Ch. 9

Question 1

Nucleotide

Answer 1

a single building block composed of a deoxyribose sugar, a phosphate group, and a nitrogenous base

Question 2

Nitrogenous bases

Answer 2

Adenine, Guanine = purines
cytosine, thymine = pyrimidines

Question 3

Sugar phosphate backbone

Answer 3

chained nucleotides

5’ ends w phosphate group on backbone
3’ ends w hydroxyl group

Question 4

Which DNA fragment is more resistant to heat?

Answer 4

GC fragments bc it has 3 hydrogen bonds, while AT has 2 hydrogen bonds

Question 5

Chromatin

Answer 5

chromosome substance where DNA is wrapped in several layers
protein DNA complex that makes up eukaryotic chromosomes

Question 6

Semiconservative

Answer 6

two identical double helices are formed from one original, parental double helix, and each DNA double helix has half original and half kinda new strand

Question 7

DNA Replication (in S phase)

Answer 7

1. Parent DNA molecule
2. Parental strands unwind and separate at several points
3. Parental strand has template where DNA polymerase binds complementary bases (A-T and G-C)

Question 8

Enzymes in DNA Replication

Helicase

Answer 8

unwinds parental double helix

Question 9

Enzymes in DNA Replication

Binding proteins

Answer 9

stabilize separate strands

Question 10

Enzymes in DNA Replication

Primase

Answer 10

adds short primer to template strand

Question 11

Enzymes in DNA Replication

DNA polymerase

Answer 11

binds nucleotides to form new strands

Question 12

Enzymes in DNA Replication

Ligase

Answer 12

joins Okazaki fragments and seals other nicks in sugar-phosphate backbone

Question 13

Polymerase Chain Reaction (PCR)

Answer 13

DNA amplification technique

DNA polymerase replicate specific DNA sequence in test tube

Question 14

Sequencing DNA

Answer 14

deduces a DNA sequence by aligning pieces that differ from each other by the end base

reverse transcription

Question 15

Reading a DNA sequence

Answer 15

1. DNA fragments are ordered by size on sequencing gel (by longest to shortest)
2. Laser highlights end base
3. Sequence is derived

Question 16

Histone

Answer 16

individual proteins that DNA is wrapped around

Question 17

Nucleosome

Answer 17

structure resembling beads on string

Question 18

metaphase chromosome

Answer 18

highly compacted replicated DNA

Question 19

The copying of the information in DNA is straightforward because

Answer 19

each strand of a DNA molecule carries complementary information.

Question 20

Replication occurs at a

Answer 20

replication fork

Question 21

The DNA double helix is separated into single strands by the enzyme

Answer 21

helicase

Question 22

Short segments of RNA, called ___ , are synthesized.

Answer 22

RNA primers

Question 23

Newly-exposed, unreplicated DNA is protected by

Answer 23

binding proteins

Question 24

The enzyme that synthesizes the short segments of RNA is called a

Answer 24

primase

Question 25

New DNA is synthesized in the ___ direction.

Answer 25

5’ to 3’

Question 26

The enzyme that catalyzes new DNA synthesis is

Answer 26

DNA polymerase

Question 27

Fragments of discontinuous DNA synthesis are called

Answer 27

Okazaki fragments

Question 28

Gaps in the sugar-phosphate backbone of DNA are closed by

Answer 28

DNA ligase

Question 29

What components are needed to perform PCR?

Answer 29

target DNA, DNA primers, DNA nucleotides, and Taq1 polymerase.

Question 30

Imagine you are able to watch DNA replication under a microscope in a mutant strain of bacteria. DNA replication appears to proceed normally, but at the end of the replication cycle, there are some regions of the DNA that appear to be fragmented and not joined together along the backbone of the DNA molecule.

Which enzyme is most likely missing in this bacterial strain?

Answer 30

ligase

Question 31

You are performing PCR for the first time in the lab. You have all your reagents ready, but you forgot to add adenine.

What will be the result of your reaction?

Answer 31

DNA synthesis will occur until the polymerase reaches a thymine in the template strand, and then it will halt.

Question 32

You are working with a novel organism with double-stranded DNA and you discover that this organism has 20% adenine in its DNA.

What percentage of cytosine do you expect that this organism has in its DNA?

Answer 32

30%; in DNA the amount of adenine equals the amount of thymine, and the amount of cytosine equals the amount of guanine. If the percentage of adenine is 20%, we also expect the % of thymine to be 20%. This leaves 60% of the DNA for cytosine and guanine. Because we expect equal amounts of each of these, we expect 30% cytosine.