AGR 3303 - Genetics 13 Nov 2000

University of Florida - Fort Lauderdale

Exam #2: MOLECULAR GENETICS

Multiple choice (54 pts., 3 pts each)

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 and turn in this exam. Make sure your circle is unambiguous. Take time to relax. (Suggestion: put the problem into gene symbols, if that helps you to visualize the problem and its solution.)

1. What can you say about an organism with the following base composition?
   
   
A (adenine)= 18%      T (thymine)= 31%     G (guanine)= 31%      C (cytosine)=20%


1. Its genetic material is probably double-stranded RNA
2. This organism must have single-stranded DNA
3. This organism must have double-stranded DNA
4. This organism has collinearity between the pyrimidines and the purines
5. This is mitochondrial DNA
   
   
2. If an experiment had used radioactively labeled human insulin DNA, in a microbial synthesis, what would you expect to find in the insulin protein produced (think carefully about this):
   
1. radioactive P would occur in the insulin
2. both radioactive P and S would occur in the insulin
3. radioactive S would occur in the insulin
4. neither radioactive P or S would occur in the insulin
5. insulin would not be produced
   
   
3. Frameshift mutations are observed because:
   
1. The DNA code is commaless
2. The DNA code has stop codons
3. The DNA code is antiparallel
4. The DNA code is degenerate
5. The DNA code is ambiguous
   
   
4. Human insulin can be produced by bacteria, using human DNA, which proves:
   
1. DNA is a double helix
2. human DNA is a transforming principal
3. the DNA contains S, not P
4. there is base pair complementarity
5. bacteria are endosymbionts of people
   
   
5. Which statement is true of the double helix?
   
1. T pairs involve two hydrogen bonds
2. purine pairs with purine
3. heating causes the strands to anneal
4. G pairs with T
5. U pairs with T
   
   
6. Where would you expect to find the genetic information describing the potential characteristics of Tyrannosaurus rex?
   
1. In virtually every cell of its body.
2. Depends on the characteristic; eye color genes would be found in its eyes, hemoglobin genes in its erythrocytes.
3. In the ribosomes.
4. Only in its germ cells, i.e., primary spermatocytes or oocytes.
5. In a place in New Mexico called Roswell.
   
   
7. Parent plants with the genotypes AABBCC and aabbcc were crossed, and their F1 progeny were backcrossed to a homozygous recessive tester. The 1000 backcross progeny had the phenotypic distribution:
   
Phenotype ABC abc AbC aBc Abc aBC ABc abCNumber 355 355 5 5 95 95 45 45What is the map distance between A and C?

1. 1 map unit
2. 10 map units
3. 20 map units
4. 30 map units
5. 40 map units
   
   
8. Which sentence describes the general relationship between the sequences of a polypeptide and its respective mRNA?
   
1. The number of amino acids in the polypeptide is three times the number of nucleotide pairs.
2. The number of bases in mRNA is three times the number of amino acids.
3. The presence of wobble makes it impossible to predict a numerical relationship between the units in a polypeptide and its respective mRNA.
4. The number of amino acids in mRNA is three times the number of bases in the polypeptide.
5. The code is ambiguous, which makes it impossible to predict a numerical relationship between a polypeptide and its respective mRNA.
   
   
9. A single piece of single-stranded DNA reads 5' CGGCATTAC 3'. Which of the following pieces of single-stranded DNA could form a normal, complimentary double helix with the original piece?
   
1. 5' GTAATCGGC 3'
2. 5' GTAATGCCG 3'
3. 5' CGGCTAATG 3'
4. 5' GCCGTAATG 3'
5. 5' GTATACGGC 3'
   
   
10. Watson and Crick (1953) proposed:
    
1. the genetic code
2. that DNA is the hereditary molecule
3. the Central Dogma
4. the structure of DNA
5. genetic engineering
   
   
11. What has molecular biology added to the knowledge of genetics
    
1. proof of the inheritance of acquired characteristics
2. proof that genes act as particles
3. proof that genes are made of chemicals
4. proof that genes are located in the chromosomes
5. proof that both the female and the male parent contribute to the characteristics of the offspring
   
   
12. The bacteria of Avery et al. (1944) were transformed by a substance which was inactivated by:
    
1. ³²P
2. ³⁵S
3. polymerase
4. RNase
5. DNase
   
   
13. In the lac operon,
1. lactose binds with the DNA, preventing transcription
2. lactose binds with a protein, preventing translation
3. a protein binds with the DNA, preventing transcription
4. there are three regulatory genes and one structural gene
5. translation results in lactose
   
   
14. Which of the following is a nucleotide of DNA:
    
1. deoxyribose + uracil + phosphate group
2. deoxyribose + thymine + phosphate group
3. deoxyribose + nitrogenous base
4. ribose + pyrimidine + phosphate group
5. ribose + ATP
   
   
15. What molecule is transcribed from the DNA template, is single stranded, is typically a large molecule, and has a short half-life (high turnover)?
    
