Biology 11. DNA Synthesis Multiple Choice

What kind of chemical bond is found between paired bases of the DNA double helix? a. hydrogen b. phosphate c. ionic d. sulfhydryl e. covalent

a. hydrogen

Which of the following separates the DNA strands during replication? a. DNA polymerase III b. primase c. helicase d. ligase e. DNA polymerase I

c. helicase

At a specific area of a chromosome, the sequence of nucleotides below 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? a. 5' G C C U A G G 3' b. 5' G C C T A G G 3' c. 5' A C G T T A G G 3' d. 3' G C C T A G G 5' e. 5' A C G U U A G G 3'

e. 5' A C G U U A G G 3'

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? a. 12 b. 21 c. 38 d. 24 e. It cannot be determined from the information provided.

a. 12

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction? a. DNA polymerase III b. primase c. DNA ligase d. topoisomerase e. helicase

a. DNA polymerase III

A new DNA strand elongates only in the 5' to 3' direction because: a. DNA polymerase can only add nucleotides to the free 3' end. b. Okazaki fragments prevent elongation in the 3' to 5' direction. c. the polarity of the DNA molecule prevents the addition of nucleotides at the 3' end. d. DNA polymerase begins adding nucleotides at the 5' end of the template. e. replication must progress toward the replication fork.

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

When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result? a. The viral proteins will be radioactive. b. The bacterial DNA will be radioactive. c. The viral DNA will be radioactive. d. both A and B e. both A and C

a. The viral proteins will be radioactive.

What is the function of topoisomerase? a. relieving strain in the DNA ahead of the replication fork b. stabilizing single-stranded DNA at the replication fork c. the addition of methyl groups to bases of DNA d. elongation of new DNA at a replication fork by addition of nucleotides to the existing chain e. unwinding of the double helix

a. relieving strain in the DNA ahead of the replication fork

Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that: a. the amount of A is always equivalent to T, and C to G. b. the amount of ribose is always equivalent to deoxyribose. c. transformation causes the protein to be brought into the cell. d. the human genome is more complex than that of other species. e. the relative proportion of each of the four bases differs within individuals of a species.

a. the amount of A is always equivalent to T, and C to G.

In an analysis of the nucleotide composition of DNA, which of the following will be found? a. A = G and C = T b. A + C = G + T c. G + C = T + A d. A = C

b. A + C = G + T

Which of the following removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? a. helicase b. DNA polymerase I c. ligase d. DNA polymerase III e. primase

b. DNA polymerase I

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? a. catalyzes the lengthening of telomeres b. join Okazaki fragments together c. synthesize RNA nucleotides to make a primer d. stabilize the unwound parental DNA e. unwind the parental double helix

b. join Okazaki fragments together

Which of the following synthesizes short segments of RNA? a. ligase b. primase c. helicase d. DNA polymerase I e. DNA polymerase III

b. primase

Which of the following covalently connects segments of DNA? a. helicase b. DNA polymerase III c. ligase d. primase e. DNA polymerase I

c. ligase

What is the function of DNA polymerase III? a. to degrade damaged DNA molecules b. to unwind the DNA helix during replication c. to add nucleotides to the end of a growing DNA strand d. to seal together the broken ends of DNA strands e. to rejoin the two DNA strands (one new and one old) after replication

c. to add nucleotides to the end of a growing DNA strand

An Okazaki fragment has which of the following arrangements? a. DNA polymerase I, DNA polymerase III b. 3' RNA nucleotides, DNA nucleotides 5' c. 5' DNA to 3' DNA d. 5' RNA nucleotides, DNA nucleotides 3' e. primase, polymerase, ligase

d. 5' RNA nucleotides, DNA nucleotides 3'

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? a. The origins of replication occur only at the 5' end. b. DNA ligase works only in the 3' → 5' direction. c. Helicases and single-strand binding proteins work at the 5' end. d. DNA polymerase can join new nucleotides only to the 3' end of a growing strand. e. Polymerase can work on only one strand at a time.

d. DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

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? a. Replication will require a DNA template from another source. b. No proofreading will occur. c. The DNA will supercoil. d. No replication fork will be formed. e. Replication will occur via RNA polymerase alone.

d. No replication fork will be formed.

Which of the following help to hold the DNA strands apart while they are being replicated? a. DNA polymerase b. primase c. exonuclease d. ligase e. single-strand binding proteins

e. single-strand binding proteins