Nature and impact of mutations

Question 1

Define: mutation

Answer 1

change to nucleotide sequence of DNA

Question 2

where do mutations most commonly occur

Answer 2

anywhere but mainly in non coding regions

Question 3

in exons, what fraction of genes are polymorphic?

Answer 3

1/3

Question 4

inherited mutations

• cell it occurs in
• where subsequent mutations will be found
• can it be passed down
• effects

Answer 4

germline cells (diploid cells which give rise to gametes)
in all nucleated cells that come from zygote
yes
causes single gene disorders (cystic fibrosis), often a risk factor for multifactor gene disorders

Question 5

non inherited mutations

• cell it occurs in
• where subsequent mutations will be found
• can it be passed down
• effects

Answer 5

occurs in somatic cellls
mutations occur in affected the cell and the cells it gives rise to
cant be passed down - not a gamete
can lead to multifactorial diseases

Question 6

two main classes of mutations

Answer 6

point mutations and large scale mutations

Question 7

2 types of point mutations, and their subtypes

Answer 7

frameshift 
-deletion
-insertion
substitution
-nonsense (stop codon)
-silent (same codon)
-missense (different codon)

Question 8

how do frameshift mutations arise? (AP)

Answer 8

depurination of adenine - base hydrolysed. basically adenine ceases to exist in the DNA; when this is replicated there will be no T

Question 9

how to substitution mutations occur (NICU)

Answer 9

deamination of C turns it to U. when this strand is replicated, A will pair with it instead of G
–>unaffected strand replicates as normal

Question 10

4 types of large scale mutations?

Answer 10

• deletion
• inversion
• translocation (2 parts swap on NON HOMOLOGOUS CHROMOSOMES)
• deletion and duplication (2 parts swap on HOMOLOGOUS CHROMOSoES)

Question 11

describe duchene and becker muscular dystrophy

Answer 11

x linked - boys
79 exon dystrophin gene affected –> causing large scale deletion.
deleted segment is one bp longer in duchenne than becker; causes frameshift in duchenne and NOT becker, hence duchenne is more severe.

Question 12

what can happen when T is in its tautomeric form

Answer 12

binds with G instead of A. replication can lead to substituion

Question 13

causes of mutations

Answer 13

transposons and retroviruses
spontaneous mutations
induced mutations

Question 14

examples of induced mutations?

Answer 14

chemicals

radiation - UV, free radicals