Genetic variation

Question 1

Mutation definition

Answer 1

Stable, heritable changes in DNA that happen in one cell and passed down.

Question 2

Types of mutations

Answer 2

• Somatic (can give mosaic)
• Germline
• De novo (not in parents)
  /
• Spontaneous (replication errors, endogenous chemical damage, errors in segregation)
• Induced (mutagens)

Question 3

Types of mutations depending on dimensions

Answer 3

• Chromosome-number variations
• Structural variation
• Point mutations

Question 4

Chromosome-number variations

Answer 4

• Aneuploidy (monosomy usually lethal if not sexual, trisomy like Down more tolerated in small chromosomes)
• Polyploidy (more than 2 haploid sets)

Question 5

Structural variations

Answer 5

Copy-number variations, effect depending on dimension and type:
- Insertions
- Deletions
Balanced structural variants, phenotypically invariant but gametes might be affected
- Translocations (can give fusion gene, Phildadelphia, Robertsonian in 21+14)
- Inversions

Question 6

Type of point mutations

Answer 6

• Transitions (purine to purine, pyrimidine to pyrimidine)
• Transversions (purine to pyrimidine or vice versa)
  Or:
• Base-pair substitutions (SNPs if MAF>1% or SNVs)
• Base-pair indel
  Can give regulatory mutations if outside of exons

Question 7

Point mutations based on aminoacid effect

Answer 7

• Silent/synonimous (same AA)
• Missense (different AA)
• Nonsense (STOP codon)
• Frameshift (change in open reading frame)