Chapter 9

Question 1

where is DNA present?

Answer 1

cell nucleus and in condensed chromosomes

Question 2

when does DNA double?

Answer 2

during S phase

Question 3

what elements does DNA contain?

Answer 3

C, H, O, N, and P

Question 4

transformation

Answer 4

addition of DNA from one strand of bacterium could genetically transform another strand

Question 5

bacteriophage

Answer 5

viruses that infect bacteria

Question 6

transgenic

Answer 6

fertilised egg can develop into a new multicellular organism through mitosis

Question 7

what is the structure of DNA?

Answer 7

helical with antiparallel strands

Question 8

base pairs

Answer 8

A-T

C-G

Question 9

purines

Answer 9

A and G

Question 10

pyrimidines

Answer 10

T and C

Question 11

what holds together the DNA chains?

Answer 11

hydrogen bonding between bases

Question 12

what is the orientation of the DNA double helix?

Answer 12

right handed

Question 13

Z-DNA

Answer 13

unstable DNA that forms a left handed helix

Question 14

storage of genetic information

Answer 14

DNA can encode and store a lot of information in its nucleotides

Question 15

precise replication during the cell division cycle

Answer 15

replication can be accomplished by complementary base pairing

Question 16

susceptibility to mutations

Answer 16

DNA structure allows for potential stable changes in genetic material

Question 17

expression of the coded information as phenotypes

Answer 17

varied enzymes and proteins encoded by DNA determine phenotypes

Question 18

semiconservative replication

Answer 18

each strand of parental DNA acts as a template for a new strand

Question 19

what are the steps for DNA replication?

Answer 19

DNA double helix is unwound, and then nucleotides form complementary base pairs with template DNA

Question 20

what direction does replication read the DNA in?

Answer 20

3’-5’

Question 21

in what direction is the new strand of DNA generated?

Answer 21

5’-3’

Question 22

dNTPs

Answer 22

raw materials for DNA synthesis

Question 23

DNA polymerase

Answer 23

catalyses the addition of nucleotides

Question 24

origin of replication

Answer 24

where the pre-replication complex binds

Question 25

replication forks

Answer 25

the different directions of DNA replication

Question 26

DNA helicase

Answer 26

catalyses the opening of each fork

Question 27

primer

Answer 27

a short starter strand for new nucleotides to link to

Question 28

primase

Answer 28

an enzyme that synthesises nucleotides one at a time

Question 29

leading strand

Answer 29

newly synthesised growing strand

Question 30

lagging strand

Answer 30

grows in the direction away from the replication fork

Question 31

Okazaki fragments

Answer 31

stretches of new DNA that are relatively short and discontinuous

Question 32

DNA ligase

Answer 32

catalyses the formation of the bond between adjacent Okazaki fragments

Question 33

what does it mean for DNA polymerase to be processive?

Answer 33

catalyses many sequential polymerisation reactions each time it binds to a DNA molecule

Question 34

telomeres

Answer 34

repetitive sequences at the ends of the chromosomes to prevent chromosomes from joining

Question 35

what is the telomere sequence in humans?

Answer 35

TTAGGG

Question 36

telomerase

Answer 36

catalyses the addition of any lost telomeric sequences

Question 37

proofreading

Answer 37

occurs right after DNA polymerase inserts a nucleotide, removes the improperly introduced nucleotide and tries again

Question 38

mismatch repair

Answer 38

occurs after DNA has been replicated, removes portion of DNA containing the incorrect nucleotide and inserts the correct sequence

Question 39

polymerase chain reaction

Answer 39

allows researchers to make multiple copies of short DNA sequences

Question 40

somatic mutation

Answer 40

occur in somatic cells and are passed on to daughter cells during mitosis

Question 41

germline mutations

Answer 41

occur in the germ line, affects gametes

Question 42

silent mutations

Answer 42

do not affect gene function

Question 43

loss-of-function mutations

Answer 43

result in either the loss of expression of a gene or in the production of a nonfunctional protein or RNA

Question 44

gain-of-function mutations

Answer 44

lead to a protein with an altered function that usually shows dominant inheritance

Question 45

conditional mutations

Answer 45

cause phenotypes only under certain restrictive conditions

Question 46

point mutation

Answer 46

addition or subtraction of a single nucleotide base, or the substitution of one base for another

Question 47

mutagens

Answer 47

substances that cause mutations such as radiation or certain chemicals

Question 48

chromosomal mutations

Answer 48

whole chromosomes can break and rejoin, disrupting the gene sequence

Question 49

deletions

Answer 49

removal of part of the genetic material

Question 50

duplications

Answer 50

homologous chromosomes broke at different positions and then reconnected to the wrong partners

Question 51

inversions

Answer 51

segment of DNA may be removed and reinserted into the same location, but flipped over

Question 52

translocations

Answer 52

segments of chromosomes break off and become joined to different chromosomes

Question 53

spontaneous mutations

Answer 53

permanent changes int he genetic material that occur without may outside influence

Question 54

induced mutations

Answer 54

some agent from outside the cell causes a permanent change in the DNA sequence

Question 55

where do mutations occur most often?

Answer 55

where cytosine has been methylated to 5-methylcytosine

Question 56

benefits of mutations

Answer 56

provides genetic diversity that makes natural selection possible

Question 57

costs of mutations

Answer 57

may result in loss of function of genes or DNA sequences needed for survival