Mastering Biology Chapter 15

chromosomes contain genes

A shell of protein enclosing the genome of a virus particle

The secondary structure of DNA, consisting of two antiparallel DNA strands wound around each other

Hydrogen bonds that form between the bases of Adenine (A) and Thymine (T) and between the bases guanine (G) and cytosine (C), along with hydrophobic interactions that the bases experience inside the helix.

The association between specific nitrogenous bases of nucleic acids stabilized by hydrogen bonding. Adenine pairs only with thymine (in DNA) or uracil (in RNA), and guanine pairs only with cytosine.

the way DNA replicates, in which each strand of an existing DNA molecule serves as a template to create a new complementary DNA strand. It is called semiconservative because each newly replicated DNA molecule conserves one of the parental strands and contains another, newly replicated strand.

strands of DNA that are used as templates during DNA synthesis

strands of DNA that are newly replicated from existing template strands of DNA

Alternative hypothesis of how genes replicate. Suggests the bases temporarily turn outward so that complementary strands no longer face each other and serve as a template for the synthesis of an entirely new helix

stretches of old DNA would be interspersed with new DNA down the length of each daughter strand

all the hereditary information in an organism, including not only genes but also stretches of DNA that do not contain genes

True

an enzyme that catalyzes synthesis of DNA from deoxyribonucleotide triphosphates (dNTPs).

False. DNA always proceeds in the 5' -> 3' direction.

False. DNA polymerases can add deoxyribonucleotides only to the 3' end of a growing DNA chain.

DNA synthesis is exergonic because the monomers that are used in the DNA synthesis reaction are deoxyribonucleoside triphosphates (dNTPs).

the site on the chromosome at which DNA replication begins

at the origin of replication

False. Bacterial chromosomes have only one origin of replication, but eukaryotes have multiple along each chromosome, causing multiple replication bubbles to form.

True, and because of this, replication bubbles grow in two directions as DNA replication proceeds.

These proteins are activated by the proteins that initiate S phase in the cell cycle.

the Y-shaped site at which a double-stranded molecule of DNA is separated into two single strands for replication

an enzyme that breaks hydrogen bonds between nucleotides of DNA, "unzipping" a double-stranded DNA molecule

proteins that attach to separated strands of DNA during replication or transcription, preventing them from reforming a double helix

an enzyme that prevents the twisting of DNA ahead of the advancing replication fork by cutting the DNA, allowing it to unwind, and rejoining it

The twisting induced by the helicase is relaxed by proteins called topoisomerase.

DNA polymerase also requires a single-stranded template

a short, single-stranded RNA molecule that base-pairs with a DNA template strand and is elongated by DNA polymerase during DNA replication

an enzyme that catalyzes the polymerization of ribonucleotides into RNA

In DNA replication, the strand of new DNA that is synthesized in one continuous piece

True. The other strand must be synthesized in a direction that runs away from the moving replication forks.

In DNA replication, the strand of new DNA that is synthesized discontinuously in a series of short pieces that are later joined

primase synthesizes new RNA primers for lagging strands as the moving replication fork opens single-stranded regions of DNA, and that DNA polymerase uses these primers to synthesize short lagging-stranded DNA fragments that are linked together into a continuous strand

Reiji Okazaki and friends

short segment of DNA produced during replication of the lagging strand template. Many Okazaki fragments make up the lagging strand in newly synthesized DNA

100 to 200 base pairs long

about 1000 base pairs long

an enzyme that joins pieces of DNA by catalyzing the formation of a phosphodiester bond between the spaces

1. Primer added 2. First fragment synthesized 3. Second fragment synthesized. 4. Primer replaced. 5. Gap closed

Primase synthesizes RNA primer.

DNA polymerase III works in 5' -> 3' direction, synthesizing first Okazaki fragment of lagging strand.

Primase and DNA polymerase III synthesize another Okazaki fragment.

DNA polymerase I removes ribonucleotides of primer, replaces them with deoxyribonucleotides in 5' -> 3' direction.

DNA ligase closes gap in sugar-phosphate backbone

The macromolecular machine that copies DNA; including DNA polymerase, helicase, primase, and other enzymes

It catalyzes the breaking of hydrogen bonds between base pairs to open the double helix.

They stabilize single-stranded DNA

It breaks and rejoins the DNA double helix to relieve twisting forces caused by the opening of the helix.

It catalyzes the synthesis of the RNA primer.

It extends the leading strand.

