Chapter 21 - DNA

Question 1

What is a chromosome?

Answer 1

A long strand of DNA that is tightly packed.

Question 2

What is DNA?

Answer 2

A molecule that carries genetic instructions.

Question 3

What is a gene?

Answer 3

A section of DNA that codes for a protein

Question 4

What does each gene code for?

Answer 4

A protein.

Question 4

How do proteins affect traits?

Answer 4

Proteins control traits like eye color and blood type.

Question 5

What are nucleic acids made of?

Answer 5

Nucleotides.

Question 5

What did their model show?

Answer 5

DNA is a double helix with specific base pairing.

Question 6

What bases pair together?

Answer 6

A with T, G with C.

Question 7

What are the four DNA bases?

Answer 7

Adenine (A), Thymine (T), Guanine (G), Cytosine (C).

Question 8

What are the three parts of a nucleotide?

Answer 8

Sugar (deoxyribose), phosphate group, nitrogen base.

Question 8

What does antiparallel mean?

Answer 8

One DNA strand runs 5′→3′, the other runs 3′→5′.

Question 8

What is the shape of DNA?

Answer 8

Double helix (twisted ladder).

Question 9

Who discovered DNA’s structure and when?

Answer 9

Watson and Crick in 1953.

Question 9

What is the 3′ end?

Answer 9

Has an –OH (hydroxyl) group on the 3′ carbon.

Question 10

How are bases held together?

Answer 10

Hydrogen bonds.

Question 11

How many hydrogen bonds?

Answer 11

A–T = 2, C–G = 3.

Question 12

What is the 5′ end?

Answer 12

Has a phosphate group on the 5′ carbon.

Question 13

What sugar does RNA use?

Answer 13

Ribose.

Question 14

Is RNA single or double stranded?

Answer 14

Single stranded.

Question 15

What base replaces thymine in RNA?

Answer 15

Uracil (U).

Question 16

How many main types of RNA are there?

Answer 16

Three. mRNA, tRNA, rRNA

Question 17

What is tRNA?

Answer 17

Brings amino acids to ribosomes.

Question 17

What is rRNA?

Answer 17

Makes up ribosomes.

Question 17

What is mRNA?

Answer 17

Carries genetic code from DNA to ribosomes.

Question 18

What does semi-conservative mean?

Answer 18

Each new DNA has one old strand and one new strand.

Question 18

Why is DNA replication important?

Answer 18

So each new cell gets the same DNA.

Question 19

When does DNA replication occur?

Answer 19

S phase of the cell cycle.

Question 20

What enzyme copies DNA?

Answer 20

DNA polymerase.

Question 21

Which DNA polymerase does synthesis?

Answer 21

DNA Pol III.

Question 22

What does helicase do?

Answer 22

Unzips DNA by breaking hydrogen bonds.

Question 22

: Which polymerases repair DNA?

Answer 22

DNA Pol I and DNA Pol II.

Question 23

What are the three stages of DNA replication?

Answer 23

Initiation, Elongation, Termination.

Question 24

What does primase do?

Answer 24

Adds RNA primers to start replication.

Question 25

What is the leading strand?

Answer 25

Made continuously in the 5′→3′ direction.

Question 26

What is the lagging strand?

Answer 26

Made in pieces called Okazaki fragments.

Question 27

What enzyme joins fragments?

Answer 27

DNA ligase.

Question 27

In what direction is DNA always made?

Answer 27

5′→3′.

Question 28

What is DNA proofreading?

Answer 28

DNA polymerase fixes mistakes during replication.

Question 28

What happens during termination?

Answer 28

Replication stops, primers removed, DNA filled in.

Question 28

Why does the lagging strand form fragments?

Answer 28

It’s built opposite the fork’s direction.

Question 29

What does DNA ligase do?

Answer 29

Glues Okazaki fragments together.

Question 30

What is exonuclease activity?

Answer 30

Removes incorrect nucleotides.

Question 31

How many origins of replication?

Answer 31

Prokaryotes: 1 | Eukaryotes: many.

Question 32

DNA shape difference?

Answer 32

Prokaryotes: circular | Eukaryotes: linear.

Question 33

Which replicates faster?

Answer 33

Prokaryotes.

Question 34

Why is eukaryotic replication slower?

Answer 34

DNA is wrapped around histones.

Question 35

Why don’t prokaryotes need telomerase?

Answer 35

Their DNA is circular.

Question 36

Why do eukaryotes need telomerase?

Answer 36

DNA is linear and shortens each replication.

Question 37

What does telomerase do?

Answer 37

Extends chromosome ends using an RNA template.

Question 38

What repeat does telomerase add?

Answer 38

TTAGGG.