CH 14 Mutation and DNA Repair Reading Guide

Question 1

Does a new mutation occur every time a cell

divides?

Answer 1

No there is a 10^(-10) percent chance

Question 2

Do you think that any new mutations have accumulated in the cells within your body since the time your were first conceived

Answer 2

Yes

Question 3

How can the human genome tolerate ~30 new mutations in every generation?

Answer 3

Because many of the sections of DNA subject to mutation are non functioning section so they play no important role

Question 4

What’s the difference between somatic cells and germ-line cells?

Answer 4

Somatic cells are all other cells of the body that are not associated with reproduction
Germ cells are the reproductive cells

Question 5

Give examples of genes that when mutated in somatic cells might give rise to cancer

Answer 5

APC, Ras and p53 genes can give rise to malignant colon cancer

Question 6

Why

do you think cancer is a lot more common in old people than in young?

Answer 6

Because they have undergone much more cell replications increasing their likely hood for gene to be mutated

Question 7

Which type (somatic or germ line mutations)
can change the course of evolution?

Answer 7

Germ line mutations as they are passed down through generations

Question 8

What two hypothesis were proposed by the Lederbergs?

Answer 8

Mutations occur randomly with respect to the needs of an organism
The environment induces mutation (in this case antibiotic resistance)

Question 9

In what sense is a growth medium that contains an antibiotic agent ‘selective’? In what
sense is a growth medium that contains only nutrients, nothing toxic, ‘nonselective’?

Answer 9

Because it allows for only antibiotic resistant bacteria to survive (selects them)
Allows for all type of bacteria to survive

Question 10

Did the selection on medium containing an antibiotic produce / trigger mutations in
bacteria that allowed the cells to survive in the presence of the antibiotic? Explain.

Answer 10

Yes.

Mutations (antibiotic resistance) can arise in the absence of antibiotic.

Question 11

Does the environment direct the formation of specific mutations that allow cells to
survive better? Explain?

Answer 11

No

Mutations are random and not directed by the environment

Question 12

Does DNA polymerase ever make mistakes
during DNA replication? If so, does it have the ability to detect and repair its own
mistakes? Is DNA polymerase 100% reliable?

Answer 12

Yes
Yes it has a proof reading function
Not 100% reliable

Question 13

Define synonymous mutation

Answer 13

Changes in the base pairs that do not result in a change to the amino acid sequence

Question 14

Define non synonymous mutation

Answer 14

Point mutation that causes an amino acid replacement

Question 15

Mutation of which human gene give rise to sickle cell anemia disease? Is this disease
caused by a synonymous or nonsynonymous mutation?

Answer 15

Beta globin gene

Considered a non synonymous mutation. Changes what should be a Glu to a Val amino acid

Question 16

Define a nonsense mutation

Answer 16

A nonsense mutation changes an amino acid to a stop codon therefore ending translation resulting in a shortened unstable protein

Question 17

would a nonsense mutation have a more severe effect if it occurred
near the middle of a coding sequence, or close to the end of the last exon?

Answer 17

Yes more severe closer to the middle of the coding sequence

Question 18

How is a frameshift mutation different from an insertion/deletion of three nucleotides
within a reading frame?

Answer 18

It usually involves the insertion of a single nucleotide that evokes a major shift in the reading frame. Making an entire sequence illegible

Question 19

What is the normal ‘dosage’ of any given gene (residing on an autosome) in the
genome? How does duplications and deletions result in deviations from normal gene
dosage?

Answer 19

Normal dosage refers to the number of copies of each gene. Every organisms is sensitive to changes in dosage
Duplications makes repeated segments on the chromosome while deletions remove segments

Question 20

Why are small duplications/deletions better tolerated than large ones?

Answer 20

Large duplications and deletions are not compatible with life

Question 21

What type of damage can X-rays do to DNA?

Answer 21

Break the sugar-phosphate backbone of DNA

Question 22

What type of damage can UV radiation do to DNA?

Answer 22

Causes cross-links between adjacent pyrimidine bases, especially thymine, resulting in thymine dimers

Question 23

Spontaneous hydrolysis of a purine base from carbon 1 of the deoxyribose sugar: is this
a common occurrence?

Answer 23

Yes.

13,000 purines lost per human cell per day

Question 24

Chemical modification of a base, e.g. replacing an -NH2 group with a double bonded
oxygen: what is the consequence?

Answer 24

Spontaneous damage to the bases

Question 25

Addition of a bulky side group to a base (e.g. by compounds in tobacco smoke),
consequence?

Answer 25

Hinder proper base pairing and cause deletion and insertions of nucleotides