DNA damage and mutations

Question 1

What is a mutation?

Answer 1

Random event A heritable change in genetic material not due to genetic recombination. They are the ultimate source of differences among species. BUT most genetic variations are due to genetic recombination and sex (meiosis and independent assortment of pat and mat chromosomes)/

Question 2

What causes heritable disease?

Answer 2

Mutations.

Question 3

Before mutation, what is the normal sequence called?

Answer 3

Wild type. (non-diseased, usually hard to choose due to variation in population so usually arbitrarily chosen).

Question 4

What are the 2 broad types of mutation?

Answer 4

1. Point (minor changes in DNA seq involving one or few nucleotides)
2. Rearrangements ( extensive chromosomal alterations involving hundreds of base pairs or even whole chromosomes)

Question 5

What are the different ways in which mutations can be classified based on?

Answer 5

origin, cell type, expression, effect of function, molecular change (change at the DNA level) and effect on translation..

Question 6

What is a spontaneous mutation?

Answer 6

Occurs in absence of known mutagen, usually due to errors in DNA replication or due to the effect of compounds normally
present in cell (Reactive O species).

Question 7

What is an induced mutation?

Answer 7

occurs in presence of known mutagen.

Question 8

What is a mutagen?

Answer 8

Chemical or physical agent that increases rate of mutagenesis. There are thousands of natural and synthetic chemicals that can damage DNA. Physical mutagens include ionising raditation and UV.

Question 9

What is a somatic mutation?

Answer 9

Occurs in nonreproductive cells. Are not passed onto next generation. Can lead to disease (like cancer) and cause ageing).

Question 10

What is a mutation that occurs in reproductive cells?

Answer 10

Germ-line mutation, will be passed onto next generation and are ultimately responsible for genetic variation.

Question 11

What is an unconditional mutation?

Answer 11

Expressed at all times.

Question 12

What is a conditional mutation?

Answer 12

only expressed under certain conditions. e.g. temperature sensitive

Question 13

Give an example of a temperature sensitive mutation.

Answer 13

Cat: tyrosine hot goes white fur, cold - melanin so brown.

Question 14

What is the name for a loss of function mutation?

Answer 14

null or knockout.

Question 15

What is the name for a mutation that reduces normal function?

Answer 15

leaky

Question 16

What is the name for a gain of function mutation?

Answer 16

ectopic expression, expressed at incorrect time or inappropriate cell types.

Question 17

What are the 2 types of base substitution?

Answer 17

Transistion: pyr to pyr or pur to pur.
Transversion: Pyr to pur or pur to pyr

Question 18

What since base mutations cause frame shifts?

Answer 18

insertion or deletion.

Question 19

What is a mutation that causes a change in the amino acid encoded?

Answer 19

Missense.

Question 20

What is a mutation that causes a premature termination?

Answer 20

nonsense.

Question 21

What is a mutation calledthat does not effect the encoded AA?

Answer 21

silent.

Question 22

What is a mutation called that changes the AA to an AA with similar function?

Answer 22

Neutral.

Question 23

What is a frameshift mutation?

Answer 23

Shifts triplet reading of codons out of correct phase.

Question 24

What is phenyketonuria?

Answer 24

missense mutation in phenylalanine hydroxylase gene. C to T, Arg to Trp. Autosomal recessive trait, sufferers must avoid phenylalanine in diet.