Chapter 7 Flashcards
Mutation
A change in the genetic material
Most common type of mutaiton
Point mutation
Point Mutation
Mutation mapped to a single location or point
Substitution, insertion, or deletion of a single base pair or of a small number of adjacent base pairs
Chromosomal mutation
Rearrangement (inversion, translocation), duplication, or deletion of a segment of (or entire) chromosome
Ex: aneuploidy
Aneuploidy
Abnormal number of chromosomes
Ex: trisomy
If a point mutation occurs outside of a gene….
Will not change phenotype
If a point mutation occurs inside a gene…
May or may not change phenotype
If a gene mutation occurs in promoter, affects…
Transcription
If a gene mutation occurs in 5’ or 3’ UTR, affects….
Translation
If a gene mutation occurs in an intron, affects…
Splicing
If a gene mutation occurs in a protein-coding region, affects…
Function or production of protein
May or may not result in altered phenotype
2 categories of point mutations
Base-pair substitutions (transition and transversion)
Base pair insertions or deletions (indel)
Transition
Replacement of base by other base of same chemical category
Purine to purine or pyrimidine to pyrimidine
Transversion
Replacement of a base by another of a different category
Purine to pyrimidine and vice versa
Silent mutation
No changes to protein sequence
Indel mutation
Base-pair insertion or deletion
Sometimes may involve simultaneous addition or deletion of multiple base pairs
Frameshift mutation
Can be caused by an addition or deletion of any number of bases not divisible by 3
Changes whole reading frame
Often results in nonfunctional protein
Can be generated by DNA looping-out
Types of point mutations in protein-coding region
Change amino acid sequence
Missense
Nonsense
Neutral
Missense
Mutation in which an amino acid is changed to a different one
Can be caused by transition or transversion
May or may not result in phenotype change
Nonsense
Mutation in which amino acid is replaced with one of the stop codons
Leads to premature stop codon and shortened polypeptide
Can be caused by transition or transversion
If it appears early in sequence, will most likely result in nonfunctional protein
Neutral mutation
An amino acid is changed to a different but chemically similar amino acid
Type of missense mutation
Most likely will not affect protein function
Silent mutation
New codon encodes same amino acid
No changes to amino acid sequence or protein function
Start codon mutation
Important for binding of initiation tRNA to mRNA and formation of initiation complex
Product most likely out of frame or shortened
Spontaneous mutations
Naturally occurring mutations
10^-4 to 10^-6 per gene per generation
