cells bio hw 12

1. During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a____ 2. The new DNA strand that grows continuously in the 5' to 3' direction is called the 3 After replication is complete, the new DNAs, called______, are identical to each other. 4 The enzyme that can replicate DNA is called 5_____are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.

1. replication fork. 2. leading strand 3. daughter DNA 4. DNA polymerase. 5. Okazaki fragments

Put the following steps of DNA replication in chronological order. 1. Single-stranded binding proteins attach to DNA strands. 2. Hydrogen bonds between base pairs of antiparallel strands are broken. 3. Primase binds to the site of origin. 4. DNA polymerase binds to the template strand. 5. An RNA primer is created.

2, 1, 3, 5, 4

If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?

3'-TAAACG-5' remember that numbers switch

By convention, biologists write the sequence of bases in RNA and DNA in which direction?

5′→3′

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?

75 100 nucleotide pairs are a total of 200 nucleotides. Because of base pairing, if there are 25 adenine there must also be 25 thymine. This leaves 200-50 = 150 nucleotides to be divided evenly between guanine and cytosine.

Refer to the figure. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the order that they will be added starting at the 5' end of the new strand.

A, G, A, C, G, A, C

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

Both leading and lagging strand synthesis would be incomplete.

Which of these is a difference between a DNA and an RNA molecule?

DNA is usually double-stranded, whereas RNA is usually single-stranded.

DNA contains the template needed to copy itself, but as you learned in Chapter 4, it has no catalytic activity. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?

DNA polymerase

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. 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 either in short 5' to 3' segments, which are later joined together by ligase, or be assembled continuously.

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

Lagging strand synthesis would be incomplete; leading strand synthesis would be unaffected.

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

RNA primer complementary to a preexisting DNA strand

What is the difference between a ribonucleotide and a deoxyribonucleotide?

Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit. the green is removed on deoxyribonucleotide

What is the difference between the leading strand and the lagging strand in DNA replication?

The leading strand is synthesized continuously in the 5→3 direction, while the lagging strand is synthesized discontinuously in the 5'-3' direction.

Which of the following nitrogenous bases are purines?

adenine and guanine

What are the four nitrogenous bases found in RNA?

adenine, uracil, guanine, cytosine (A, U, G, C)

In the accompanying image, a nucleotide is indicated by the letter

b

The fact that within a double-stranded DNA molecule, adenine forms two hydrogen bonds with thymine and cytosine forms three hydrogen bonds with guanine is known as ________.

complementary base pairing.

Which of the following includes all of the pyrimidines found in RNA and/or DNA?

cytosine, uracil, and thymine

After DNA replication is completed,

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

The first step in the replication of DNA is catalyzed by

helicase

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.

hydrogen bonds

What is responsible for holding the two strands together in the DNA double helix?

hydrogen bonds

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

ligase

Semiconservative replication involves a template. What is the template?

one strand of the DNA molecule

A nucleotide is composed of a(n) _____.

phosphate group, a nitrogen-containing base, and a five-carbon sugar

The action of helicase creates

replication forks and replication bubbles

DNA is synthesized through a process known as ________.

semiconservative replication.

The primers used for DNA synthesis are _____.

short RNA sequences

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

template

In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _____ of the last nucleotide in the polymer.

the 3' OH

What provides the energy for the polymerization reactions in DNA synthesis?

the deoxyribonucleotide triphosphate substrates

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