Genetics Test 3, Fall 2012
Name:
This test consists of two parts . In Part One, answer 5 of the 6 questions (15 points
each). In Part Two, all students must answer the entire question (25 points). Please
show all of your work, or you will receive no partial credit for incomplete answers.
Part One. Short Answers. Answer 5 of the following 6 questions. Please indicate
which questions you want me to grade. (15 points each).
Question One. A population (n=300) in Hardy-Weinberg equilibrium contains 70% of a
dominant phenotype and 30% of a recessive phenotype. Another nearby population
(n=180) has an 80% dominant phenotype to 20% recessive phenotype ratio. If 20
individuals from the first population migrate to the second population, what will the allele
frequencies in the conglomerate population be?
We did not do this this year…but you should be able to give, in general, what you
expect the impact on the allele frequencies to be (does the dominant allele frequency go
up or down, for example?)
Question 2. In mice, the autosomal locus coding for the beta-subunit of hemoglobin is 1
m.u. away from the albino locus (they are linked genes). Assume for a moment that the
same is true for humans. Normal skin pigment (A) is dominant to albinism (a) and
normal hemoglobin (H) is dominant to sickle cell (h). Since both of these traits are very
rare, assume that unaffected parents in the problem below are not carriers.
A. A son is born to an albino man with normal hemoglobin and a woman with normal
pigmentation and sickle cell anemia. What kinds of gametes will the son form, and
in what proportions?
Question 3. In the tubular flowers of Foxgloves, wild-type coloration is red while a
mutation called white produces white flowers. Another mutation, called peloria, causes
the flowers at the apex of the stem to be huge. Yet another mutation, called dwarf,
affects stem length. You cross a true-breeding white-flowered, normal-sized flowers,
tall plant by a true-breeding red-flowered, peloria, dwarf plant. All of the F1 plants are
tall with white, normal sized flowers. You then test-cross the F1 plants to red, dwarf,
peloria plants, and get 543 progeny of the types shown:
Red, dwarf, peloria.
White, tall, normal.
White, dwarf, peloria.
Red, tall, normal.
White, dwarf, normal.
Red, tall, peloria.
Red, dwarf, normal.
White, tall, peloria.
172
162
56
48
51
43
6
5
A. Which alleles are dominant?
B. What were the original genotypes of the parents in the original cross?
C. Draw a gene map showing all genetic distances
Question 4. If the mutation rate for a particular gene is 10-5, the number of individuals
in a population is 7000, and the frequency of the dominant allele in the population is 0.7,
how many generations of mutation will it take before the frequency of the dominant
allele is reduced to 0.5?
We did not do this this year…so ignore.
Question 5. A population of Yaks has the following proportions:
BB (Black).
Bb (Gray).
Bb (White).
543
254
335
Use Chi square analysis to determine if this population is in Hardy-Weinberg
equilibrium.
Question 6. Based on the data below, draw a phylogenetic tree using UPGMA
analysis.
Species A
Species B
Species C
Species D
Species E
Species A
Species B
Species C
Species D
1.4
1.7
3.3
2.7
0.6
3.5
2.5
3.7
2.8
0.4
Part Two: All students must answer the questions on the next two pages (25
points)
Your lab partner is designing an experiment in which they plan to amplify the ADE1
gene via PCR, then sequence the gene. They have asked you to critique each portion
of their experimental design below. The relevant portion of the ADE1 coding sequence
is shown.
5' CATCGTGCGC
CGGCACAGTG
AGTTACCCGA
CACGATGAGA
GGTTACATTA
CATGGCCTGG
GCCGATGTTC
ATATATCACC
GGGCTCTGCC
CTCTACCTGC
ACTCCGTCTA
GCACAGGCTG
TGGAAGGAGT
CGGGCTGCGT
CCAAAGCGGA
CAGACCTAAT
ACCAGGAGCG
GAGTCTGAGG
GCAGGGTGCG
TGGGCAGGAG 3'
1. Assuming that you want to copy the entire gene above, the forward primer will be
CATCGTGCGCGGTTACATTA. Is this correct? If not, give the correct sequence.
2. The reverse primer will be. GAGGACGGGTTAATCCAGAC. Is this correct? If not,
give the correct sequence.
3. Generally, forward and reverse primers should have Tm's within 5 degrees of each
other. Does this appear to be a good primer pair?
4. You lab partner claims that the length of the resulting PCR fragment will be 160 base
pairs. Is this correct? If not, give the correct length.
5. Your lab partner decides to use the forward primer to sequence their DNA using
Sanger sequencing. They claim that the first 5 bases of the resulting 200 base par
sequence will be GGGCTC. Is the sequence and/or the predicted length correct? If
either is incorrect, correct it.
6. Finally, your lab partner does not really understand how sequencing works, because
they have never really understood DNA replication. Explain to them how the
addition of an incoming base to the 3' end of the growing DNA molecule is critical to
both Sanger and Ion Torrent sequencing.