Chapter 5 Flashcards
what does the phrase “gene interactions” refer to?
the ways genes collaborate or interact to influence a phenotype
what are 4 important types of gene interactions?
- There may be more than two alleles for a given locus within a population
- Dominance of one allele over another may not be complete
- Two or more genes may affect a single trait
- The expression of a trait may depend on the interaction of more than one gene and/or the interaction of genes with nongenic factors
what does the phenotype depend on?
the action of proteins that are encoded by a specific protein
what does haplosufficient mean?
one copy of an allele is enough for wild-type phenotype
-the dominant allele is this
what does haploinsufficient mean?
one copy of an allele is not enough for wild-type phenotype
-the recessive allele is this
what is a dominant negative mutation?
these mutations are dominant due to loss of
function of the multimeric protein due to an amino acid change in one subunit
-These are negative mutations due to their “spoiler” effect on the protein as a whole
what is particularly subject to dominant negative mutations?
Multimeric proteins, composed of two or more polypeptides that join together to form a functional protein
what is incomplete dominance?
also called partial dominance and is when
heterozygous individuals display intermediate
phenotypes between either homozygous type
what is codominance?
leads to heterozygotes with a different phenotype than that of either homozygote
Antigens relative to blood type?
-The A blood type involves the presence of one antigen on the blood cell surfaces
-type B the presence of a different antigen
-Type AB people have both antigens
-type O people have neither
what is a characteristic of lethal alleles?
Because they are recessive, lethal
alleles can “hide” in heterozygotes
and persist in a population
when is a trait penetrant?
when the phenotype is consistent with the genotype
when is a trait nonpenetrant?
when the genotype fails to consistently produce the expected phenotype
what is incomplete penetrance?
when traits are occasionally nonpenetrent
what is variable expressivity?
the same genotype produces a range of phenotypes that vary in degree
what are gene-environment interactions?
when the environment influences the phenotype that perhaps explains incomplete penetrance and variable expressivity in some
instances.
what is the “one gene-one enzyme” hypothesis?
where a single gene encodes a single enzyme
what is a prototroph?
strain that can synthesize all compounds required for growth
what is an auxotroph?
strain that is unable to synthesize all compounds required for growth
what is genetic dissection?
Determining the order of biochemical pathways using single-gene mutants and identifying the point at which the pathways is blocked
all mutants can grow on what part of the pathway?
the end-product
what is epistasis?
Gene interaction where alleles at one gene influence the function of alleles at another gene.
what is complementation?
complementary gene interaction occurs when genes must act in tandem to produce a phenotype
-wild-type action from both genes is required to produce the wild-type phenotype
-mutation of one or both genes produce a mutant phenotype
how do you determine what mutants are part of the same complementation group?
mutants that do not complement each other are part of the same complementation group, and mutations are on the same gene
What does the number of complementation groups tell you?
the number of genes involved in a trait
