Mutation

Question 1

polymorphism

Answer 1

any genetic difference among individuals that is present in multiple individuals in a population

Question 2

somatic mutation

Answer 2

occur in nonreproductive cells
passed via mitosis

Question 3

germ-line mutations

Answer 3

occur in cells that give rise to gametes
meiosis transmission
heritable
raw material for evolution

Question 4

sequential somatic mutations in cancer

Answer 4

series of mutations occur in the descendants of a single somatic cell. The first mutation occurs in a gene called APC, which normally inhibits abnormal cellular growth. The mutant APC cells begin to proliferate, but slowly.
Because mutations occur randomly and independently of existing mutations, there is a chance that one of the descendant APC cells will undergo a mutation in a gene called Ras. When a Ras mutation happens in a cell already carrying APC, the mutant cells divide even faster than before, but are still not malignant. But as they proliferate, there is a chance that one of the descendant cells will undergo a mutation in the gene p53.
This third mutation allow cells with further DNA damage to survive and divide extremely rapidly. And the cell lineage becomes malignant colon cancer

Question 5

genetic risk factor

Answer 5

mutation that increases the risk of disease in an individual

Question 6

multiple-mutation model for cancer development

Answer 6

Most human cancers require more than the overactivation of one oncogene or the inactivation of a single tumour suppressor

Question 7

mutation rates

Answer 7

number of new mutations per genome per generation is not especially variable
mutation rate per genome per replication constant
higher for species with smaller genomes
greater rate of mutation in somatic cells

Question 8

male mutation bias

Answer 8

mutation rate is higher in the male germline (sperm cells) compared to the female germline (egg cells). spermatogenesis throughout life time
most new mutations originate in males
older fathers-mutation rate increasing

Question 9

indels

Answer 9

cant tell which sequence had an insertion/deletion

Question 10

wobble base pairing

Answer 10

occurs with point mutations (substitutions)

Question 11

transition

Answer 11

substitution of a purine for a purine or of a pyrimidine for a pyrimidine
small change in structural difference

Question 12

pyrimidines

Answer 12

thymine and cytosine

Question 13

purines

Answer 13

adenine and guanine

Question 14

transversions

Answer 14

substitution of a pyrimidine for a purine or vice versa

Question 15

transition:transversion

Answer 15

transitions more common
2:1
rate

Question 16

copy number variation

Answer 16

form of genetic variation
number of copies of a particular segment of DNA varies between individual.
duplicated/deleted regions that include one or more genes
CNVs in coding regions cause tandem copies

Question 17

tandem repeats

Answer 17

type of CNV
repeated sequences of DNA where the number of copies vary among individuals
the number of copies variation generates different alleles
DNA fingerprinting

Question 18

how X rays cause mutation

Answer 18

cause breaks in the sugar-phosphate backbone

Question 19

how UV light causes mutation

Answer 19

causes adjacent pyrimidines to cross -link forming thymine dimers which blocks replication

Question 20

highly reactive chemicals and mutation

Answer 20

tend to be mutagenic as they can add bulky side groups to the bases
hinders proper base pairing

Question 21

bleach/hydrogen peroxide and mutation

Answer 21

can cause loss of a base
gaps

Question 22

tobacco smoke and mutation

Answer 22

adds bulky side groups to bases
improper base pairing

Question 23

pyrimidine dimer

Answer 23

two thymine bases
block replication

Question 24

SOS system bacteria

Answer 24

by pass replication block with a mutation-prone pathway

Question 25

strand slippage, insertions

Answer 25

newly synthesised strand loops out resulting in the addition of a nucleotide on the new strand

Question 26

strand slippage, deletions

Answer 26

template strand loops out resulting in the omission of one nucleotide on the new strand

Question 27

repeated sequences have a -----rate of strand slippage

Answer 27

higher

Question 28

unequal crossing over

Answer 28

if homologous chromosomes misalign during crossing over, one cross over product contains an insertion and the other a deletion also caused by repeated sequences

Question 29

repeat expansions

Answer 29

type of insertion increase in number of copies of group of nucleotides beyond normal range can be caused by repetitive sequences

Question 30

fragile-X chromosome

Answer 30

constriction on long arm CGG repeat expansion strand slippage causes some individuals to have too many copes of it more common in males

Question 31

repeat expansion mechanism

Answer 31

DNA molecule normally has x copies of a repeat (eg CAG) the 2 strands separate and replicate and in the course of replication, a hairpin forms on the newly synthesised strand (strand slippage) part of template strand is replicated twice; increasing number of repeats on the newly synthesised strand the newly synthesised strand acts as template next round so the resulting DNA molecule has >x copies of the (CAG) repeat

Question 32

transposable elements/transposons

Answer 32

DNA sequences that can move from one position to another in the genome can insert into a gene and disrupt its function

Question 33

types of DNA damage repair

Answer 33

post-replication mismatch repair base excision repair nucleotide excision repair

Question 34

DNA ligase

Answer 34

seals breaks in the sugar-phosphate backbone uses energy from ATP to join the 3' OH to 5' phosphate

Question 35

post-replication mismatch repair

Answer 35

a single mispaired base is repaired by removing and replacing a DNA segment.

Question 36

base excision repair

Answer 36

the incorrect base and its sugar are excised from the strand then replaced

Question 37

nucleotide excision repair

Answer 37

recognises multiple mismatched bases in a region

Question 38

mismatch repair mechanism

Answer 38

mismatched bases recognised and a repair enzyme breaks the backbone downstream. another enzyme removes successive nucleotides, including the mismatched one. DNA polymerase adds the missing bases, DNA ligase joins backbones

Question 39

base excision repair mechanism

Answer 39

enzyme recognises incorrect base and binds with the site, cleaving the base from the deoxyribose sugar. a different enzyme AP endonuclease recognises the site with missing base and binds with DNA to cleave the backbone in 2 places to free the sugar. leaves a gap. other enzymes bind with the site of the gap and insert a nucleotide with proper base pairing

Question 40

nucleotide excision repair mechanism

Answer 40

one or more damaged bases signal repair process, enzymes cleave DNA backbone at these sites. region with damaged bases removed, gap filled by new DNA synthesis

Question 41

forward mutation

Answer 41

wild type to mutant type

Question 42

reverse mutation

Answer 42

mutant type to wild type

Question 43

silent mutation

Answer 43

doesnt change amino acid sequence codon to synonymous codon

Question 44

missense mutation

Answer 44

amino acid to different amino acid

Question 45

nonsense mutation

Answer 45

sense codon to nonsense (stop) codon (introduction of premature stop codon) causes truncation where nearly all truncated proteins are nonfunctional and unstable

Question 46

deleterious mutations

Answer 46

decrease fitness most extreme are lethal mutations

Question 47

advantageous mutations

Answer 47

increase fitness

Question 48

neutral mutations

Answer 48

no effect on fitness

Question 49

epistasis

Answer 49

mutations effect in fitness also dependent on genetic background (other genes)

Question 50

loss-of-function mutations

Answer 50

common normally recessive

Question 51

gain of function mutations

Answer 51

uncommon normally dominant

Question 52

conditional mutation

Answer 52

effect of mutation depends on something else, eg environmental condition

Question 53

suppressor mutations

Answer 53

a mutation that hides or suppresses effects of another can be inter or intragenic