1. ribosome
2. mRNA
3. rRNA
4. enzyme
5. polypeptide
   
   
16. Based on the Watson-Crick model of the double helix:
    
1. if you know the content of one nitrogenous base (e.g, A) then you know the content of the other three (e.g., T, G, and C)
2. nitrogenous bases of antiparallel strands are paired by hydrogen bonds
3. the structure explains the function
4. for every purine there must be a pyrimidine
5. all of the above
   
   
17. Among this group, who proved that DNA is the genetic material?
    
1. Avery, MacLeod, and McCarty - transforming principle
2. Darwin - evolution by natural selection
3. Mendel - unit factors of inheritance
4. Watson and Crick - double helix
5. McClintock -jumping genes
   
   
18. The normal human metabolic pathway makes substance Z from substance X, as shown below.
    If both Enzyme A and B were functional, what would be the most probable consequence.
    
    

    	Enzyme A		Enzyme B
    A	>----->	B	>----->	C

1. Substance Y would accumulate in the body
2. Substance X would accumulate in the body
3. Enzyme B would accumulate in the body
4. Enzyme A would not be produced
5. Enzyme B would go ahead and complete the synthesis of Z

Fill in the blank (21 pts., 1 pt. each).

In each of the following twenty-one blank spaces, insert the correct word or phrase.

19. The form of the DNA molecule, as proposed by Watson and Crick

__________________________________.

20. The three-nucleotide "word" in mRNA, which specifies a single amino acid

__________________________________.

21. An oligomeric protein which is important in the blood.

__________________________________.

22.A method for artificially replicating short sequences of DNA segments to large number of copies

__________________________________.

23.A type of mutation involving a deletion or an insertion of one or more nucleotides, resulting in a garbled message

__________________________________.

24. "Wobble" in the third nucleotide of tRNA's anticodon is believed to result in inexact complementarity. This permits what key characteristic of the genetic code?

__________________________________.

25. The correspondence between the sequence of nucleotides and the sequence of amino acids resulting from translation

__________________________________.

26.A cutter enzyme

__________________________________.

27. The place in a protein where structural integrity is required for function; mutations which disrupt the protein here usually result in defective protein

__________________________________.

28. An organelle which is believed to have been an ancient cellular invader; a possible endosymbiont

__________________________________.

29. The regulatory gene which binds with a repressor protein, preventing RNA polymerase from binding with the promoter, thus preventing transcription

__________________________________.

30.A nitrogenous base present in RNA, but not in DNA (spell it out)

__________________________________.

31. Virus which attacks bacteria; often used in genetic studies

__________________________________.

32. An organism lacking a nucleus

__________________________________.

33.A process of sudden genetic change, the source of most alleles

__________________________________.

34. When two enzymes contribute to a metabolic pathway, Mendelian 9:3:3:1 phenotypic ratios are sometimes altered; the genetic phenomenon is:

__________________________________.

35. The level of protein structure that involves the actual sequence of amino acids

__________________________________.

36. A type of organism in which transcription and translation are separated in space:

__________________________________.

37. The kind of evidence for DNA as the genetic material that is provided by the UV action spectrum:

__________________________________.

38. The number of possible codons:

__________________________________.

39. A ribonucleoprotein organelle that is the site of translation of mRNA codons into amino acids.

__________________________________.

Short answer (25 pts, 5 pts each)

Attach extra pages as necessary

40. Describe in chemical terms how a mutation can affect the phenotype. Make sure to say what a mutation is and mention factors and mechanisms that will lead to a trait being expressed or not expressed.

41. How can knowing the genetic code be applied to inherited diseases? What are some obvious ethical issues involving this information?

42. Explain the simple idea behind the expression, "one-gene, one-enzyme," which connects Mendelism with molecular genetics. And how may the expression "one-gene, one-enzyme" be incomplete?

43. Why are microorganisms so useful in molecular genetic experiments? In what situations may microorganisms be inadequate or inappropriate for genetic studies.

44. Give some examples of the basic laboratory procedures used in studying DNA and describe their purpose or function.