bio 5

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism.

Which component is not directly involved in translation?

DNA

Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

DNA Polymerase I (RNase)

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

DNA contains phosphorus, whereas protein does not.

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?

The entire template molecule is represented in the product.

Which of the following statements is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

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 also include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

several transcription factors (TFs)

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

single-strand binding proteins

The leading and the lagging strands differ in that

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

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'.

Given the locally unwound double strand above, in which direction does the RNA polymerase move?

3' ® 5' along the template strand

An RNA primer is formed starting at the underlined T ( T) of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3'

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

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

ATP, RNA, and DNA

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure above would be expected after one round of DNA replication in the presence of 14N?

D

Which enzyme catalyzes the elongation of a DNA strand in the 5' 3' direction?

DNA polymerase III

A new DNA strand elongates only in the 5' to 3' direction because

DNA polymerase can only add nucleotides to the free 3' end.

Which of the following investigators was/were responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Erwin Chargaff

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?

It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication.

Which of the following statements describes the eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

Which of the following is not true of a codon?

It extends from one end of the tRNA molecule

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together.

Why might a point mutation in DNA make a difference in the level of a protein's activity?

It might substitute a different amino acid in the active site of the protein.

When the function of the newly made polypeptide is to be secreted from the cell where it has been made, what must occur?

Its signal sequence must target it to the ER, from which it goes to the Golgi Apparatus.

In his transformation experiments, what did Griffith observe?

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. which of the following would you expect as a result of this mutation

No replication fork will be formed

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

Of the following, which is the most current description of a gene?

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

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

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

What is a ribozyme?

an RNa with enzymatic activity

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

How do we describe transformation in bacteria?

assimilation of external DNA into a cell

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs

Alternatic RNA splicing

can allow the production of proteins of different sizes from a single mRNA

the anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon

A frameshift mutation could result from

either an insertion or a deletion of a base.

In a nucleosome, the DNA is wrapped around

histones

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

many noncoding stretches of nucleotides are present in eukaryotic DNA.

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

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that

the rules for base pairing between the third base of a codon and tRNA are flexible.

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?

the sequence of bases

When the spliceosome binds to elements of this structure, where can it attach?

to the end of an intron

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

to the right of the template strand