Chp 13 - Molecular Basis of Inheritance

FAWWK

The experiments of Meselson and Stahl showed that DNA __________.

DNA replicates in a semiconservative manner

The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called __________.

topoisomerase

During Griffith's experiments with Streptococcus pneumoniae in mice, material from __________ bacteria transformed __________ bacteria.

heat-killed virulent; living nonvirulent

Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?

• Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.

Who is credited with discovering the structure of the DNA double helix?

Watson & Crick

A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have __________.

• the protein and DNA of T4

What does DNA form between the rungs?

Hydrogen bonds

What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?

• X-ray crystallography

The two strands of a DNA double helix are antiparallel. This means that __________.

• one strand runs in the 5' to 3' direction and the other runs in the 3' to 5' direction

What is the major difference between bacterial chromosomes and eukaryotic chromosomes?

• Bacteria have a single circular chromosome, whereas eukaryotes have several linear chromosomes.

Which of the following components is required for DNA replication?

RNA Primers

The role of DNA polymerases in DNA replication is to __________.

• attach free nucleotides to the new DNA strand

DNA polymerase adds nucleotides to the __________ of the leading strands and to the __________ of the lagging strands (Okazaki fragments).

• 3' end; 3' end

Which of the following lists is in order from the entity with the smallest genome to the entity with the largest genome?

Virus, bacteria, eukaryote

The incorporation of an incorrect base into a DNA molecule during replication __________.

• can be repaired by the mismatch repair system

Avery and his colleagues' 1944 experiment showed that DNA __________.

• was the substance that transformed the bacteria in Griffith's experiment

• showed that DNA is the "transforming principle"—the substance responsible for passing genetic information from one bacterial strain to another.

What enzyme joins Okazaki fragments?

• DNA ligase

Which of the following statements about origins of replication is correct?

• In bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin.

• Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins.

• The two strands of DNA at the origin are separated, allowing the formation of a replication bubble.

• In both prokaryotes and eukaryotes, replication proceeds in both directions from each origin.

The "beads on a string" seen in interphase chromatin are __________.

nucelosomes

Chargaff found that in DNA samples, __________.

• the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1

What is the major difference between bacterial chromosomes and eukaryotic chromosomes?

• Bacteria have a single circular chromosome, whereas eukaryotes have several linear chromosomes.

Why were many of the early experiments on DNA carried out on viruses and bacteria?

• Their chromosomes have a simpler structure.

• They have relatively small genomes.

• They have short generation times.

• They can interact with each other.

In DNA, the two purines are __________, and the two pyrimidines are __________.

• adenine and guanine

• cytosine and thymine

The rate of elongation of a DNA strand in prokaryotes is __________ the rate in eukaryotes.

MUCH faster

The overall error rate in a completed DNA molecule is approximately __________.

• one error per 10,000,000,000 nucleotides

In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.

1 to 5

Nucleic acids are assembled in the _____ direction.

5’ → 3’

DNA is a self-replicating molecule. What accounts for this important property of DNA?

The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.

Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?

Hydrolysis of the two phosphate groups (P-P_i) and DNA polymerization are a coupled exergonic reaction

Select the most accurate statement describing DNA replication complexes.

DNA replication complexes are grouped into factories, which are anchored to the nuclear matrix.