Lecture 1: Mutation

What is the difference between a Germ-line and a somatic mutation?

Germ-line mutations occur in gametes (sperm/egg), affect the whole body, and are passed to offspring. Somatic mutations occur in body cells, affect only a localized area, and cannot be passed down.

What is a transition vs. a Transition point mutation?

Transition swaps purine for curing (A ←→G) or pyrimidine for pyrimidine (C←→T). Transversion swaps a purine for a pyridine or vice versa.

What happens in a silent Mutation?

A base changes, but the new codon encodes the exact same amino acid, leaving the protein unchanged.

what happens in a nonsense mutation?

A base change converts an amino acid Condon into a premature STOP codon, chopping the protein short.

What is the difference between a hypomorph and a Null (amorphous) mutation?

A hypomorph causes a partial loss of function. A null/Amorph causes a complete loss of function.

What is a neomorph mutation?

A gain of function mutation where the gene product gains an entirely new function or new expression pattern.

What is Depurination?

A spontaneous loss of an adenine (A) or guanine (G) base from DNA creating an empty apurinic site.

What causes genetic anticipation in repeat expansion disorders like Huntingtons disease?

DNA polymerase slippage forms hairpins during replication, increasing the number of trinucleotide repeats in future generations leading to earlier onset and more severe disease.

which DNA repair pathway uses a sister chromatid as a template to repair double-strand break without losing data?

Homologous recombination repair ( occurs during S and G2 phases).

what is non-homologous end joining (NHEJ) and what is its trade-off?

it glues double-strand break together without a template during any cell cycle phase, but it chews back DNA ens usually leaves a small deletion.