L23 Mutations Flashcards

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1
Q

What is meant by mutations

A

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

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2
Q

Types of mutations

A

Point mutation
(Missense mutation)
(Non sense mutation)

Frame shift mutation

Trinucleotide repeat expansion

Splice site mutation

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3
Q

What is point mutation

A

Substitution of original base in gene by another

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4
Q

What are the 2 forms of point mutation

A

Transition:
Purine is replaced by purine or pyrimidine with pyrimidine

Transversion:
Purine replaced by pyrimidine or pyrimidine with a purine

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5
Q

Consequences of point mutation are:

A

Silent
Missense
Non sense

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6
Q

What is silent mutation

A

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

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7
Q

What is Missense mutation

A

Codon changed may code for a diff amino acid

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8
Q

What are results of missense mutation

A

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

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9
Q

What is hereditary hemochromatosis

A

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

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10
Q

What is non sense mutation

A

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

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11
Q

What is frame shift mutation

A

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

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12
Q

What is trinucleotide repeat expanision

A

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

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13
Q

How does Huntington’s occur

A

Insertion of extra glutamine residues in protein

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14
Q

What is splice site mutation

A

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

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15
Q

What is polymorphism

A

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

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16
Q

Types of polymorphism

A

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”