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GENETICS 310
EXAM II
April 25, 2017
I. Using D for DNA repair defects, O for oncogene R for retrovirus, and T for tumor
suppressor, place the appropriate letter(s), if any, in the blank before each character or
example listed.
T
The RB (retinoblastoma) gene
D
Xeroderma pigmentosum
O
Over-expression associated with cancer
O
May be carried by a retrovirus
R
HIV (he AIDS virus)
D, O, R, T
Associated with increase risk of cancer
T
Cancer often involves an inherited and a somatic cell mutation
T
P53 is one such gene
O
More common problem in chickens than man
O
Translocated in Burkitts lymphoma
HPV (Human papilloma virus)
II. a) Write the letter(s) of each of these pedigrees (shaded means affected) that could
possibly occur with the listed modes of inheritance?
c, e, f
Sex linked dominant
a
Holandric
a,b
Sex linked recessive
f
Cytoplasmic
a
Sex limited
b) Using M for male, F for Female, - for sterile and + for fertile describe the following
syndromes. Also show the sex composition and total chromosomes in the karyotype.
Sex / Fertility
Sex Chromosomes Total Chromosome #
M/+
Jaccob’s
XYY
47
F/+
Triplo X
XXX
47
F/-
Turner’s
XO
45
M/-
Klinefelters’
XXY
47
M/-
Downs male
XY
47
c) Tell whether the following are associated with Lyons Law (L), Genomic Imprinting (G).
both (B), or neither (N).
G
Sex-specific silencing of specific genes in eggs or sperm
L
Calico cats
N
Complete androgen insensitivity (testiular feminization)
N
Pattern Baldness in humans
L
Random inactivation of an X chromosome early in embryology
G
Prader-Willi syndrome
B
Involves shutting down gene expression
N
Shell coiling in snails
III. In maize P_ is plump kernel and pp is shrunken, while Y_ is yellow seed and yy is
white. A testcross gave 100 progeny in the ratio 47 plump, yellow : 3 plump, white :
2 shrunken, yellow : 48 shrunken, white.
a) Are the genes linked?
yes
If so, at what map distance?
b) Show the genotypes of the two parents.
P5Y
p y
c) Are the genes syntenic Yes
p
p
5 cM
y
y
Whether yes or no, how do you know?
Must be on same chromosome if linked
IV. 1) Given that a normal rice pollen nucleus has 12 chromosomes:
a)
1N
is the ploidy level of a rice pollen grain.
b)
24
chromosomes would be found in a rice leaf cell? Its ploidy is
c)
36
chromosomes would be found in somatic cells of a triploid rice plant.
d)
23
chromosomes would be found in somatic cell of a monosomic rice plant.
2N
2) In general:
e)
f)
bread wheat
banana
Is an example of a hexaploid plant that is also an amphidiploid.
is an example of a plant that is grown as a triploid.
g)
Trisomy 21
is the most common non-sex numerical chromosome aberration
to survive in humans.
V. Using D for deletions, A for additions, (duplications) Pa for paracentric inversions, Pi
for pericentric inversions and T for translocations, tell which is/are associated with the
following: (In some cases D or A were accepted, but the following were expected:)
D
(D) Pa, Pi, T
Cri du chat in humans
Causes loss of fertility in heterozygotes
A
Explains barr-eyes in Drosophila
T
Cross-shaped configuration during synapsis
Pa, Pai
Internal crossovers cause defective gametes
T
Rare cases of ‘inherited’ trisomy 21
T
Gametes fertile when alternate segregation occurs
Pa
More detrimental in males than females
Pa, Pi
Pairing requires a loop within a loop.
A
Source of new genes
Pa, Pi, T
Associated with creation of new species via problems in meiosis
A, Pa, Pi, T
Seldom associated with a specific phenotype
Pa, Pi, T
May lead to alternate gene maps
Pa
Crossover leads to formation of ‘bridges’ in Meiosis 1.
VI. It has been observed that 75% of the wild sheep on a Scottish Island of St. Kilda
have black wool and 25% have white wool. a) Assuming black wool is a single gene
dominant, what are the frequencies of the B and b alleles in this herd?
F(B) = 0.5, F(b) = 0.5
b) Predict the genotypic ratio in the herd.
25 BB: 50 Bb : 25 bb
c) What assumption did you make to do part b? Random mating
d) it has also been observed that the relative frequency of black sheep on the island is
gradually decreasing. What force or forces might account for the change?
Selection; drift if the population is small
VI. Provide the term that fits the following descriptions:(lots of other examples for many)
bottleneck
10-3 or 0.001
1
migrration
Sickle cell
Tay Sachs
amniocentesis
spina bifada
Huntingtons
Cystic fibrosis
VNTR or Jeffries
CVB or CVS
inbreeding
Selection
Sickle cell
PCR
Founder effect
Trisomy 21 etc
Mutation
SSRs or STRs
Mitochondrial DNA
Inbreeding
is when a large population is reduced to a few individuals.
is the equilibrium frequency of a recessive lethal maintained
by new mutations at the rate of 1 in a million (1 X 10-6).
Is the number of generations needed to remove a dominant
lethal mutation from a population.
is a force in population genetics that leads to ‘gene flow’.
is a recessive genetic disease that can be detected in utero
only with DNA-based tests.
Is a disease that can be detected in utero using an enzyme
assay.
is a relatively safe procedure that provides fetal cells and
byproducts 15-16 weeks into a pregnancy.
Is a non-genetic condition that can be detected in utero due
to the presence of α−feto protein.
Is an example of a tri-nucleotide repeat disease for which
risk can be measured from in utero samples using PCR.
is a recessive disease where many different mutant alleles
are known, making prenatal detection difficult.
are DNA ‘probes’ sometimes used in forensics for making
Southern blot DNA fingerprints
is a procedure for collecting fetal cells around 8 weeks into
the pregnancy.
causes the frequency of heterozygotes to drop and the
frequency of homozygotes to increase.
is the force that led to pigment differences in moths in
industrial versus rural regions of England.
is a disease where heterozygotes have a reproductive
advantage in areas with high incidence of malaria.
is a process for amplifying DNA between two flanking
primers.
is when a new population is started with a few individuals.
is a syndrome that can be detected in utero based on
karyotype analysis.
Is a force that can cause gene frequencies over generations
extremely slowly.
are relatively variable sequences that make good markers
for use in forensics.
polymorphisms can be used to track maternal heritage.
increases the risk of detrimental homozygous recessives
showing up in families.