Chapter 14

Question 1

Explain the end replication problem

Answer 1

-the lagging strand requires mRNA primers. when the primers are removed the new daughter strand is shortened by about 100 nucleotides

Question 2

why is the end replication problem important

Answer 2

without it, cells would lose control of their cell cycle

Question 3

what is the solution to the end replication problem

Answer 3

• in somatic cells telomerase is off, but in germ cells it is on because germ cells need enough DNA to replicate
• telomerase contains an RNA template that allows the template strand to be lengthened with telomerase repeats
• telomerase adds the RNA template to the parent strand then uses normal mechanisms to extend the length of the daughter strand to what it should’ve been

Question 4

what is genetic variation

Answer 4

genetic differences that exist among individuals in a population at a particular point in time

Question 5

what is an example of a harmful mutation and what happens in the mutation

Answer 5

emphysema:

• Alpha 1AT gene codes an enzyme that inhibits breakdown of elastase
• normal lung elasticity is maintained by a balance between elastin production and destruction
• in emphysema the alpha 1AT activity is reduced by cigarette smoke so it results in excessive destruction of elastin, loss of lung elasticity and emphysema
• can happen through a mutation in the gene encoding Alpha 1AT. mutant allele is called PiZ, must be homozygous

Question 6

how can a mutation be neutral

Answer 6

-it is often found on non-coding DNA regions

Question 7

what is an example of a beneficial mutation and what happens in the mutation

Answer 7

• the env region in the HIV genome codes a surface glycoprotein
• for HIV to invade a t-cell it must interact with a CD4 receptor and a CCR5 co-receptor
• Delta32 mutant CCR5 allele leads to reduced ability of HIV to infect cell

Question 8

what matters most for germ line mutations?

Answer 8

the rate of mutation per organismal generation matters most

Question 9

why are germ line mutations important to evolutionary processes

Answer 9

because through transmission between generations they may become present in many individuals

Question 10

what matters most for somatic mutations?

Answer 10

the rate of mutation per cycle of DNA replication

Question 11

what happens in the multiple mutation model of cancer progression

Answer 11

first the APC gene (tumor suppressor) is mutated then RAS gene (proto oncogene) then the p53 gene (tumor suppressor)

Question 12

what is the APC gene

Answer 12

a tumor suppressor

Question 13

what Is the RAS gene

Answer 13

proto oncogene

Question 14

what is the p53 gene

Answer 14

tumor suppressor

Question 15

what is replica plating

Answer 15

allows a researcher to isolate a pure culture of antibiotic resistant bacteria even though the original bacteria had never been exposed to the antibiotic

Question 16

what does replica plating support

Answer 16

that mutations are random

Question 17

what does DNA polymerase do

Answer 17

proofreads

Question 18

what do mismatch repair enzymes do

Answer 18

fix anything DNA polymerase missed

Question 19

what happens small scale when mutations are not repaired

Answer 19

nucleotide substitution or point mutation or frameshift

Question 20

what are the different kinds of point mutations

Answer 20

• synonymous (silent) mutations
• nonsynonymous (missense) mutations
• nonsense mutations

Question 21

what happens large scale when mutations are not repaired

Answer 21

insertion or deletion

Question 22

what is a point mutation

Answer 22

• most common

- one nucleotide change

Question 23

what is a synonymous mutation

Answer 23

a nucleotide substitution does not change the amino acid

Question 24

what is a non synonymous mutation

Answer 24

changes the amino acid

Question 25

what is a nonsense mutation

Answer 25

mutation that creates a stop codon

Question 26

what kind of a mutation happens in sickle cell anemia

Answer 26

point mutation

Question 27

what kind of mutation happens in cystic fibrosis

Answer 27

deletion of 3 nucleotides = 1 amino acid

Question 28

what happens in a frameshift mutation

Answer 28

insertion or deletion of 1 or 2 bases results in disruption of the reading frame

Question 29

what does DNA ligase do

Answer 29

seals break in sugar phosphate backbone

Question 30

what happens in base excision repair

Answer 30

incorrect base and its sugar excised from the strand then replaced

Question 31

what happens in nucleotide excision repair

Answer 31

-recognizes multiple mismatched bases in a region

Question 32

what happens in mismatch repair

Answer 32

single misfired base repaired by removing and replacing a DNA segment

Question 33

what enzymes repair DNA segments

Answer 33

DNA polymerase fills the gap and DNA ligase seals the strand

Question 34

how do mutations occur

Answer 34

spontaneously or through mutagens

Question 35

what mutagens cause mutations

Answer 35

x-rays, UV light, and chemicals

Question 36

what do X-rays do to DNA

Answer 36

causes break in sugar phosphate backbone

Question 37

what does UV light do to DNA

Answer 37

causes adjacent pyrimidines to cross link

Question 38

what do chemicals do to DNA

Answer 38

bleach and H2O2 can cause loss of a base and tobacco can add bulky side groups to bases

Question 39

why are mutations tolerable in the human genome

Answer 39

• most are repaired right away
• mutation rate is low
• mutations are neutral
• most happen in non-coding DNA