GENETICS - BIOL 7 EXAM II - October 24,
2002 NAME:
DO NOT USE ANY OTHER PAPER AT ANY TIME WITHOUT INSTRUCTOR PERMISSION
Part I: [42 points] Choose the one BEST answer. Circle its
letter. Read each question and all 5 choices carefully because more
than one answer might seem correct at first glance. 1.5
points each
1. p 5 r
20 t. What frequency double cross-over
gametes is expected?
a. 1%
b. 2%
c. 10%
d. 20%
e. can not be estimated
2. What is the probability of 3 male offspring in a family of 9?
a. 36/512
b. 84/512
c. 1/512
d. 84/1024
e. 3/9
3. Sister chromatids are separated from one another during
a. prophase
b. metaphase
c. anaphase
d. telephase
e. any of the above - depending on
circumstances; sometimes one brother organizing the others
4. Two genes are known to be 15 map units apart. The expected
percentage of nonparental (recombinant) offspring from a test cross is
a. 30%
b. 15%
c. 7.5%
d. 1.5%
e. not enough information given
5. In a dihybrid involving two different genes on two different
pairs of chromosomes, the recombinant frequency will be:
a. 0%
b. 10%
c. 25%
d. 50%
e. 100%
f. none of the above; there is no
recombination between genes on different chromosomes
6. A triply wild-type female mated with a triply recessive mutant
male gives rise to a large number of offspring. All of the
offspring are wildtype. Among the F-1, the males represent many
different phenotypes, but the females are all wildtype. This
indicates
a. the genes are sex-linked; the mother (P1)
was heterozygous at several loci
b. the genes are sex-linked; the mother (P1)
homozygous dominant
c. the genes are sex-linked but this is a
ZZ/ZW organism: the female is hemizygous
d. the genes are autosomal
e. not enough information given
7. A male of unknown genotype crossed with an [aa ] female yields
progeny phenotypes: 24 A male, 26 A female, 23 a male
and 27 a female; the best explanation is that
a. the gene is lethal in homozygous dominant
form
b. the gene is probably on the X chromosome
c. the male parent is heterozygous at the A
locus
d. the A gene represents color blindness
e. the A gene is recessive
8. A plant breeding true with purple flowers is crossed to a
plant breeding true with white flowers. All the offspring had
purple flowers. The most likely explanation is
a. co-dominance
b. partial dominance
c. epistasis
d. purple is completely dominant
e. it is not possible to tell until the F2 is
observed
9. Sister chromatids are separated from one another during
a. anaphase of mitosis
b. anaphase I
c. anaphase II
d. a and b
e. a and c
10. To determine the distance between three genes, a,b, and c,
a. only one dihybrid cross is necessary
b. two different dihybrid crosses are
necessary: a - b and b - c
c. three dihybrid crosses are necessary: a-b,
b-c, and a-c
d. each of these genes must be mapped with
respect to a fourth gene, d
e. one cannot map three genes using dihybrid
crosses
11. What is the probability that the first 3 offspring in a
family of 9 will be male, and the rest will be female?
a. 3/9
b. 3/512
c. 84/512
d. 1/512
e. 18/512
12. As the distance between two loci increases, mapping
them becomes
a. more affected by interference
b. less accurate
c. easier to calculate
d. more accurate
e. a and b
f. c and d
13. Rh blood types are an example of a phenotype controlled by
a. multiple genes
b. codominance
c. multiple alleles
d. a and b
e. all of the above
14. Non-recombinant gametes
a. are gametes that are physically unable to
recombine
b. should represent less than 50% ( <50%
)of the total observed genotypes
c. should represent more than 50% ( > 50% )
of the total observed genotypes
d. are gametes which are present on different
chromosomes
e. are representative of the parental
generation
15. Mitosis in in a haplod cell yields
a. 2 daughter cells with genotypes that are
the same as each other and as the original cell
b. 2 daughter cells with genotypes that are
different from the original cell
c. 4 daughter cells with genotypes that are
the same as each other and as the original cell
d. 4 daughter cells with genotypes that are
different from the original cell
e. none of the above
16. In a dihybrid testcross, the RF will be
a. 50% - 100% for linked and unlinked genes
b. 0 - 50% for linked and unlinked genes
c. 50% - 100% for linked genes only
d. 0 - 50% for linked genes only
e. it is not possible to generalize this way
17. Interference is
a. the occurrence of no crossovers in meiosis
b. nondisjunction of the X chromosome at 1st
division meiosis
c. nondisjunction of the X chromosome at 2nd
division meiosis
d. when a crossover event in one region of the
chromosome inhibits a second event in nearby regions
e. nondisjunction in mitosis
18. If the genes above are linked, which mating would allow the
best mapping?
a. the F-1
b. the female F-1 with the P-1 male
c. the female P-1 with the F-1 male
d. one would have to find another strain
altogether - none of these are helpful
e. the genes are not linked
19. In Drosophilla, if a red eyed female (wild type, + +) is
crossed with a white-eyed male (w), in which generation does it become
clear that w is sex linked?
