that are
expressed equally (Johnson 2012).
Ex. Blood Type
Type A can have
AA or AO
Type B can have
BB or BO
Type AB is AB
only
In addition,
Type O can have OO. People with this blood type are universal donors.
There are three
alleles for this gene: A, B and O
A gene and B
gene are codominant
Ex Sickle cell anemia
(Hbs Hbs) (Homozygous)
19.4 Other Factors influence inheritance patterns
and phenotype.
19.4a. Polygenic inheritance: Phenotype is
influenced by many genes
Polygenic
inheritance of phenotypic traits depends on many genes.
At least three
genes control eye color.
19.4b. Both genotype and the environment affect
phenotype
Ex. Environmental
influence is the effect of diet, height and weight and body size.
Usually we
inherit a slight increase risk of developing a disease, with those risks
modifiable by the environmental factors and our own actions.
Your genes carry
the instructions for all your proteins, but the environment can influence how
genes are expressed and how they contribute to your phenotype.
19.4c. Linked alleles may or may not be inherited
together
Linked alleles are alleles for different traits
inherited and that travel together because they are physically joined on the
same chromosome.
They are not always
inherited together because of crossing-over, which partially reshuffles alleles
across each pair of autosomes during meiosis.
Alleles located
close to each other have a good chance of being inherited together.
19.5 Sex-linked inheritance: X and Y-chromosomes
carry different genes.
Kayotype is a composite display of all the
chromosomes of an organism.
Chromosomes are
identifiable in cells only just before cell division.
Chromosomes are
identified and paired according to their size, centromere location and
characteristic bonding patterns.
A number
arrangement of all 23 pairs of chromosomes is called the human karyotype (Johnsons 2012).
The advantage of
having pairs of autosomes is that you have two copies of each gene. If
something goes wrong with one copy, the other one can still carry out its
function.
Sex-linked inheritance is inheritance
patterns that depend on genes located on the sex chromosomes.
Sex linked inheritance is x-linked if
the gene is located only on the X chromosome and Y-linked if the gene is
located only on the Y chromosome (Oellers Online Presentation 2012).
Genes occur in
pairs.
19.5b. Sex-influenced traits are affected by actions
of sex genes
Genes encoding
these traits are located on autosomes not sex chromosomes.
Ex. Baldness
Testosterone
stimulates the expression of male baldness allele, converting it from recessive
to a dominant allele in males. This is an example of a sex-influenced
phenotype, one not inherited with the sex chromosomes per se, but influenced by
the actions of the genes on the sex chromosomes. (Johnson 2012).
19.6 Chromosomes may be altered in number or structure
http://medical-dictionary.thefreedictionary.com/_/viewer.aspx?path=dorland&name=nondisjunction.jpg accessed
March 10, 2012
This is a
picture of Nondisjunction. Normal meiosis (A) is contrasted with failure
of homologous chromosomes to separate in meiosis I (B) or of sister
chromatids to separate in meiosis II (C).
Nondisjunction happens during meiosis. It is the
failure of the homologous chromosome or sister chromatids to separate properly.
Resulting in an alteration in the chromosome number or gametes.
Ex. Down
Syndrome and other syndromes
19.6a. Down Syndrome: Three copies of chromosome 21
A few
alterations of autosomal chromosome number do result in live births.
The most common
is Down Syndrome cause by inheriting an extra copy of chromosome 21.
19.6b. Alterations of the number of sex chromosomes
Nondisjuction of
the sex chromosomes can produce a variety of combinations of sex chromosome
number, several of which are common in the human population.
The four most
common alterations of sex chromosome number are:
·
XYY-Jacob
syndrome
·
XXY
Klinefelter syndrome
·
XXX
Trisomy-X syndrome
·
XO
Turner Syndrome
XYY Jacob syndrome
·
Tall
males
·
Fairly
normal
·
Impaired
mental functions
XXY Klinefelter syndrome
·
Tall
male
·
Sterile
·
Mild
mental impairment
·
May
develop large breasts
XXX Trisomy-X Syndrome
·
Female
·
Mild
mental retardation
XO Turner Syndrome
·
female
·
short
·
slightly
altered body form
·
small
breasts
·
not
mentally retarded
·
sterile
·
Possess
only one X chromosome.
19.6c. Deletions and translocations alter chromosome
structure
Deletion occurs when apiece of chromosome breaks
off and is lost resulting in few live births.
Translocation occurs when a piece of a chromosome
breaks off, but reattaches at another site, on the same chromosome or another.
19.7 Many inherited genetic disorders involve
recessive alleles
People express
inherited genetic disorders caused by recessive alleles only if they inherit
two of the defective alleles.
