Dr. Reichler’s Bio 301M   MWF 9-10am    Print Name:____________KEY_______________
Exam #1   February 13, 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. Why is using disproof more certain than looking for proof? (8 pts)
Positive proof can be misleading as positive data does not always mean something is true.  Additionally, using positive proof can lead us to favor a single hypothesis.  Disproof is more certain because once something is shown to be false, it is always false.  Plus using disproof leads us to look for multiple hypotheses thereby not getting stuck on one.

2. Using rules 1 and 2 of Strong Inference, the parts prior to doing an experiment, answer the following question:  What is the function of the non-coding part of human DNA? (8 pts)
Create multiple hypotheses:  Non-coding DNA controls gene expression.  Non-coding DNA is used as an energy source.  Non-coding DNA has no information at all.  Design an experiment or experiments to disprove the hypotheses:  Eliminate the non-coding DNA and check if cell what functions are lost.

3. If nine nucleotides are deleted in the coding region of a gene, what will be the effect on the protein produced? (8 pts)
Three amino acids will be missing, the rest of the sequence will be normal.

4. Is a cell with 11 chromosomes haploid or diploid?  How do you know? (4 pts)
Haploid.  Diploid chromosomes come in pairs, which would mean an even number of chromosomes.

5. Relate two of the five definitions of genes that we discussed in class to each other.  Do not simply list the definitions, but describe how they can be related together. (8 pts)
Any of:  Genes code for proteins that when they malfunction can cause diseases.  Genes code for proteins that lead to heritable traits.  When genes are replicated that leads to heritable traits.  Genetic diseases can be inherited and/or replicated.  Genes code for proteins that control development.

6. Would a species that reproduces sexually or asexually have an advantage in an environment that is not changing?  Why? (4 pts)
Asexual reproduction would be favored because it can produce more offspring, and this constant environment does not require much genetic diversity.  OR  What works now will work later so diversity might be bad while consistency is good.

7. If the trait for liking chocolate is controlled by a single gene with two alleles (L= likes chocolate; H= hates chocolate) and two parents who like chocolate have a child who hates chocolate, which allele is dominant, and what are the genotypes of the parents?  (Show your work for partial credit.) (8 pts)
Hating chocolate is recessive.  Both parents are heterozygous.

8. Female A has a mutation in her mitochondrial DNA.  In the third generation, which individuals will inherit this mutation?  Explain. (8 pts)
1                        Female A
2        Male B                                Female C
                  /\                                       /\
3   Male D    Female E        Male F        Female G

Male F and Female G.  MtDNA is inherited only through the mother, Female C.

9. A single gene codes for baldness with two alleles (B= dominant not bald; b= recessive bald).  Two parents who are not bald have 100 children, 50 girls and 50 boys.  None of the daughters are bald while half of the sons are bald.  How is this possible?  What are the genotypes of the parents?  (Show your work for partial credit.) (8 pts)
The baldness gene is on the X chromosome (sex-linked).  XB Y and XB Xb.
note:  Many students answered Bb x Bb.  This will yield 25% bald children, but no difference in the chance of baldness in boys or girls.

10. What effect would there be on evolution if DNA replication made no errors? (8 pts)
The number of individuals with a certain trait could change, but no new traits (genes or alleles) would be introduced.

11. How can one quantify the most evolutionarily successful individuals in a population? (4 pts)
The individual who passes on the most genes OR who reproduces the most.

12. One group of scientists publishes a paper showing that two populations of rabbits can produce fertile offspring and are therefore the same species.  Another group subsequently publishes a paper showing that the two populations of rabbits are not the same species.  The data of the first group is correct.  What data did the second group present? (8 pts)
That in nature the two populations of rabbits do not reproduce.

13. If someone is studying a population of wild pigs, and they notice that there has been a decrease in genetic diversity, what are two explanations for the population’s decrease in genetic diversity? (8 pts)
A bottleneck occurred or stabilizing selection occurred.  (Directional selection can also sometimes lead to decreased genetic diversity.)

14. Are humans evolving?  Why or why not? (8 pts)
Yes.  We have genetic diversity, and not everyone can reproduce.  6/8 for No, we do have genetic diversity, but there is little limit on reproduction.

Bonus:  Humans and chimpanzees share about 98% of our DNA.  Would you expect to find the differences in coding regions or non-coding regions of the DNA?  Why? (3 pts)
Non-coding regions.  Coding regions code for proteins, etc and changes will likely lead to problems.  Changes in non-coding DNA would not have a direct effect on the organism.