🧬 Mutations, SNPs, Epigenetics & Gene Expression

What is a mutation?

A change in the DNA sequence. Can be silent, missense, nonsense, or frameshift.

What is a SNP?

Single Nucleotide Polymorphism. A one-base change present in >1% of the population. Used as genetic markers.

What is the difference between a mutation and a SNP?

Mutation = any change (often rare or new). SNP = common polymorphism (>1% frequency).

What is epigenetics?

Heritable changes in gene expression that do NOT involve changes to the DNA sequence. Includes DNA methylation, histone modification, and non-coding RNAs.

What is DNA methylation and what does it usually do?

Addition of methyl groups to CpG sites. Usually represses gene expression.

What are histone modifications?

Chemical changes to histone tails (acetylation, methylation, phosphorylation) that alter chromatin structure and gene accessibility.

What is the difference between euchromatin and heterochromatin?

Euchromatin = open, active transcription. Heterochromatin = condensed, repressed.

What is gene expression regulation?

Control of when, where, and how much a gene is transcribed. Includes promoters, enhancers, silencers, transcription factors, and epigenetic marks.

What is a transcription factor?

A protein that binds DNA to activate or repress transcription.

What is alternative splicing?

One gene can produce multiple mRNA variants by splicing exons differently. Increases protein diversity.