Ex. of a
Recessive genetic disorder is Cystic Fibrosis
19.7a Phenylketonuria is caused by a missing enzyme
A human
inherited disease in which homozygous recessive individuals are unable to make
an enzyme that is needed for normal metabolism of phenylalanine and amino acid.
High concentrations
of phenylpyruvic acid can lead to mental retardation, slow growth rate and
early death.
19.7b. Tay-Sachs disease leads to brain dysfunction
Enzyme
deficiency disease caused by a recessive gene located on Chromosome 15.
19.7c. Huntington disease is caused by a
dominant-lethal allele
This disease is
always lethal and is marked by a progressive nerve degeneration leading to
physical and mental disabilities.
Genetic testing
is one of the benefits of the human Genome Project.
19.8 Genes code for proteins, not for specific
location
Genes do not
cause specific behaviors.
Proteins may act
as hormones, neurotransmitters, enzymes or intracellular messengers.
Together groups
of genes and their protein product do influence broad patterns of behavior.
Ex. Feeding,
mating or learning
Scientists have discovered that men respond more aggressively than women to stress because of a single gene. Science Daily (Mar. 8, 2012) state in their article say Australian scientists, believe the SRY gene, which directs male development, may promote aggression and other traditionally male behavioral traits resulting in the fight-or-flight reaction to stress. Scientists have also found the SRY protein in vital organs in the male body, including the heart, lungs and brain, suggesting SRY exerts male-specific effects that play a vital role in direct response to stree.
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
2012, from http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
Science Daily (March 8, 2012). Men
Respond More Aggressively Than Women to Stress and It’s All Down to a Single
Gene. Retrieved March 10, 2012, from
Chapter
20
DNA
Technology and Genetic Engineering
Table of Contents
20.1 DNA sequencing reveals structure of
DNA
20.2 DNA can be cloned in the laboratory
a. Recombinant DNA technology:
Isolating and cloning genes
b. Cloning DNA fragments: The
polymerase chain reaction
c. Identifying the source of DNA:
DNA fingerprinting
20.3 Genetic Engineering creates
transgenic organisms
a. Transgenic bacteria have many
uses
b.Transgenic Plants: More vitamins
and better pest resistance
c. Transgenic animals: A bigger
challenge
20.4 Gene therapy: The hope of the
future
a. Gene therapy must overcome many
obstacles
b.Vectors transfer genes into human
cells
c. Success with SCID gives hope
d.Research targets cystic fibrosis
and cancer
20.1 DNA sequencing reveals structure of
DNA
DNA
sequencing can determine the nucleotide sequence of short pieces of DNA.
·
Millions of copies of identical copies of a piece of DNA strand is
put in a test tube
·
Primers
(short strands of DNA that bind to one end of DNA to be sequenced) are added
·
Primer is the beginning point for synthesis of new strand
·
Four nucleotides plus four nucleotides that have been modified are
added
·
Added is an enzyme called DNA
polymerase (enzymes that will allow the replication of DNA molecule by
separating strands (Oellers, Online presentation 2012))
·
Synthesis begins
During
synthesis, the result of the mixture is of pieces of DNA varying in length.
The
pieces are placed on a column of gel and subjected to a process called gel electrophoresis (Johnson 2012).
The
DNA pieces move through the gel and are arranged in order by the size of the
pieces as the DNA pieces exit the gel. This represents the sequence of a single
strand of DNA.
20.2 DNA can be cloned in the laboratory
In
the last few decades, scientists have learned how to recombine DNA and develop
organisms never before created in nature and maybe even the ability to modify
or fix defective human genes.
20.2a. Recombinant DNA technology:
Isolating and cloning genes
Cutting,
splicing and copying (cloning) DNA and the genes it contains is called
recombinant DNA technology (Johnson 2012).
The
goal is to transfer pieces of DNA from one organism into another.
Used
to insert specific genes into bacteria so that the bacteria can be induced to
produce useful protein products.
Requires
specialized tools:
·
Restriction Enzymes
·
DNA ligases
·
Plasmids from bacteria
Restriction Enzymes are
naturally occurring enzymes in some bacteria that breaks the bonds between
specific neighboring base pairs in a DNA strand.
Most
effective is bacteria that will cut the double stranded DNA in the palindrome area.
Palindrome is
a sequence of letters that reads the same backward as forward, for example,
racecar (Johnson 2012).
DNA ligases are
enzymes that bind fragments of DNA back together after the restriction enzymes
have cut them.
Plasmids are
small, circular, self-replicating DNA molecules found in bacteria.
Plasmids
are useful because they can be made to incorporate a foreign piece of DNA. Once
the plasmid is reinserted into the bacterium, it is copied every time the
bacterium reproduces.
