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II. True or false:
F
The Rb gene is an example of an oncogene.
T
Over-expression of oncogenes can lead to cancer.
F
Most cancer cells have just a single gene defect.
T
Inheriting one defective Rb allele leads to a very high risk of retinoblatoma.
T
Xeroderma pigmentosum leads to cancer as a result of defective DNA repair.
F
The normal function of a tumor suppressor gene is to slow tumor growth.
T
The src gene identified in chickens is also found in humans.
T
Most retrovirus-induced cancers occur when an onc gene is in their genome.
T
HPV is a DNA virus associated with cervical cancer in humans.
T
Radiation and UV sensitivity result from defects in different repair genes.
T
v-onc and c-onc genes turn out to be the same genes.
T
Burkitts lymphoma is associated with a virus and a common translocation.
III. a) Using F for fertile, S for sterile, F for female, M for male, T for taller, S for shorter,
and showing the number of X and Y chromosomes, fill in the missing information for
the six different aberrations in the table below:
Name
Fertility
Sex
Height
X/Y comp.
1.Triplo X
F
F
T
XXX
2.Turners
S
F
S
XO
3. Jacobs or XYY
F
M
T
XYY
4.Klinefelters
S
M
T
XXY
5. Downs male
S?
M
S
XY
6. complete androgen ins or ‘TFM”
S
F
T?
XtfmY
b) Which case(s) (by number) would be expected to have very reduced IQ?
IV. Check the following that are part of, or consequences of the Lyon Law:
X
Triplo X female cells have 2 Barr Bodies.
X
After it occurs, the same X is inactivated in mitotic daughter cells.
X-inactivation preferentially affects the X from the father.
X-inactivation occurs at the time of meiosis.
One Y in an XYY individual is also inactivated.
X
Calico cats are (almost) always females
Different regions of the X are inactivated in different cells.
5
V. a) Plant species X has 24 chromosomes per somatic cell and species Y has 26. One is
an autotetraploid and the other an allotetraploid. Which is the autotetraploid and how
do you know? Using A and B for genomes, show the composition of each.
Auto = 24: four sets of 6 AAAA, allo is AABB where b has 7 chromosmes
b) In an organism where gametes have 10 chromosomes, how many chromosomes
would be present in the somatic cells of:
a trisomic
21
a triploid
30
c) A hybrid is created between mice with genes on chromosome 1 in the order
A
B • C
( • is the centromere)
D E F and A
E
D
C •
B F
Show meiotic pairing in the hybrid mouse.
Estimate the fraction of fertile gametes a female hybrid will produce
50%
d) Give two cases where the risk of a trisomy 21 birth in humans is elevated.
1.
2.
e) Humans have 46 chromosomes per diploid cell and chimps have 48. Still, the species
are considered to be very closely related. What accounts for the numerical difference
and what suggests ‘close relationship’.?
The apes have 2 one armed chromsomes that fused (Robertsonian translocation to
become one human biarmed chromosomes. Relationship is suggested by very similar
DNA sequences and gene order, banding etc. in the chromosomes,
VI. Use a line drawing of paired chromosomes to show the difference between a
pericentric and paracentric chromosomal inversion.
VIII. a) Give an example of a genetic disease that can be detected prenatally:
Via an enzyme assay
Tay Sachs
By PCR amplification from primers flanking a trinucleotide repeat Fragile X,
Huntingtons
Only at the DNA level
By making a karyotype
Sickle Cell
trisomy 21 etc
b) What is the basis for the hypervariability of the loci entered in CODIS by the FBI?
Simple Sequence Repeats 1°
VII. Only 4% of the mice in a population in one population are white, which is the
homozygous recessive (bb) color; the others are brown.
a) Predict the B and b allele frequencies, as well as the BB, Bb and bb frequencies.
F(B)= 0.8
F(b)= 0.2
F(BB)=
64%
F(Bb)=
32%
F(bb)=
4%
b) What assumption did you make in calculating the genotype frequencies?
Random mating
c) What would happen if white mice were seldom involved in mating? What force
would be involved? Frequency of b allele would diminish selection