Download NAME EXAM # 1) (15 points) Next to each item in the left

NAME
1)
\<\ recessive
coefficient of coincidence
\\ test cross
multiplication rule
sister chromatids
locus
penetrance
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chromomere
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polar bodies
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epistatic allele
3
KEy
(15 points) Next to each item in the left-hand column place the number from the right-hand column
that k t corresponds:
autosome
6
EXAM #
hernizygous
\\g synapsis
1) specialized microtubules present at spindle poles
2) degree to which phenotype altered
3) Z in females
4) w+
5) encodes temperature-sensitive enzyme
6) not a sex chromosome
7) localized condensation
8) does not apply for events that are not mutually exclusive
9) these undergo crossing over at pachytene
10) W in males
11) cross to homozygote for recessive allele(s)
12) kind of grasshopper
13) joined at centromere
14) degenerate
15) fraction of double crossovers expected that actually occur
16) central element forms
17) probability of each order of s objects of one type and t objects ofanother type (s+t=n)
18) autonomously replicating chromosome
19) Ki'
20) loss of synaptinemal complex
21) probability of 2 chromosomes undergoing nondisjunction together
22) map location
23) can be used only for independent events.
24) chromosome lacking a centromere
25) lacks androgen receptor
26) cross to determine if two genes involved
27) proportion of carriers that are affected
28) TDF
29) gene encodes enzyme that functions upstream in pathway
30) number of ways of ordering s objects of one type and t objects of
another type (s+t=n)
EXAM #
NAME
2) a) (2 points) In a self cross of an AaBbCc plant (where these three genes assort independently), what
is the expected frequency of A-B-cc progeny?
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b) In many organisms, including ourselves, the sex chromosomes share a%omologous region within
which crossing over occurs, but also have regions unique to the X and Y.
i. (2 points) What pattern of inheritance would genes in the shared region show? Would such genes
show typical sex-linked or autosomal modes of inheritance, or would they show some other pattern?
ii. (2 points) How could genes located in the shared region be identified in crosses?
c) (3 points) The following results are tested for agreement with a 3: 1 expectation by the 2 test:
For each test, calculate the 2 statistic.
Which test will give the lower P value?
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EXAM #
NAME
3) (10 points) A geneticist obtains two pwe-breeding strains of Petunia. One has red flowers and the
other has white flowers. When these are crossed to one another, the Flplants are all red flowered.
When these Flplants are self crossed, the F2consists of red, pink, and white flowered
in the
ratio 13 red: 2 pink: 1 white. Explain these observations using gene symbols of your own choice.
Show genotypes for all phenotypic classes in the P, F,, and F2generations.
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NAME
EXAM #
4) (8 points) As described in class, the yellow mutation in the mouse (designated J) causes yellow coat
coloration when heterozygous, but is lethal when homozygous. A second, independently assorting,
allele (e) causes the ears to be absent when homozygous. A yellow mouse with normal ears is crossed
to a grey mouse that is earless. Yellow progeny with normal ears were selected and crossed to one
another. Assuming both genes are autosomal, what are the expected progeny types? In what ratio are
they expected to occur?
NAME
EXAM #
5) The normal color of Delphinium flowers is blue. Three pure-breeding lines having white, pink, or
purple flowers are obtained. When plants from the white strain are crossed to plants from the pink
strain, the F, progeny are blue flowered. When these F, plants are crossed with one another, an F, is
produced that consists of 9 blue: 3 pink: 4 white. When plants from the pink strain are crossed to
plants from the purple strain, the F, progeny are also blue flowered. When these Fl plants are crossed
with one another, an F, is produced that consists of 9 blue: 3 purple: 4 pink.
a. (6 points) Explain these results using gene symbols of you own choice.
b. (3 points) Draw a biochemical pathway for flower pigment synthesis consistent with the cross
results. Indicate which genes encode the enzymes that catalyze each step in the pathway.
NAME
EXAM #
6) (6 points) The monohybrid cross Yy x Yy is made, and eight progeny are scored for whether they
show the phenotype of the dominant allele (i.e. are YJ or are homozygous for the recessive allele.
Calculate the probability of the single most likely outcome for these eight progeny (set up; but do not
bother computing answer).
NAME
EXAM #
7) (9 points) Draw schematically the appearance of a pair of telocentric homologs at pachytene, diplotene,
and anaphase I. Use wiggly lines to represent the chromatids of one homolog and smooth lines to
represent the chromatids from the other homolog. Assume two crossovers take place bekeen the two
homologs.
NAME
EXAM #
8) a. (3 points) As described in class, Calvin Bridges showed that the X chromosomes of Drosophila
undergo nondisjunction in about 1 in 2,000 meioses. Subsequently, it was shown that most X
chromosomes that undergo nondisjunction have failed to undergo crossing over. Based in your
knowledge of mei s' suggest an explanation for why chromosomes that do not cross o v e r J k p d y
fail to segregate. rom eir homologs in meiosis I.
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b. (3 points) In addition to the work described in class, Bridges crossed the WIWNmatroclinous
exceptions he recovered to w+N males. He found a very high frequency (about 5%)of matroclinous
females and patroclinous males in the progeny. Suggest an explanation for why X-chromosome
nondisjunction is so much higher in X X Y females than in XX females.
NAME
EXAM #
9) The following shows a pedigree for a very rare disease known to be caused by an autosomal recessive
allele.
a. (3 points) What is the probability that the first child of the couple at the bottom of the pedigree
(marked ?) will be affected by the disease? (Assume that no more than one individual from each set of
grandparents carries the recessive allele).
b. (3 points) Hold on! The sister of the mother in question just had an affected child, as indicated
below. Based on this new information, what is the probability that the child marked ? will be affected
by the disease?
c. (3 points) Sadly, the first child is affected. If the couple have 5 more children, what is the
probability that at least one of these five will be affected by the disease?
NAME
EXAM #
10)(7 points) As described in class, the light body mutation (0 in the moth is sex linked. Another
recessive mutation, gnarled bristles (gn) is known to be autosomal. A male from a pure-breeding light
body strain is crossed to a female from a pure-breeding gnarled bristle strain. The F, progeny are then
allowed to intermate to produce an F,. What phenotypes are expected in each sex in the F, and F,? In
what ratios are these phenotypes expected?
NAME
EXAM#
v6y
a) (2 points) Is mitotic anaphase most similar to anaphase I or anaphase II? Explain your answer.
Anaphase of mitosis is most similar to Anaphase 11, because in both cases the sister
chromatids are being pulled to the opposite poles, and there is no change in chromosome
number after anaphase or anaphase 11. In anaphase I, the homologs are separated from each
other (go to opposite poles) and the result is that the chromosome number is halved.
b) (2 points) How would anaphase of mitosis be affected if colchicine was added to the cells?
The cells would start mitosis, but not be able to proceed past prophase to metaphase, so
anaphase would not be observed.
c) (4 points) Diagram a cell in metaphase I1 from the lily anther and from the lily ovule. Note two
differences between the two drawings.
see attached
d) (4 points) Give a brief description of the experimental steps of our artificial selection experiment with
Brassica rupu.
1. Plant (approximately 100) seeds of "wild type" rapid-cycling Brassica rapa.
2. After two weeks, score each of the plants for trichome number.
3. Keep the 10 plants that have the most trichomes.
4. Cross-pollinate those 10 plants, and allow them to set seed.
5. Collect and plant seeds from the 10 plants.
6. Score trichome number on the plants that grow from the collected seed.