Ch 15 HW

helicase

-binds at the replication fork -breaks H-bonds between nitrogenous bases

For the Meselson-Stahl experiment shown in Figure 15.5, what would be the composition of the DNA after three generations?

3/4 low-density and 1/4 intermediate-density

Imagine that the DNA strand shown below serves as the template for DNA synthesis. 5' CATGCATAGA 3' Assuming no errors in DNA synthesis, what would the new DNA look like?

5' TCTATGCATG 3'

What would be the consequence(s) for DNA synthesis if primase were defective?

Both leading and lagging strand synthesis would be incomplete.

The Hershey-Chase experiment answered the question of whether protein or DNA was the genetic material by learning whether ______.

DNA or protein from a virus entered bacterial cells during infection

What catalyzes DNA synthesis?

DNA polymerase

The researchers used strands of DNA located at the ends of chromosomes (called telomeres) to classify the cells they studied. What assumption did they make about telomeres?

Longer telomeres indicate younger cells.

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

Phosphate groups

Which of the following enzymes creates a primer for DNA polymerase?

Primase

The synthesis of a new strand begins with the synthesis of a(n) _____.

RNA primer complementary to a preexisting DNA strand

Which of the following statements about Okazaki fragments in E. coli is true?

They are formed on the lagging strand of DNA.

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

Topoisomerase

What is the relationship between defective DNA repair and cancer?

defective DNA repair→ the increased number of mutations→ the increased probability that cancer-causing mutations will occur

The research showed that individuals who _______ had younger looking cells based on telomere measurements.

exercised for an average of 30 minutes per day

The first step in the replication of DNA is catalyzed by _____.

helicase

Which of the following damages cells and causes cell aging?

inflammation

The researchers found that telomeres were ______.

longer in individuals who exercised regularly

Research indicates that the best estimate of your age is from ______.

markers in your cells

Okazaki fragments are found ______.

only on the lagging strand

Telomerase is needed to ______.

prevent the loss of DNA bases at the ends of linear chromosomes

Topoisomerase works to ______.

prevent twisting of DNA in front of the replication fork

The action of helicase creates _____.

replication forks and replication bubbles

The primers used for DNA synthesis are ______.

short RNA sequences

What is the function of primase?

synthesis of a short RNA, complementary to single-stranded DNA

The polarity of a DNA strand refers to the fact that ______.

the two ends of the strand have different chemical groups

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.

thymine ... cytosine

topoisomerase

-breaks covalent bonds in DNA backbone -binds outside the replication bubbl

leading strand

-made continuously -only one primer needed -daughter strand elongates toward replication fork

lagging strand

-made in segments -multiple primers needed -daughter strand elongates away from replication fork

single-strand binding protein

-prevents H-bonds between bases -binds inside the replication bubble

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

DNA polymerase can assemble DNA only in the 5' to 3' direction

True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.

True

In which image will adenine (A) be the next nucleotide to be added to the primer?

b.

Which of the following statements about DNA synthesis is true? a. As DNA polymerase moves along the template strand, each new nucleotide provides a 5' hydroxyl group for the next reaction to occur. b. Primers are short sequences that allow the initiation of DNA synthesis. c. Nucleotides are added in a random fashion to single-stranded DNA. d. DNA polymerase adds dNTP monomers in the 3' to 5' direction.

b. Primers are short sequences that allow the initiation of DNA synthesis.

The cells examined from the 2,400 people in this study were from ______.

blood

After DNA replication is completed, _____.

each new DNA double helix consists of one old DNA strand and one new DNA strand

Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.

earliest: a & h b & g c & f latest: d & e

Drag the labels to their appropriate locations in the flowchart below, indicating the sequence of events in the production of fragment B.

pol III binds to 3' end of primer B-> pol III moves 5' to 3', adding DNA nucleotides to primer B-> pol I binds to 5' end of primer A-> pol I replaces primer A with DNA-> DNA ligase links fragments A and B

both leading and lagging strands

synthesized 5' to 3

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

template