chapter 17 q & a

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1

Which of the following variations on translation would be most disadvantageous for a cell

translating polypeptides directly from DNA

2

The nitrogenous base adenine is found in all members of which group?

ATP, RNA, and DNA

3

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'. ****************

4

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

5

Which of the following nucleotide triplets best represents a codon?

a triplet in the same reading frame as an upstream AUG

6

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

7

Which of the following does not occur in prokaryotic eukaryotic gene expression, but does in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

8

What is a ribozyme?

an RNA with enzymatic activity

9

In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?

the various domains of the polypeptide product

10

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that

proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

11

Which of the following is the first event to take place in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

12

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by

a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.

13

Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu).

One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.

14
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enzyme a ~~~~> B ~~~~~~>C

2

15

A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?

an accumulation of A and no production of B and C

16

A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3' AAA-GAA-TAA-CAA 5'.

17

What amino acid sequence will be generated, based on the following mRNA codon sequence?
5' AUG-UCU-UCG-UUA-UCC-UUG 3'

met-ser-ser-leu-ser-leu

18
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A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide?

5' TTT-CCC-AAA-GGG-TTT-CCC

19

DNA template strand
5' ____________________________ 3'

DNA complementary strand
3' ____________________________ 5'

In the transcription event of the previous DNA, where would the promoter be located?

to the right of the template strand

20

Which of the following mutations would be most likely to have a harmful effect on an organism

a single nucleotide insertion downstream of, and close to, the start of the coding sequence