20.2b. Cloning DNA fragments: The
polymerase chain reaction
The polymerase chain reaction is used to
make millions of copies of a small fragment of DNA very quickly (Johnson 2012).
Polymerase
is not useful for cloning whole genes, because it lacks the regulatory genes
and proteins required to activate genes.
20.2c. Identifying the source of DNA:
DNA fingerprinting
DNA fingerprinting is
the technique for identifying the source of a fragment of DNA after it has been
sufficiently copied by PCR (Polymerase chain reaction).
Process
·
DNA sample amplified by PCR
·
Restriction enzymes cut the DNA
·
DNA separated by gel electrophoresis
·
Fragment pattern is compared to original DNA sample
20.3 Genetic Engineering creates transgenic
organisms
Transgenic
organisms are genetically engineered so that they carry one or more foreign
genes.
20.3a. Transgenic bacteria have many
uses
Can
Produce
·
Human proteins
·
Human Hormones
·
Vaccines
·
Insulin
20.3b.
Transgenic plants: More vitamins and better pest resistance
Transgenic plants and animals can provide new agricultural crops
and useful human proteins.
Transgenic plants may: (Oellers Online
Presentation 2012)
·
Improve nutrition (Controversial)
·
Produce Vaccines
·
Synthesize Hormones
·
Resist Freezing
Concerns:
·
Gm crops hybridizing with natural crops, devaluing them (Oellers
Online Presentation 2012)
·
Crop Failure
20.3c. Transgenic animals: A bigger
challenge
http://listverse.com/2008/04/01/top-10-bizarre-genetically-modified-organisms/ accessed March 10, 2012
The GloFish was the first
genetically modified animal to become available as a pet.
Gene Parming is
a process of producing proteins in farm animals for medical uses.
Developed
to:
·
Participate in medical research
·
Gene “pharm” drugs from milk
Challenges/Concerns
·
More difficult to introduce foreign DNA to animal cells
·
Cloning more difficult
·
Too close to human cloning?
·
Endangered species and extinct species cloning could be beneficial
20.4 Gene therapy: The hope of the
future?
Gene therapy is
the insertion of human genes into human cells to treat or correct disease.
ScienceDaily (Mar. 8, 2012) states in their article that the UT Southwestern
Medical Center investigators have identified a genetic manipulation that
increases the development of neurons in the brain during aging and enhances the
effect of antidepressant drugs. This work suggests that activating neural precursor cells
could directly improve depression- and anxiety-like behaviors, and it provides
a proof-of-principle regarding the feasibility of regulating behavior via
direct manipulation of adult neurogenesis. Studies that link the Nf1
gene are
best known for mutations that cause tumors to grow around nerves and effects several
major tissues. For instance, in one study researchers identified ways that the
body's immune system promotes the growth of tumors, and in another study, they
described how loss of the Nf1 protein in the circulatory system leads to
hypertension and congenital heart disease. (ScienceDaily 2012)
20.4a. Gene therapy must overcome many
obstacles
Transgenic
animals are created by inserting a gene into a single cell (fertilized egg)
that has been isolated for microinjection.
An
individual has trillions of differentiated and matured cells this makes the use
of gene therapy very difficult.
20.4b. Vectors transfer genes into human
cells
A
class of viruses called retroviruses;
they splice their own RNA based genetic code permanently into the DNA of the
cells they infect.
Human
genes can be packaged in retroviruses, which can introduce genes to human
cells.
2
strategies for gene transfer is getting the gene into
enough living cells to produce enough of the missing protein to prevent the
disease.
1) Human cells of a target tissue is removed and
exposed to the retrovirus containing the human gene of interest. The hope is
that the virus-infected cells will incorporate themselves back into the tissue
and express the missing protein.
2) Inject
the retrovirus with their human gene payload directly into the patient.
Downside
to retrovirus
·
Insert foreign DNA into a cell’s DNA only when the cell is
dividing
·
Insert their genetic material randomly in the genome
·
Can disrupt the function of other human genes
20.4c. Gene Therapy Successes
·
Sever
combine immunodeficiency (SCID)
Have had some success with gene therapy.
SCID is a genetic disorder of the immune system that occurs when
the T-lymphocyte system does not function properly.
·
Cystic
fibrosis
Minor success
·
Cancer
Research
·
Blindness
Gene
therapy is still more of a hope than a reality. Even if scientists are able to
correct genetic disease in an individual that person’s child could still
inherit the disorder.
REFERENCES
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
2012, from http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
ScienceDaily
(Mar. 8, 2012). Genetic Manipulation Boosts Growth of Brain Cells
Linked to Learning, Enhances Effects of Antidepressants. Retrieved March 10,
2012, from
