Unit 5

At a specific area of a chromosome, the following sequence of nucleotides is present where the chain opens to form a replication fork:3' C C T A G G C T G C A A T C C 5'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'

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%

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.

Two potential devices that eukaryotic cells use to regulate transcription are

DNA methylation and histone modification

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

DNA polymerase III

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

Which of the enzymes separates the DNA strands during replication?

I

Which of the enzymes covalently connects segments of DNA?

III

Which of the following is not true of a codon?

It extends from one end of a tRNA molecule

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your kidney cells.

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.

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

The amino acid binds covalently.

The tRNA shown in Figure 14.5 has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

The amino acid binds covalently.

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

The cell's DNA couldn't be packed into its nucleus.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find?

The molecules digested by exnucleases because it is no longer protected at the 5' end

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

V

Which of the enzymes synthesizes short segments of RNA?

V

How do we describe transformation in bacteria?

assimilation of external DNA into a cell

Steroid hormones produce their effects in cells by

binding to intracellular receptors and promoting transcription of specific genes.

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.

Alternative RNA splicing

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

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon.

In a nucleosome, the DNA is wrapped around

histones.

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

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.

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.