Part I: Choose the one BEST answer. Circle its letter. Read each question and all 5 choices carefully because more than one answer might seem correct at first glance. 1.5 points each  

1. DNA transcription results in the synthesis of
a. messenger RNA
b. ribosomal RNA
c. transfer RNA
d. a and b
e. all of the above

2. Each single gene has
a. a single allele
b. exactly two different alleles
c. exactly two different alleles in one individual organism
d. one or two different alleles in one individual organism
e. many alleles in one individual organism 

3. Autosomes are
a. genes present on the X chromosome
b. source of new alleles
c. chromosomes other than W, X, Y, or Z
d. two copies of one gene
e. chromosomes other than X or Y

4. When red kernel corn and white kernel corn are crossed, the F₁ is pink, and the F₂ has red, light red, pink, light pink, and white kerneled corn. This is an example of
a. epistasis
b. codominance: two alleles of one gene
c. partial dominance: two alleles of one gene
d. multiple gene activity without epistasis
e. Mendelian dominance and recessiveness

5. Male pattern baldness is an example of a
a. sex limited trait
b. sex influenced trait
c. sex linked trait
d. a and b
e. b and c 

6. A DNA molecule is made up of 20.62% guanine. How much cytosine will it contain?
a. 10.31%
b. 41.24%
c. 79.38%
d. 20.62%
e. not enough information given
f. none of the above 

7. Multiple alleles can only be studied in
a. mutations
b. populations
c. blood groups
d. inheritance
e. antigens 

8. A heterogametic female is represented by which of the following?
a. XY
b. ZW
c. XX
d. ZZ
e. a and b
f. b and c
g. none of the above

9. DNA is successful as genetic material because it can
a. specify replicas of itself which are produced with few errors
b. carry linear information of any complexity
c. mutate
d. all of the above
e. none of the above 

10. For DNA to form a protein it must (in order)
a. replicate, translate, transcribe
b. translate, replicate, transcribe
c. translate, transcribe, replicate
d. replicate, elongate, transcribe
e. none of the above 

11. A man with a rare recessive X-linked disease marries a woman who is phenotypically normal. If the woman is homozygous at that locus, what is the probability that their offspring will have the disease?
a. 0% because the disease is rare
b. 0% because the child will receive a dominant allele from the mother
c. 100% because the child would receive the trait from the father
d. 50%
e. 25%
f. 0% for boys; 50% for girls 

12. A female child of the parents described in #11 marries a normal man. The probability that they will have a child with the disease is:
a. 0% because the disease is rare
b. 0% because the child will receive a dominant allele from the father
c. 100% because the child would receive the trait from the mother
d. 50% for boys; 0% for girls
e. 25% for boys and girls, alike 

13. During DNA replication, nucleotides are added at the
a. 3' - OH
b. 5' - OH
c. C-2 of the sugar
d. C-2 of the nitrogenous base
e. N-1 of the nitrogenous base 

14. The only known Y chromosome gene(s) whose expression can be detected without biochemistry is/are
a. male pattern baldness
b. facial hair and ridged tragus
c. hairy pinna
d. receding hairline
e. Turner's syndrome 

15. The three steps of any polymerization process are
a. initiation, replication, termination
b. start codon, repetition, stop codon
c. replication, transcription, translation
d. initiation, elongation, termination
e. initiation, elongation, translation

16. When can nondisjunction occur?
a. metaphase I
b. telophase II
c. anaphase I
d. diplonema
e. pachynema

17. Epistasis is:
a. a metabolic reaction in which complex molecules are broken down
b. a condition in which two genes are located so close that no recombination occurs between them
c. the occasional separation of two genes on the same chromosome by a recombinational event
d. the expression of a heterozygous phenotype which is distinct from that of either parent
e. the expression of one gene being modified by another

18. Translation is the process in which:
a. DNA directs the production of DNA
b. DNA directs the production of RNA
c. RNA directs the production of DNA
d. RNA directs the production of RNA
e. RNA directs the production of protein

19. Klinefelter's syndrome and trisomy X are both examples of
a. an excess of Barr bodies
b. trisomy of the sex chromosomes
c. aneuploidy
d. a and b
e. b and c
f. all of the above

20. An RNA molecule is made up of 20.62% guanine. How much cytosine will it contain?
a. 10.31%
b. 41.24%
c. 79.38%
d. 20.62%
e. not enough information given
f. none of the above

21. A protein could be any of the following EXCEPT
a. an RNA
b. an enzyme
c. part of the structure of a cell
d. part of the structure of a chromosome
e. part of the structure of a membrane

Part II: Briefly describe the important similarities and differences between DNA and RNA. Draw a segment of a DNA molecule and a segment of an RNA molecule, at least 3 subunits long, each. Be sure that you show enough detail in the diagrams to support your explanation. [13 points] 

Part III: Short answer. 8 points each. Omit 2 - Answer 7. 

1. When blue and white flowers, of a previously unknown variety, are crossed they give rise to light blue flowers. 

a. What is a simple explanation for this observation?
b. How would you determine whether one or two genes is likely to be involved?   

2. Explain the difference between co-dominance and partial dominance. Give one example of each. If you were studying a new system which appeared to be expressing either co-dominance or partial dominance, how would you go about determining which explanation best fit your system? 

3. Demonstrate a pair of reciprocal crosses in which criss-cross inheritance is seen in one but not the other cross. Explain what can be inferred from this system: how can these observations be explained, and what do they teach us? 

4. a. Do all genes encode polypeptides? Explain. 

b. No gene encodes a lipid or a carbohydrate, yet there are genetic disorders which result in an abnormality or the absence of a particular lipid or carbohydrate in an individual with the mutation. Explain this apparent discrepancy or contradiction - how can this occur?  

5. Lethal alleles can be dominant (such as Huntington disease) or recessive (such as Tay Sachs). Demonstrate the inheritance pattern for each of these. How can a dominant lethal allele exist and persist in a population? How can a recessive lethal allele exist and persist in a population?

6. In the imaginary organism the beebop, two individuals expressing the recessive phenotype blue eyebrows (rather than the dominant phenotype of orange eyebrows) have offspring with orange eyebrows. Without invoking spontaneous mutations, explain this occurrence. 

# 7 - 9. For each of the following sets of observations (unrelated to each other): What is the most likely explanation for the observation: One gene or two? Describe a likely biochemical pathway consistent with the observation, and show which genotypes correspond to which phenotypes. Explain your logic (full credit requires an explanation as well as a pathway).  

7. Certain plants can be bred to produce no color, purple color, or red color. From a cross between two purple plants, the following progeny were obtained: 94 purple plants, 31 red plants, and 43 colorless plants.  

8. A 9 green : 6 blue : 1yellow ratio among the offspring of a cross between two green organisms.  

9. A 10 tall : 6 short ratio among the offspring of a cross between two tall organisms.  

10. In the guinea pig, one locus involved in coat color has (at least) 4 alleles which show a hierarchical dominance as follows: C (black) > c^k (sepia) >c^d(cream) >c^a (albino). For each of the following crosses of sepia x cream , write the parental genotypes and predict the phenotypic ratios among the progeny from the cross.

a. each guinea pig had an albino parent.
b. the sepia guinea pig had an albino parent and the cream guinea pig had two sepia parents
c. the sepia guinea pig had 2 black parents and the cream guinea pig had two sepia parents   

bonus: Write a question that you studied for, and forgetful me, I neglected to ask. Answer your question. PLEASE ask yourself something you can answer well! PLEASE answer the question you actually ask. [up to 5 points awarded based on question & answer]