Gene mutations: substitutions, frameshifts, oncogenes, p53

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Gene Mutation:

- Inherited change in DNA nucleotide seq

-Base-pair substitution result in change in corresponding codon

- Base-pair insertion/ deletion result in frameshift mutation

Explain how a mutation in a ____ gene could affect structure of its product?

Bp insertion/deletion result in frameshift

Change in mRNA codon seq -> Change in a.a. seq

Affect folding of protein - change in 3D/tertiary structure of protein -> Change in binding site

Protein coded for may (i) be non-functional (ii) no longer synthesised.

Why loss of function mutation in a tumour-supressor gene results in a recessive allele?

Mutation have to occur in both gene copies for cancer to develop

In heterozygotes, the effect of mutation is masked by the normal dominant allele -> result in sufficient qty of protein synthesised

Why gain of function mutation in a proto-oncogene results in a dominant allele?

Mutation have to occur in only one gene copy for cancer to develop

In heterozygotes, the effect of mutation is shown by the single mutated dominant allele -> result in excessive qty of protein synthesised

Why does p53 protein only bind to certain parts of DNA molecule?

Diff seq of bases on DNA have diff shapes

Binding site of p53 has specific shape

Which is complementary to that of the portion of DNA molecule

Major and minor grooves: Proteins can bind within these grooves and interact with a particular seq of bases

What is proto-oncogene?

Gene that codes for proteins that stimulate normal cell division

What is oncogene?

Mutant form of proto-oncogene that controls normal cell division

Leads to increase in either: Amt of proto-oncogene's protein or intrinsic activity of protein molecules

Oncogene pdt acts in a dominant fashion -> Excessive cell division

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