Types of mutations and pedigrees Flashcards
pedigree
a record of descent using symbols to track inheritance and mutations
pedigree assumptions
if the trait is RARE and autosomal recessive, then individuals who marry/mate into the pedigree are not carriers - they are homozygous for the “normal” allele
- unless there is evidence to contrast
recessive mutations
often involve a loss of gene function
- no affect on phenotype if you have one normal copy
Null/ Amorphic alleles
implies there was a mutation in the promotor sequence, results in…
a) a non-functional protein produced OR
b) no protein produced
Hypomorphic alleles
a) a poorly functioning protein is produced
b) reduced amounts of a normally functioning protein are produced
multiplication rule
What is the chance of getting a AND b (multiply probabilities together)
addition rule
What is the chance of getting a OR b (add probabilities together)
gain of function mutation
the mutant allele produces a protein that has increased (detrimental) function
Wild-type phenotype (a^+)
wild-type allele produces a functional polypeptide
when a recessive amorphic loss-of-function allele does not produce a functional peptide
Severe mutant phenotype (a)
- slight change in the conformation of the protein effects its folding
Mild mutant phenotype (a^h)
recessive hypomorphic loss-of-function allele produces a partially functioning polypeptide
when a dominant-negative allele produces a polypeptide that interferes with the wild-type polypeptide
sever mutant phenotype (a^D)
- changed an amino acid in the protein sequence
- new or better function
mutation phenotypes
a+ and a = wild-type phenotype
a+ and ah = wildtype phenotype
a+ and aD = mutant phenotype
aD > a+ > a = ah
- shows that dominant negative overrides wild type
what do most genes encode?
polypeptides
recessive mutations in homozygous condition
abolish or diminish polypeptide activity
