Multiple choice (60 pts.)

Please read these carefully. One and only one response (a, b, c, d, or e) completely and correctly answers the question, or completes the statement. Circle the appropriate response. Make sure your circle is unambiguous.

1. RNA polymerase is active in:
1. a. translation
2. b. replication
3. c. Barr bodies
4. d. all of the above
5. e. none of the above

2. A gene can be defined as:
1. a a chromosome
2. b a unit particle of inheritance
3. c a form of an allele
4. d all of the above
5. e none of the above

3. With probably 2,000 to 3,000 manatees left in Florida, UF-IFAS conservation geneticist Brian Bowen says that DNA fingerprints reveal dangerously low genetic diversity. While the genetic bottleneck is not as critical as the Florida panther, the survival of the manatee is vulnerable to a population crash, because of:
1. the likelihood of genetic drift
2. the danger of mutation
3. migration
4. all of the above
5. none of the above

4. 4. There are no systems currently available for cloning RNA. To prepare probes for detection of plant viruses whose genome consists of RNA, phytopathologists resort to synthesizing and cloning DNA copies from viral RNA. Indicate which one of the following enzymes can be used to synthesize DNA copies from RNA templates.
1. DNA polymerase I
2. reverse transcriptase
3. S1 nuclease
4. all of the above
5. none of the above

5. Assume that a single gene has three alleles. In a diploid organism, how many possible genotypes are there?
1. 2
2. 3
3. 4
4. 5
5. 6

6. Actual letter to Dear Abby (June 11, 1996): Recently a child in my husband's family was to undergo surgery. The child's mother asked all of the family members to donate blood. This child has A positive blood, and everyone in my husband's family except him also has A positive blood. My husband's blood type is O positive. I am convinced that the people he knows as his parents are not his biological parents. Do you think that the people he believes are his parents actually are? Or do you feel that he should confront them and ask for a DNA test? - Nameless in Arizona. Responding to Dear Nameless, Amy provided the following accurate advice:
1. Yes, confront them. It's right thing. Clear the air. There's no way two parents with blood type A could have a child with blood type O. In fact, first tell your mother-in-law, then ask her to read Klug and Cummings if she hasn't already.
2. No, let sleeping dogs lie. He obviously can't be their son, but they love one another so what does it matter?
3. Two parents with A positive blood can have a child with O positive blood. Stop stirring the pot.
4. Most likely your husband has the Bombay phenotype, a common mutation in the metabolic pathway of human isoagglutinogen proteins.
5. Your husband is hemizygous for the O allele because of sex linkage.

7. Following some experiments, Jack left 10 sunflowers growing in his garden. One was homozygous recessive for the allele for tall, thus its genotype was tt Nine were homozygous dominant, having the normal allele, thus their genotypes were TT. Assume that sunflower is a cross-fertilizing species and that the descendants of this group outcross and grow in the garden for several generations. When Hardy-Weinberg equilibrium occurs, what is the frequency of heterozygotes as a percentage of the population?
1. 1
2. 9
3. 18
4. 81
5. 100

8. The role of mutations in evolution is that they:
1. are the source of all genetic diversity
2. can drastically change gene frequencies
3. explain acquired characteristics
4. all of the above
5. none of the above

9. What is true about cancer:
1. cancer involves unregulated cell growth
2. probably all cancer has a genetic cause
3. cancer may involve mutations in regulatory genes
4. all of the above
5. none of the above

10. The lac operon is inducible by the presence of the metabolite lactose. It functions to:
1. allow structural genes to be turned on in the absence of lactose
2. allow structural genes to be replicated in the absence of lactose
3. translate from the messenger RNA when lactose is present
4. transcribe from the DNA when lactose is present
5. turn of the genes when glucose is present

11. The concept of metabolic pathways is important because it explains:
1. regulation of gene action
2. mutation
3. epistasis
4. cancer
5. population genetics

12. The basic unit of double-stranded DNA is a(n):
1. a. amino acid
2. b. nitrogenous base
3. c. nucleotide
4. d. ribosome
5. e. nucleosome

13. In replication, each double-stranded daughter DNA is composed of one strand which is old and one which is newly synthesized, thus replication:
1. a. is bidirectional
2. b. is collinear
3. c. is semiconservative
4. d. has fidelity
5. e. involves complementarity

14. The bacteria of Avery et al. (1944) were transformed by a substance which remained active:
1. a after spontaneous creation
2. b when radioactive 32P was detected
3. c after treatment by RNase
4. d after treatment by DNase
5. e all of the above

15. Enzymes:
1. do not occur in the nucleus
2. reduce the activation energy
3. are produced in viruses (phages)
4. occur in the nucleus, not the cytoplasm
5. are small, diffusible molecules

16. Direct proof for evolution comes from:
1. taxonomic comparison of modern organisms
2. the fossil record
3. determination that some traits are advanced, others primitive
4. there's no other way to explain life
5. there can be no proof, because evolution is only a theory

17. Long-term immunity to infectious diseases can be obtained by vaccination, due to:
1. genetic diversity in the immune system
2. secondary immune response
3. B memory cells
4. all of the above
5. none of the above

