DNA Replication: A Closer Look

Part A

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.

	guanine ... adenine
	thymine ... cytosine
	cytosine ... uracil
	cytosine ... thymine
	uracil ... cytosine

Correct

This is referred to as specific base pairing.

Part B

After DNA replication is completed, _____.

	each of the four DNA strands consists of some old strand parts and some new strand parts
	each new DNA double helix consists of one old DNA strand and one new DNA strand
	there are four double helices
	one DNA double helix consists of two old strands and one DNA double helix consists of two new strands
	each new DNA double helix consists of two new strands

Correct

DNA replication is semiconservative.

Part C

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

	helicase
	single-strand binding protein
	ligase
	DNA polymerase
	primase

Correct

The first step of DNA replication is unwinding the DNA double helix.

Part D

The action of helicase creates _____.

	DNA fragments and replication bubbles
	DNA fragments and replication forks
	primers and replication bubbles
	primers and DNA fragments
	replication forks and replication bubbles

Correct

A replication fork is the transition region between paired and unpaired DNA strands.

Part E

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

	only short DNA sequences can extend off the RNA primers
	the replication forks block the formation of longer strands
	DNA polymerase can assemble DNA only in the 3' to 5' direction
	DNA polymerase can assemble DNA only in the 5' to 3' direction
	it is more efficient than assembling complete new strands

Correct

Since DNA polymerase can assemble DNA only in the 5' to 3' direction, the new strand complementary to the 3' to 5' strand must be assembled in short 5' to 3' segments, which are later joined together by ligase.

Part F

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

	RNA primer complementary to a preexisting DNA strand
	single-strand binding protein
	short pieces of DNA
	Okazaki fragment
	poly(A) tail

Correct

The synthesis of a DNA strand begins with the formation of an RNA primer.

Part G

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

	primer
	source of nucleotides
	template
	model
	complement

Correct

An old DNA strand is used as a template for the synthesis of a complementary new strand.