chapter 4 part 1 Flashcards
(36 cards)
the ways genes interact to influence ____________
a phenotype
several important types of gene interactions
- more than 2 alleles for given locus
- dominance may not be complete
- 2+ genes may affect single trait
- expression of trait depends on interaction of 1+ gene with non-genie factors
Mendel chose to examine traits with _______ alternative forms
two
- in each case, one form was completely dominant over the other
the terms dominant and recessive have a _____________ basis
biological
what is the dominance of one allele over another determined by?
protein product of that allele
the overall phenotype is the consequence of what?
activities of the protein products of the alleles of the gene
mutant allele recessive to wild type
- wild type R+ produces active enzyme (50 units)
- mutant allele produces little/no active enzyme (0 units)
- 40+ units = wild type phenotype
- R+ + R+ = 100
- R+ + r = 50
- r + r = 0
mutant allele dominant to wild type
- allele T1 produced active enzyme (10 units)
- mutant allele T2 produces less active enzyme (5 units)
- 18+ units produces wild type
- only T1T1 (20 units) - wild type
- heterozygous and homozygous for mutant allele both mutant in phenotype
haplosufficient
one copy of wild type allele enough for normal function
haploinsufficient
one copy of wild type allele isn’t enough for normal function
when is a wild-type phenotype always produced?
when an organisms has 2 copies of wild type allele
2 types of mutant alleles:
- gain-of-function
- loss-of-function
gain-of-function
when gene product acquires new function or shows and increased level of wild type activity
loss-of-function
when there is a significant decrease or complete loss of functional gene product
2 types of loss-of-function mutations
- null/amorphic mutation
- leaky/hypomorphic mutation
null/amorphic mutation
produce no functional protein product
- often lethal when homozygous
leaky/hypomorphic mutation
partial loss of function
- severity of phenotype depends on level of activity of leaky mutation
multimeric proteins
composed of 2+ polypeptides that join together to form a functional protein
what are multimeric proteins subject to
dominant negative mutations
why are dominant negative mutations dominant
due to loss of function of multimeric protein complex due to amino acid change in one subunit
how are dominant negative mutations negative?
due to “spoiler effect” on protein as whole
are gain-of-functions usually dominant or recessive?
dominant
types of gain-of-function mutations
- hypermorphic
- neomorphic
hypermorphic mutations
produce more gene activity than wild type
