L23 Mutations

Question 1

What is meant by mutations

Answer 1

Permanent change in DNA sequence can be altered in base of sequence of mRNA or by changes in amino acids sequence of a protein

Question 2

Types of mutations

Answer 2

Point mutation
(Missense mutation)
(Non sense mutation)

Frame shift mutation

Trinucleotide repeat expansion

Splice site mutation

Question 3

What is point mutation

Answer 3

Substitution of original base in gene by another

Question 4

What are the 2 forms of point mutation

Answer 4

Transition:
Purine is replaced by purine or pyrimidine with pyrimidine

Transversion:
Purine replaced by pyrimidine or pyrimidine with a purine

Question 5

Consequences of point mutation are:

Answer 5

Silent
Missense
Non sense

Question 6

What is silent mutation

Answer 6

Codon containing the changed base may code for same amino acid (usually change is in third base)

Question 7

What is Missense mutation

Answer 7

Codon changed may code for a diff amino acid

Question 8

What are results of missense mutation

Answer 8

Acceptable: AAA»»AAU
from lysine to asparagine
Which produces functional Hb

Partially acceptable: GAA»»GUA
Glutamic acid»»valine
Produces HbS which can bind to O2 but not in low O2 saturation

Unacceptable: CAU»»>UAU
Histidine»»tyrosine
Produces HbM which cant transport O2

Question 9

What is hereditary hemochromatosis

Answer 9

Associated with two well known Missense mutations in HFE gene
Disorder of iron metabolism which results in liver damage,diabetes,skin pigmentation and heart failure

Question 10

What is non sense mutation

Answer 10

Codon containing changed base may become termination codon and produce shortened protein

Question 11

What is frame shift mutation

Answer 11

Results from deletion or insertion of one or more nucleotides in DNA that generate altered m RNAs with diff effects on protein structure

Question 12

What is trinucleotide repeat expanision

Answer 12

Sequence of 3 bases that is repeated in tandem is amplified so too many copies of triplet occur

Question 13

How does Huntington’s occur

Answer 13

Insertion of extra glutamine residues in protein

Question 14

What is splice site mutation

Answer 14

Mutation at splice site can alter way introns are removed from pre mRNA and produce aberrant proteins

Question 15

What is polymorphism

Answer 15

Change in genotype that has no effect on phenotype or harmless effect
Can cause increase susceptibility to a disease

Question 16

Types of polymorphism

Answer 16

Single base change: “snips” variation involves just one base
Tandem repeats: VNTRS can give rise to polymorphism. VNTRS are short DNA sequences that give the individual their “fingerprint”