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Flashcards in Mutation Deck (42):
1

rare alleles are termed

mutations

2

an organisms containing rare alleles are termed

mutants- often non functional proteins

3

the normal allele organism are termed

wild types- normal proteins

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mechanisms of preventing mutation

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

5

environmental factors which cause mutations

radiation chemical mutagens

6

replication slippages

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

7

variation in a single gene is

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

8

mutations and mendelian disorders

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

9

example of a mutated single gene causing disease

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

10

in diploids mutations are normally..

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

11

mutations and selections

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

12

transition mutations

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

13

purine nucleotides

A G

14

pyrimidine nucleotides

C T

15

pyrimidine nucleotides

C T

16

Transversion mutation

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

17

three types of chemical mutagens

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

18

intercalating agents

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

19

base analogues

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

20

base modifying agents

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

21

UV can lead to

point mutations

22

point mutations are caused by

UV

23

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

a photodimer

24

UV causes two thymine to become

a photodimer on a backbone

25

photolyase and white light causes

photodimer to become 2 thymine again

26

photodimer to become 2 thymine again

photolyase and white light causes

27

photolayse

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.§

28

base modifying agents

covalently alter a base causing it to mispair

29

what covalently alter a base causing it to mispair

base modifying agent

30

delaminating agents

remove amino groups

31

hydroxylating agents

add hydroxyl groups

32

alkylating agents

add alkyl groups

33

Temp sensitive mutation

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

34

example of selection using temp and mutagenised cells

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

35

example of selection using temp and mutagenised cells

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

36

frameshift mutations are likely to

give a non-functional protein

37

what can be used to study essential function

conditional lethal mutant

38

mutation is random but..

its frequency may be increased by environmental. genetic factors

39

conditional lethal mutants

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.

40

replication slippage can involve ...

slippage on new strand 

or

template strand

41

slippage on new strand

-newly synthesised strand slips 

-causes an extra nucleotide to be copied on  the new strand

42

slippage on the tempate strand

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