a. P
b. F1
c. F2
d. not enough information
e. this cross does not demonstrate the
sex-linkage of w
20. If genes Y and P are 64 map units apart, what proportion of
progeny would be expected to be Yp or yP when YP / yp is testcrossed?
a. 0%
b. 32 %
c. 50 %
d. 64 %
e. 100 %
21. Multiple alleles can only be studied in
a. mutations
b. inheritance
c. blood groups
d. antigens
e. populations
22. The ABO blood groups are an example of a phenotype resulting
from
a. multiple alleles
b. codominance
c. multiple genes - epistasis
d. a and b
e. all of the above
23. A heterogametic female is represented by which of the
following?
a. XY
b. ZW
c. XX
d. ZZ
e. a and b
f. b and c
g. none of the above
24. Homologous chromatids are separated from one another during
a. anaphase of mitosis
b. anaphase I
c. anaphase II
d. a and b
e. a and c
25. Meiosis in in a haplod cell yields
a. 2 daughter cells with genotypes that are
the same as each other and as the mother
b. 2 daughter cells with genotypes that are
the different from the mother
c. 4 daughter cells with genotypes that are
the same as each other and as the mother
d. 4 daughter cells with genotypes that are
the same as each other and as the mother
e. none of the above - haploid cells can
not undergo meiosis
26. What is the probability of 4 dominant offspring in a total of
7 offspring from a monohybrid cross?
a. 35 * 34 / 47
b. 35/ 27
c. 3/4
d. (34 / 47) * (13 / 47)
e. (34 * 13)/ 47
27 - 28. The cross of XAXa and XAY yields [for each, indicate T
or F: ]
a. all female progeny with the dominant
allele
b. all male progeny with the recessive
allele
c. all male progeny with the dominant
allele
d. all progeny with the dominant allele
e. 50% male progeny with dominant
allele, 50% with recessive
f. 50% female progeny with dominant
allele, 50% with recessive
Part II: [20 points] Consider a cell with 1n = 2; one large
submetacentric chromosome & one small acrocentric one. Using
the back of the last page, diagram, being sure to demonstrate both the
differences and similarities between the two processes, and briefly
explain (in words) the significance of the difference(s). Also,
be sure to include in your diagram and/or explanation all the major
events of mitosis and meiosis, not just what the chromosomes are doing.
a. mitosis
b. meiosis
III. [40 points] Answer each question completely and clearly. 10
points each
1. Solve the following mapping problems (#1 & 2). Your final
answers should include the genotypes and phenotypes of both parents,
with the genes arranged in the correct order and in the correct allelic
configuration (i.e. dominant and recessive alleles arranged properly on
each chromosome). Map distances and interference must also
be calculated. Please place the completed answer in one spot so
that all of the components can be easily found.
+ + + 20
+ + d 23
+ b +
2
a + + 430
a + d
3
a b + 37
a b d 45
+ b d 440
2.
♀ ♂
r q g
57
r q +
1
r + g
389
r + +
27
+ + +
1010 32
+ q +
4 52
+ q g
40
+ + g
2
3. A geneticist's preliminary results, and the results of a second,
larger study are shown below. In both cases, known doubly
heterozygous organisms were test crossed. Analyze each experiment
separately, and then draw a conclusion about the MOST LIKELY map of the
two genes tested. If the conclusions differ, explain which
you think is correct, and why you think it is more likely to be valid.
A B
QR 22 220
Qr 30 300
qr 22 220
qR 26 260
4. When people from Earth landed on the first planet on which
they found something recognizable as eukaryotic life, they determined
that reproduction appeared to be similar to what we see on Earth, that
is, meiosis and fertilization similar to what we have been
studying. In an effort to map some genes which had been studied
sufficiently to be sure of a genotype- phenotype relationship, complete
dominance, and “Mendelian inheritance”, the following testcrosses were
done (tester parent is listed second), and progeny counted. Map
the genes. Determine the genotypes of the original mating
pair. Write the answer all together in one place so that it can
be found easily. Show your work.
red ears, orange noses x purple ears, pink noses
red ears, orange noses 46
red ears, pink noses 7
purple ears, orange noses 5
purple ears, pink noses 42
red ears, four fingers x purple ears, six fingers
red ears, four fingers 5
red ears, six fingers 47
purple ears, four fingers 45
purple ears, six fingers 3
four fingers, orange noses x six fingers, pink noses
four fingers, orange noses 12
four fingers, pink noses 40
six fingers, orange noses 41
six fingers, pink noses 7
bonus: Write a question that you studied for, and forgetful me, I
neglected to ask. Answer your question. PLEASE ask yourself
something you can answer well! PLEASE answer the question you
actually ask. [up to 5 points awarded based on question &
answer]
npx =
n! * [p^x][q(^n-x)]
x!(n-x)!