Dr. Reichler’s Bio 325   TTh 9:30-11am    Print Name:______KEY______________
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 linked? (6pts)
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 credit.) (6pts)
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.
Difference-
OoA- H. sapien origin in Africa, common ancestor ~100k years ago, H. erectus replaced by H. sapien in non-African areas
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 people? (6pts)
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?  Why? (8pts)
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 not? (8pts)
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.