Video Tutor Session Quiz: DNA Structure

Part A

Correct

In this model, the deoxyribose sugar is the blue five-sided structure at the center.

Part B

Correct

A polynucleotide contains a sugar/phosphate backbone, where the sugar of one nucleotide binds to the phosphate of the next, and so on.

Part C

Correct

Remember the base pairing rules: A goes with T, and G goes with C. So the sequence GCAC matches with the sequence CGTG.

Part D

Correct

There are four kinds of DNA nucleotides, abbreviated A, T, C, and G.

Part E

Correct

The sugar and phosphate groups are the same for all DNA nucleotides. The base is the one part that changes.

DNA Packing

Part A

The letter A indicates _____.

	supercoils
	a nucleosome
	a DNA double helix
	histones
	loops

Correct

This is a decondensed DNA double helix.

Part B

Where would RNA polymerase attach?

	A
	B
	C
	A and B
	B and C

Correct

RNA polymerase attaches to DNA.

Part C

The letter C indicates _____.

	supercoils
	a nucleosome
	a DNA double helix
	histones
	loops

Correct

These are histone proteins.

Part D

What is this an image of?

	supercoils
	a nucleosome
	a DNA double helix
	histones
	loops

Correct

This is an image of supercoils.

Part E

What is this an image of?

	supercoils
	a nucleosome
	a DNA double helix
	histones
	loops

Correct

This is an image of loops.

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.

DNA Replication: A Review

Part A

Short segments of newly synthesized DNA are joined into a continuous strand by _____.

	DNA polymerase
	primase
	single-strand binding protein
	helicase
	ligase

Correct

Ligase joins DNA segments into a continuous strand.

Part B

After DNA replication is completed, _____.

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

Correct

DNA replication is semiconservative.

Part C

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

	DNA polymerase
	ligase
	primase
	single-strand binding protein
	helicase

Correct

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

Part D

The action of helicase creates _____.

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

	DNA polymerase can assemble DNA only in the 3' to 5' direction
	DNA polymerase can assemble DNA only in the 5' to 3' direction
	the replication forks block the formation of longer strands
	only short DNA sequences can extend off the RNA primers
	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) _____.

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

Correct

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

Part G

Which of these is responsible for catalyzing the formation of an RNA primer?

	D
	C
	A
	B
	E

Correct

Primase catalyzes the formation of an RNA primer.

Part H

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

	model
	primer
	template
	complement
	source of nucleotides

Correct

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