18. Human immunodeficiency virus (HIV) which causes AIDS is so difficult to treat because:
1. the virus attacks the T4 cells which are part of the immune system
2. the virus mutates rapidly
3. a vaccine does not exist
4. all of the above
5. none of the above

19. In Great Britain, the shift in coloration of the peppered moth, from a dark melanic form to a light, speckled form, was due to:
    1. evolution by natural selection
    2. air quality laws in the 1960s
    3. survival of the fittest
    4. all of the above
    5. none of the above

20. The human genetic disease phenylketonuria (PKU) results in mental retardation. The mental retardation effect can be diminished by restricting the amount of phenylalanine in the diet. PKU is an example of:
    1. a toxic byproduct of blocked metabolic pathway
    2. a defective enzyme
    3. a genetic abnormality
    4. a disease whose severity involves the interaction of a gene and the environment
    5. all of the above

21. Fill in the blanks (14 pts.) You only need to fill in one of each of seven numbers (1 to 7); any subsequent fill-ins of the same number will be ignored.

    The Genetic Code

The genetic code is the chemical dictionary for making 1____________________s, which are chains of 2____________________s; they vary depending on their sequence. Most living things have genes made of DNA, a chain of 3____________________s. The particular DNA sequence in each gene tells what kind of 1____________________ to make. There are two steps in this so-called central dogma. The DNA first serves as a template for enzymes to 4____________________ (a verb) its sequence onto an intermediate molecule, messenger RNA (mRNA) which is then translated into 1____________________ using a coding dictionary. The decoding is done by a class of adapter molecules, 5____________________. To decode mRNA, each kind of 5____________________ has a particular 2____________________ attached to one end. At the other end, the 5____________________ has a region, the anticodon, which recognizes the 3____________________s in the mRNA codon. Only a 5____________________ with the matching anticodon can insert an 2____________________ into place along the lengthening 1____________________. The translation occurs in small organelles called the 6____________________ simultaneous with the reading of the mRNA codons by the 5____________________. In this way there is strict correspondence or collinearity between the 2____________________ sequence in the 1____________________ and the 3____________________ sequence in the mRNA. To make 1____________________ there must be codons for each of 20 necessary 2____________________s but the "letters" of the mRNA message consist of only four kinds of 3____________________. Therefore, the 3____________________ s must be read in sets of three, which provides 4 X 4 X 4 = 64 possible triplet "words," or codons in the mRNA. The 64 codons are more than enough combinations to spell out 20 2____________________s. How does the 5____________________ anticodon recognize the codon? The anticodon region of 5____________________ is itself a triplet of 3____________________s. The three anticodon 3____________________s must hydrogen-bond with the complementary 3____________________ of the codon (cytosine with the guanine, uracil with adenine, since this is mRNA). There are as many kinds of 5____________________ as there are kinds of 2____________________. Some 5____________________ s can recognize more than one codon, because the third 3____________________ in the anticodon may wobble; it doesn't have to complement the codon exactly. Consequently, some of the 64 codons in the genetic dictionary are synonyms, specifying the same 2____________________; the code is thus redundant or degenerate. A codon can indicate no more than one 2____________________; the code is unambiguous. Some codons specify punctuation signals such as "start" or "stop." These tell the protein-making machinery to start or stop making 1____________________. A 3____________________ substitution in the middle of a gene can spell an inappropriate stop signal, resulting in no 1____________________ produced. This is a nonsense mutation. The genetic code has no spaces or commas between words; it must be read in exact, registered sequence. If the reading frame shifts by the loss or addition of a single 3____________________, then all succeeding codons are translated wrong. This is an example of a 7____________________ mutation. Scientists cracked the genetic code by finding out which 2____________________s were produced from synthetic mRNA sequences. The code is almost the same in all organisms; it is universal. (The few exceptions are interesting.) Biotechnologists have used the genetic machinery of bacteria to produce insulin protein, based on human insulin DNA as a template. Is the new insulin protein human?

Essay

22. It is predicted that before the end of 1998 the Sanger Centre will complete the sequencing of the genome of C. elegans, a worm. Briefly explain what is a sequence, what is a genome, and how this knowledge may be useful in human health. (10 pts.)

23. What is the current status of genetic knowledge applied to each of the following areas? (16 pts.)

Topic	Status (i.e., "it's here" (with an example) or "coming" or "not in sight")	Challenges (knowledge needed, etc.; if a technology is already here, there may still be challenges, including pitfalls)
Stop aging
Prevent breast cancer
Design your offspring
Improve the nutritive value of food
Develop a vaccine against HIV/AIDS
Predict the likelihood of disease
Sequence the human genome
Transgenic insect resistance in crops

24. Information (e.g., computers, libraries, tools, and cultural inventions) is sometimes used as a metaphor for genetics. Develop this metaphor and criticize it. Is it useful? Does it lead to misunderstanding? Is another metaphor, e.g., the ecosystem, sometimes more appropriate? In this short essay, make sure that you discuss the four primary characteristics of the genetic material, and the most fundamental terms useful in genetics and the world at large (e.g., gene, genome, environment, problem solving, evolution, adaptation.) (20 pts.)