Cell Bio Test 2

Which of the following DNA sequences is not commonly carried on mobile genetic elements? You may choose more than one option.

Holliday junction

Which of the following statements is not an accurate statement about thymidine dimers?

(b) Thymidine dimers are covalent links between thymidines on opposite DNA strands.

You are examining the DNA sequences that code for the enzyme phosphofructokinase in skinks and Komodo dragons. You notice that the coding sequence that actually directs the sequence of amino acids in the enzyme is very similar in the two organisms but that the surrounding sequences vary quite a bit. What is the most likely explanation for this?

(d) Mutations in coding sequences are more likely to be deleterious to the organism than mutations in noncoding sequences.

The repair of mismatched base pairs or damaged nucleotides in a DNA strand requires a multistep process. Which choice below describes the known sequence of events in this process?

DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase.

If the genome of the bacterium E. coli requires about 20 minutes to replicate itself, how can the genome of the fruit fly Drosophila be replicated in only 3 minutes?

Drosophila DNA contains more origins of replication than E. coli DNA.

All functional DNA sequences inside a cell code for protein products.

False

DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits.

False

The polarity of a DNA strand results from the polarity of the nucleotide subunits.

False

There are five different nucleotides that become incorporated into a DNA strand.

False

Comparing the relative number of chromosome pairs is a good way to determine whether two species are closely related.

False-Same number of genes different number of chromosomes

You have discovered an "Exo-" mutant form of DNA polymerase in which the 3′-to-5′ exonuclease function has been destroyed but the ability to join nucleotides together is unchanged. Which of the following properties do you expect the mutant polymerase to have?

It will be more likely to generate mismatched base pairs. DNA polymerase proofreads 3 to 5 (exonuclease) and it polymerizes in 5 to 3.

You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon. Which of the following statements describes the most likely effect of this mutation on Abd transcription?

The Abd RNA from the mutant strain will be longer than normal.

Each strand of DNA contains all the information needed to create a new double-stranded DNA molecule with the same sequence information.

True

Eucaryotic chromosomes contain many different sites where DNA replication can be initiated.

True

Hydrogen bonds between each nucleotide hold individual DNA strands together.

True

DNA replication is considered semi-conservative because __________________.

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand

Transcription is similar to DNA replication in that ___________________.

nucleotide polymerization occurs only in the 5′-to-3′ direction

The images of chromosomes we typically see are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and __________________________.

occupy discrete territories in the nucleus

The DNA from two different species can often be distinguished by a difference in the ______________________.

ratio of A + T to G + C

Which of the following chemical groups is not used to construct a DNA molecule?

six-carbon sugar

In a DNA double helix, _____________________

A. the two DNA strands run antiparallel

Because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds. Every unique DNA molecule "melts" at a different temperature. In this context, Tm, melting temperature, is the point at which two strands separate, or become denatured. Which DNA sequence will result in the highest Tm, assuming they start out as a double stranded DNA molecule?

GGCGCACC Look for G&C triple bond

The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does not form part of the octameric core?

H1-Two molecules of each histone H2a, h2b, h3, and h4, and wraps around the histone octamer.