Dr. Reichler’s Bio 325 TTh 9:30-11am
Exam #3 December 7, 2006
Read each question carefully and don’t hesitate to
ask if a question seems unclear. If possible, answer each
question in the space provided, but if needed, continue on the
back. If you use a drawing as part of your answer, be sure to
also include a written explanation. These questions have specific
answers, although for some, more than one answer is possible. To
receive full credit you must clearly and fully answer the question
being asked. This exam is worth 103 points with the points for
each question noted in parentheses.
1. There are three Powerpuff Girls and each one has a different hair
color. If a single gene codes for hair color, how can this single
gene give rise to three phenotypes? (6pts)
Any one of: incomplete
dominance, codominance, more than two alleles, environmental effects
2. The Powerpuff Girls also have three different eye colors. What
evidence would indicate that the gene for hair color and eye color are
Recombination between these genes
will be less than 50%.
3. One gene controls voice tone in Powerpuff Girls with a shrill voice
being dominant and a normal voice being recessive. The
Powerpuff’s mom is heterozygous and their dad is homozygous
recessive. There is a new Powerpuff Girl on the way, what is the
chance that she will have a shrill voice? (Show your work for partial
S=dom, shrill; s=rec, normal.
Mom= Ss, Dad= ss. Offspring 50% SS, ss. So 50% chance of
having shrill voice.
4. A single sex-linked gene codes for Powerpuff Girl superpowers.
The superpower allele is dominant. Females imprint the dominant
allele and men do not imprint the dominant allele. Can a male
have Powerpuff superpowers? (Show your work for partial credit.) (8pts)
No, male gets X chromosme from mom,
and so the dominant allele will always be imprinted, methylated and
inactive, in males.
5. Could RFLP analysis determine if an individual was homozygous or
heterozygous for a particular gene? Why or why not? (6pts)
Yes, if the difference in the alleles
is in a sequence recognized by a restriction enzyme, then the two
alleles will give different sized bands after cutting and running on a
gel. The heterozygous will show both patterns, the homozygous
only one pattern.
6. If in the past some African men migrated to Asia and had offspring
with the Asian women, would you expect to see evidence of this in the
mitochondrial DNA? Why or why not? (6pts)
No, mtDNA is only inherited via
females, so the African males will not leave any evidence of their
presence in the mtDNA.
7. What is one similarity and one difference between the “Out of
Africa” and “Multiregional” hypotheses? (6pts)
Any one of:
Similar- both have H. erectus
originating in Africa and migrating to other regions.
OoA- H. sapien origin in Africa,
common ancestor ~100k years ago, H. erectus replaced by H. sapien in
MR- H. sapien origin in different
regions, common ancestor ~1million years ago, H. erectus evolved into
H. sapien is different regions
8. What role do nature and nurture play in our recognition of other
Nature- we have an inherent ability
to group people by coalition membership, with me or against me.
Nurture- how we define who is part of
our group is largely environmentally determined.
9. You are a llama breeder, and the best prices are for llamas with
long necks, orange color, or friendly dispositions. You have a
pair that is heterozygous for all three genes, and the traits you want
are all coded for by recessive alleles. What is the chance that
you will get a llama with at least one of these desirable traits? (Show
your work for partial credit.) (8pts)
For each gene when two heterozygous
individuals mate, the chance of homozygous recessive offspring is
25%. So 25%+ 25%+ 25%=75%
10. You do the crosses involving the genes in question #9, and the
results turn out differently from your predictions. Why? (6pts)
These genes are linked. The
genes are close enough on the same chromosome so that there is a less
than 50% chance of crossing-over taking place between them. OR
Genomic imprinting- dominant alleles may be imprinted and therefore not
expressed. 4/6 pts X-linked- the probability of the trait will
differ in males and females.
11. If a virus inserted its DNA into the constant region of your
antibody gene causing the gene to become non-functional, would the
interrupted gene be inherited as a dominant or recessive allele?
Recessive allele. Having one
correct version should allow production of normal antibodies. For
someone to lack the ability to produce antibodies, they would need to
versions of the disrupted gene a la a recessive allele.
12. You want to know why Powerpuff Girls can fly so high. You do
PCR using their genomic DNA with primers that match the sequence of
their myosin gene (an important component of muscles), You separate the
amplified DNA on a gel, and you see two slightly different sized
products. Why? (6pts)
There is a gene family and/or a
pseudogene that gets amplified by the same primers.
OR There are two different
alleles, and each one is a slightly different size.
OR The larger bands are the products
copied from the template where the taq copies more DNA than is desired.
13. Some people with SCIDS were treated by genetically modifying their
bone marrow using viruses. Will these people pass on the
corrected version of the gene to their offspring? (6pts)
No, the modification is in the bone
marrow, only DNA in gametes is inherited.
14. Using the plasmid we discussed in class, is it possible to get blue
bacteria colonies that are not antibiotic resistant? Why or why
No, both the lacZ gene, whose gene
product gives rise to blue colonies if given X-gal, and the antibiotic
resistance gene are on the same plasmid. It is both or none.
15. You are looking at the number of recombinant offspring between
three genes: E, D, and N. The number of recombinants between E
and D is 20%. The number of recombinants between D and N is
16%. The number of recombinants between E and N is 4%. (Show your
work for partial credit.)
a. What is the order of these genes? (4pts)
E N D
b. Is it possible that there are fewer nucleotides between N and D than
between E and N? Why or why not? (4pts)
Yes, thet may have recombination hot
spots and cold. Meaning that the linkage map and sequence
(physical) map do not concur.
Bonus: What evidence suggests that the effects of birth season on
exam scores do not occur during the first few weeks of fetal
development? (3 pts)
The correlation between birthday and
exam scores is different in males and females, but during the first few
weeks of development all human fetuses are developing as females.
So if the effect occurs during the first few weeks, it should be the
same in both sexes.