Chapter 14

Question 1

What is a mutation?

Answer 1

-a heritable change in the genetic material
-passed on via meiosis of sperm and egg
occurs in S phase DNA replication or unprepared DNA damage.

Question 2

What causes DNA damage?

Answer 2

radiation
reactive molecules produced in metabolism
chemicals in the environment.

Question 3

What is the most common form of a mutation?

Answer 3

the substitution of one nucleotide pair for a different nucleotide pair, but still relatively rare, post mutations.

Question 4

Why does RNA have a higher mutation rate than DNA?

Answer 4

RNA is a less stable molecule than DNA and the replication of RNA lacks a proofreading (backtracking) function.

Question 5

What is the average substitution error number in a human?

Answer 5

about 1 nucleotide per 10 billion nucleotides replicated

Question 6

Why do female gametes suffer less from replication derived mutations than male gametes do?

Answer 6

females are born with eggs already made where males are constantly producing sperm

Question 7

Why are woman eggs “bad” as they get older?

Answer 7

when ovulation occurs the egg is in meiosis I and once the egg is fertilized it enters meiosis II, as a woman ages the mitotic spindle oxidizes causing problems with separation

Question 8

What are germ and somatic cells?

Answer 8

germ cells: haploid gametes and diploid cells

somatic cells: non reproductive cell

Question 9

is the rate of mutation per nucleotide greater in somatic or germ cells?

Answer 9

somatic cells.

Question 10

why do humans have such a large rate of mutation per genome per generation?

Answer 10

humans have a large genome and undergo many cell divisions per generation

Question 11

what is the number of nucleotide substitution mutations per genome in one generation?

Answer 11

30 or 60 per diploid zygote.

Question 12

what percent of zygote mutations have come from the father and why?

Answer 12

80% because at 30 males have gone through 400 cycles of DNA replication and cell division before meiosis compared to woman who have only had 30.

Question 13

Why can such a large number of mutations occur in humans?

Answer 13

a very small proportion of the genome is actually involved in regulating gene expression or coding for gene products

Question 14

what to somatic mutations and germ mutations effect?

Answer 14

somatic- only the individual in which they occur

germ- transmitted to future generations since they occur in reproductive cells.

Question 15

what mutation explains genetic diversity

Answer 15

germ line mutations

Question 16

What factors give rise to cell growth and preventing cell growth?

Answer 16

promotes cell growth- proto-oncogenes, cyclin-CDK

tumor suppressor- p53, checkpoint proteins

Question 17

how many mutations must occur before cancer?

Answer 17

3 successive mutations of the same cell.

Question 18

What is a genetic risk factor?

Answer 18

A mutation that increases the risk of diseases in an individual. doesn’t make you have the disease but the likelihood of the disease happing increases

Question 19

What are the major risk factors in
colon cancer
breast cancer

Answer 19

colon cancer- APC, Ras, and p53

Breast Cancer- BRCA1 and BRCA2 genes

Question 20

What were the lederbergs trying to investigate with their experiment?

Answer 20

1. mutations occur randomly in bacterial populations and over time become more common in the presence of an antibiotic
2. the antibiotic (environment) induces or direct antibiotic resistance.

Question 21

in what sense is a growth medium that contains an antibiotic selective?

Answer 21

because it selects for a particular attribute or element, in this case antibiotic resistant cells

Question 22

in what sense is a growth that contains only nutrients, nothing toxic non-selective?

Answer 22

because all cells were able to grow and form colonies

Question 23

what are point mutations?

Answer 23

changes in a single nucleotide.

Question 24

How does DNA polymerase correct mistakes?

Answer 24

a proofreading function of DNA polymerase during replication, acts to remove an incorrect nucleotide from the 3’ end of the growing DNA strand.

Question 25

What is a situation where the DNA polymerase proofreading wouldn’t work?

Answer 25

when DNA polymerase mistakenly adds a G instead of a T across from an A then the result is a G-T mismatch I. the double stranded DNA.

Question 26

what are the possible nucleotide mutation names and meanings?

Answer 26

Nonmutant- normal
Synonymous mutation- a nucleotide submission that changes a nitrogenous base but does not change the amino acid (differ in third position)
Nonsynonymous mutation- A nucleotide substitution that changes the amino acid

Question 27

Mutation of which human gene gives rise to sickle cell anemia?

Answer 27

inheritance of 2 mutant Glu-Val B-globin genes. non synonymous.

Question 28

what is a nonsense mutation?

Answer 28

creates a stop codon terminating the translation. UAG codon, non functional and destroyed.

Question 29

A chromosome mutation can effect how many nucleotides?

Answer 29

thousands to millions of nucleotides.

Question 30

Duplications, deletions and translocations are a result of what?

Answer 30

improper/ uneven crossing over during prophase I of meiosis.
duplication and deletion- uneven crossing over of homologs duplication on 1 homolog and deletion on the other.
translocations- cross overs between non-homologous chromosomes where a segment from on chromosome is transferred to the other.

Question 31

duplications or deletions affecting. only a few genes are usually well tolerated when are they not?

Answer 31

some genes are dosage sensitive; important to have exactly 2 copies (maternal and paternal)

Question 32

DNA damage can effect both

Answer 32

the DNA backbone and its bases

Question 33

DNA damage should be caught by what checkpoint?

Answer 33

G1/S checkpoint.

Question 34

what are 5 DNA damage cases? what causes them?

Answer 34

1. single stranded break in DNA backbone- radiation
2. cross-linked thymine bases- UV light
3. missing base- most common, problem w hydrolyzing
4. bulky group attached to a base- smoke
5. double stranded break in backbone- radiation

Question 35

What types of enzymes would be able to repair breaks and gaps in the DNA backbone?

Answer 35

ligases. specialize outside of Phase in single strand and double strand breaks