Mutation

Question 1

rare alleles are termed

Answer 1

mutations

Question 2

an organisms containing rare alleles are termed

Answer 2

mutants- often non functional proteins

Question 3

the normal allele organism are termed

Answer 3

wild types- normal proteins

Question 4

mechanisms of preventing mutation

Answer 4

-proofreading DNA polymerases -post replication mismatch repair- Muts and MutL -DNA repair by homologous recombination -cell cycle checkpoints

Question 5

environmental factors which cause mutations

Answer 5

radiation chemical mutagens

Question 6

replication slippages

Answer 6

can generate Short tandem repeats or minisattelites variation e.g. additions

Question 7

variation in a single gene is

Answer 7

necessary and sufficient too cause disease - more than 1000 genes known in humans

Question 8

mutations and mendelian disorders

Answer 8

mendelian disorders are controlled by a single locus in an inheritance pattern- therefore a mutation in a single gene can cause disease

Question 9

example of a mutated single gene causing disease

Answer 9

cystic fibrosis-recessive sickle cell anaemia -recessive albinism -recessive Huntingtons- dominant Haemophilia A- x linked

Question 10

in diploids mutations are normally..

Answer 10

recessive, this is why mutations are lethal in haploid or homozygous organisms

Question 11

mutations and selections

Answer 11

Ledeerbergs experiment in 1952 showed that mutations occur before selection, therefore selection does not cause mutation

Question 12

transition mutations

Answer 12

a point mutation that changes a purine nucleotide to another purine (A G) or a pyrimidine nucleotide to another pyrimidine ( T C)

Question 13

purine nucleotides

Answer 13

A G

Question 14

pyrimidine nucleotides

Answer 14

C T

Question 15

pyrimidine nucleotides

Answer 15

C T

Question 16

Transversion mutation

Answer 16

substitution of a two ring purine for a one ring pyrimidine or vice versa e.g. A substituted for T e.g. G substituted for C

Question 17

three types of chemical mutagens

Answer 17

1) intercalating agents 2) base analogues 3) base modifying agents

Question 18

intercalating agents

Answer 18

insert between able pairs since they have a similar shape to nucleotides and cause a frameshift mutation– planar molecules e.g. proflavin

Question 19

base analogues

Answer 19

incorporated into DNA in place of normal base= mis -pair base

Question 20

base modifying agents

Answer 20

covalently alter a base causing is to mispair e.g. if an amine group is removed from cytosine it is transformed to uracil

Question 21

UV can lead to

Answer 21

point mutations

Question 22

point mutations are caused by

Answer 22

UV

Question 23

e.g. two seperate thymine on a dna backbone can be transformed to

Answer 23

a photodimer

Question 24

UV causes two thymine to become

Answer 24

a photodimer on a backbone

Question 25

photolyase and white light causes

Answer 25

photodimer to become 2 thymine again

Question 26

photodimer to become 2 thymine again

Answer 26

photolyase and white light causes

Question 27

photolayse

Answer 27

Photolyases (EC 4.1.99.3) are DNA repair enzymes that repair damage caused by exposure to ultraviolet light. This enzyme requires visible light, preferentially from the violet/blue end of the spectrum, and the mechanism known as photo reactivation.§

Question 28

base modifying agents

Answer 28

covalently alter a base causing it to mispair

Question 29

what covalently alter a base causing it to mispair

Answer 29

base modifying agent

Question 30

delaminating agents

Answer 30

remove amino groups

Question 31

hydroxylating agents

Answer 31

add hydroxyl groups

Question 32

alkylating agents

Answer 32

add alkyl groups

Question 33

Temp sensitive mutation

Answer 33

e.g. mutant protein is less stable at non-permissive temp -very useful for studying essential cell function e.g. yeast mutants

Question 34

example of selection using temp and mutagenised cells

Answer 34

mutagenised cells proliferate at 23 degrees - colonies are replicated onto two identical plates and incubated at 2 diff temps 23- mutant cells proliferate and form a colony at the permissive temp 36- mutant cells fait to proliferate and from a colony at the non permissive temp selection is often used by geneticists to isolate rare mutants- especially useful with microbes, after mutagenesis

Question 35

example of selection using temp and mutagenised cells

Answer 35

mutagenised cells proliferate at 23 degrees - colonies are replicated onto two identical plates and incubated at 2 diff temps 23- mutant cells proliferate and form a colony at the permissive temp 36- mutant cells fait to proliferate and from a colony at the non permissive temp selection is often used by geneticists to isolate rare mutants- especially useful with microbes, after mutagenesis

Question 36

frameshift mutations are likely to

Answer 36

give a non-functional protein

Question 37

what can be used to study essential function

Answer 37

conditional lethal mutant

Question 38

mutation is random but..

Answer 38

its frequency may be increased by environmental. genetic factors

Question 39

conditional lethal mutants

Answer 39

Conditional lethal mutations are changes in the sequence of genetic material, which kill the organism, but only when it faces certain environmental conditions; under other conditions, the organism can survive and grow. Such mutations are useful genetic markers for a variety of essential genes.

Question 40

replication slippage can involve …

Answer 40

slippage on new strand

or

template strand

Question 41

slippage on new strand

Answer 41

• newly synthesised strand slips
• causes an extra nucleotide to be copied on the new strand

Question 42

slippage on the tempate strand

Answer 42

slippage on the template strand results in the new strand havingone nucleotide ommitted