It holds DNA polymerase in place during strand extension.

It catalyzes the synthesis of the RNA primer on an Okazaki fragment.

It extends an Okazaki fragment.

It holds DNA polymerase in place during strand extension.

The end of a linear chromosome that contains a repeated sequence of DNA

1. DNA unwinding completed. 2. Leading strand completed. 3. Lagging strand completed. 4. Lagging strand too short. =(

In order for the lagging strand to be too short, no DNA synthesis must occur after primer is removed.

The single stranded DNA at the end of the lagging strand is eventually degraded, which results in the shortening of the chromosome.

An enzyme that adds DNA to the ends of chromosomes (telomeres) by catalyzing DNA synthesis from an RNA template that is part of the enzyme

It catalyzes the synthesis of DNA from RNA template that it contains

any type of cell in a multicellular organism except eggs, sperm, and their precursor cells

True. For example, in humans, active telomerase is found primarily in the cells that produce gametes.

False. Most cancer cells do, in fact, have active telomerase.

the process by which a DNA polymerase recognizes and removes a wrong base added during DNA replication and then continues synthesis

The process by which mismatched base pairs in DNA are fixed.

when mismatched bases are corrected after DNA synthesis is complete

The process of removing a damaged region in one strand of DNA and replacing it with the correct sequence using the undamaged strand as a template

True.

a human disease characterized by extreme sensitivity to ultraviolet light. Caused by an autosomal recessive allele that inactivates the nucleotide excision DNA repair system.

They have opposite directionality, or polarity.

It adds dNTPs only in the 5' -> 3' direction.

topoisomerase

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

Using the lagging strand template, and synthesizing 5' -> 3'

telomerase

Labeling DNA vs. Labeling protein

DNA

32S

Labeled DNA ... DNA protein

the 3' OH

permits complementary base pairing

leading strand

daughter DNA

replication fork

DNA polymerase

Okazaki fragments

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

Both leading and lagging strand synthesis would be incomplete.

Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

DNA is constantly damaged, and many pathways have evolved to repair this onslaught of damage. If a DNA repair pathway is inactivated by mutation, damage is inefficiently repaired. Consequently mutation rates increase, and the increased number of mutations increase the probability of that cancer-causing mutations will occur.

On the lagging strand, DNA polymerase moves away from the replication fork. When helicase unwinds a new section of DNA, primase must build a new primer on the template for the lagging strand (closer to the fork) and another polymerase molecule must begin synthesis at this point. This makes the lagging-strand synthesis discontinuous. On the leading strand, DNA polymerase moves in the same direction as helicase, so synthesis can continue, without interruption, from a single primer (at the origin or replication).

Telomerase binds to the overhang at the end of a chromosome. Once bound, it begins catalyzing the addition of deoxyribonucleotides to the overhang in the 5' -> 3' direction, lengthening the overhang. This allows primase, DNA polymerase, and ligase to catalyze the addition of deoxyribonucleotides to the lagging strand in the 5' -> 3' direction, restoring the lagging strand to its original length.

The mutation rate would increase.

The regularity of DNA's overall structure

the ability to synthesize DNA in the 3' -> 5' direction

About 4600 seconds (77 minutes). See page A:17 (Ch. 15 No. 16) for details

separate viral protein coats from the bacterial cells in the culture

A section of the DNA containing the mismatched base is removed and replaced.

the 5'

Telomerase

20%

It adds nucleotides to the lagging strand

All of the monomers contain a phosphate group and a nitrogenous base connected to a deoxyribose.

The system detects mutations because they produce an irregularity in the DNA molecule.

Half of the DNA strands contained only the light nitrogen isotope.

XP individuals lack one or more enzymes involving excising damaged DNA bases from the chromosomes.

New nucleotides are added in the 5' to 3' directions of both the lagging and leading strands.

5' TTGGCATTAAGC 3'

True

Are genes made up of protein or DNA?

made up of short DNA/RNA fragments during replication

The 3' of the DNA chain forms a covalent linkage with the phosphate group on the 5' end of the dNTP.

It adds nucleotides to the lagging strand.

DNA polymerase III

Telomerase is involved in adding DNA to the end of the lagging strand

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

gaps left at the 5' end of the lagging strand

Telomerase is active in most cancer cells.

mismatch pair

recognizes and repairs thymine dimers and other damaged bases in DNA

There are several proteins involved in the nucleotide excision repair process.

light from an incandescent bulb