MultipleChoice. There is onebest answerfor eachquestion. (30 pts total)
Correct answers are in bold print.
1. Which of the following mutations would be most likely to have a harmful effect on an organism?
A. a base-pair substitution
B. a deletion of three bases near the middle of the gene
C. a single base deletion near the middle of an intron
D. a single base insertion near the start of the transcribed region
2. Which component is not directly involved in the process of translation?
A. mRNA
B. DNA
C. tRNA
D. ribosomes
E. none of the above
3. Which of the following statements about RNA polymerase is correct?
A. It functions in translation
B. It transcribes both introns and exons
C. It starts transcribing at an AUG triplet on one DNA strand.
D. It is necessary for 5'-cap formation
4. The elongation of the leading strand during DNA synthesis
A. progresses away from the replication fork
B. occurs in the 3'Æ5' direction
C. produces Okazaki fragments
D. depends on the action of DNA polymerase
E. does not require a template strand
5. A paleontologist has recovered a bit of organic material from the 400 year-old skin of an extinct dodo. She would like to compare DNA from the sample with DNA from a living bird. Which of the following would be most useful for increasing the amount of DNA available for testing?
A. restriction fragment analysis
B. gel electrophoresis
C. polymerase chain reaction
D. radioactive probe analysis
E. RNA polymerase reaction
6. Your bone cells, muscle cells, and skin cells look different because
A. different kinds of genes are present in each kind of cell
B. they are present in different organs
C. different genes are expressed in each kind of cell
D. they contain different numbers of genes
E. different mutations have occurred in each kind of cell
7. Which of the following nucleotide sequences would code for the polypeptide sequence amino end: arginine-glycine-aspartate: carboxyl end
A. 5'-AGA GGA GAU-3'
B. 3'-AGA GGA GAU-5'
C. 5'-ACA CCC ACU-3'
D. 3'-GGG AAA UUU-5'
8. The presence of lactose results in high levels of transcription of the lactose operon by
A. blocking the binding of repressor protein to the operator site
B. destabilizing the DNA duplex
C. binding to the operator site
D. binding to and thus changing the shape of RNA polymerase
9.E. coli cells grown in 15N medium are transferred to 14N medium and allowed to grow for two generations (two cell replications). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
A. one high-density and one low-density band
B. one intermediate density band
C. one high-density and one intermediate-density band
D. one low-density and one intermediate-density band
10. The synthesis of an RNA molecule from a DNA template is known as
A. translation
B. transcription
C. replication
D. splicing
E. recombination
Short Answers (30 pts total)
1. You discover a previously undescribed reptile in the rain forests of Costa Rica. The animal's DNA has 15% adenine. (3 pts)
What percentage is thymine? 15%
What percentage is cytosine? 35%
What percentage is guanine? 35%
2. Consider the gene that encodes the hemoglobin protein. Arrange the following events in the most likely order in which they would occur. Write the correct order on the line provided at the end of the question. (6 pts)
A. An incorrect codon is created in the mRNA of the hemoglobin transcript.
B. The oxygen binding site of the hemoglobin protein is altered.
C. A mother (an X-ray technician) accidentally steps in front of an operating X-ray generator.
D. A base substitution mutation occurs in the DNA of the gene for hemoglobin.
E. A child dies.
F. The oxygen transport capacity of the body is severely impaired.
G. The tRNA anticodon that lines up is of a type that brings an unsuitable amino acid.
H. The ovum (female egg) receives a high radiation dose
C, H, D, A, G, B, F, E
3. The following is one strand of an unwound DNA molecule. Draw the other strand, labeling its 5' and 3' ends. (3 pts)
5'------------------------------3'
3'-----------------------5'
4. The process of nondisjunction could result in an individual with Klinefelter's syndrome (XXY sex chromosomes). (3 pts)
5. Trisomy 21 is also known as Down's syndrome. (3 pts)
6. A recombinant DNA molecule is constructed by allowing the complementaryends of a DNA fragment and a plasmid that have been cut with the same restriction enzyme to associate by base pairing. The single-stranded ends are then covalently joined together by DNA ligase. (6 pts)
7. Give an example of an application of genetic engineering/recombinant DNA technology? (3 pts)
We went over a number of examples. To get full credit you needed to give enough detail to prove your understanding of the procedure.
For example: inserting the gene for human insulin in a plasmid vector using recombinant DNA technology, amplifying the plasmid in E. coli, and isolating the recombinant insulin protein from E. coli.
8. Nucleotides in a DNA strand are covalently joined to one another by phosphodiester linkages. (3 pts)
Brief Essay (40 pts total)
1.The following is the pedigree of a family in which some members suffer from Tay-Sachs disease. Tay-Sachs is a lethal disorder caused by a defect in lipid metabolis
A. What is the mode of inheritance of this disorder? autosomal recessive
(4 pts)
B. Proponents of the discredited eugenics movement believe that the human population would be improved if individuals suffering from genetic disorders, such as Tay-Sachs, could be sterilized or persuaded not to have children. Would implementation of this strategy eliminate these defects? Why or why not? (6 pts)
No. You can carry the allele for the disorder and not express the disorder in the heterozygous state. Hence, sterilizing people with the disorder will not eliminate the defective allele from the population.
2. Briefly describe 2 ways in which transcription and replication are similar, and 2 ways in which they differ. (10 pts)
There were a multitude of possibilities here. We went over several in detail in class on Fri 4/3. Check your notes.
3. Sketch the process of translation during the elongation phase. Label the following: small ribosomal subunit, large ribosomal subunit, tRNA in the P site, incoming tRNA, growing polypeptide chain, mRNA, codon, anticodon. (10 pts)
see your text
4. Briefly describe 3 ways in which eukaryotic gene expression can be controlled. (10 pts)
Again, there were a multitude of possibilities. Check your notes from Fri 4/10
ExtraCredit (5pts)
Diagram the process by which Dolly the sheep was cloned.
This question was aimed at the 20 students who attended class on Fri 3/20.
1. nucleus removed from an adult sheep cell.
2. adult nucleus injected into a sheep egg cell which has had its own nucleus removed
3. egg allowed to go through several cell divisions to form an embryo
4. embryo implanted in surrogate mother sheep
5. Dolly born