Lecture 10-11 Flashcards
What is the max number of diff. alleles for a single gene that one person can have?
2, one from each parent
What is the maximum number of alleles for a single gene that can be observed in a population?
Many
eg. socks (only two per pair, but the combinations are endless)
**Define haplosufficient.
when one wild type allele is sufficient to produce the wild-type phenotype
aka. similar result as complete dominance
**What is the difference between dominance/recessive and sufficiency?
Genes can be haplo(in)sufficient, but only mutant alleles can be dominant or recessive
**Define haploinsufficient.
When the wild-type allele is recessive
Define wild-type.
describes the trait/allele that is most common in a natural population
Define null/amorphic.
“zero” or “w/o form”
A loss of function mutation which produces no functional gene (abnormal products)
-often recessive and lethal in homozygous genotype
Define dominant negative.
a loss of function mutation and result of abnormal polypeptide interaction–> dominant
Define hypomorphic.
aka a leaky mutation
a loss of function mutation resulting in partial loss of gene function
-often recessive and homozygous is lethal
Define hypermorphic.
a gain of function mutation increased gene activity, “overdrive”
lethal in homozygotes
Define neomorphic.
a gain of function mutation where the gene gains activities not found in the w+
Define incomplete/partial dominance.
When a phenotype in a heterozygous organism is an intermediate between the homo. phenos., but more similar to one pheno, than the other
Define codominance.
The equal and detectable expression of both alleles in a heterozygous organism.
**Define allelic series.
A group of alleles of a genes that display a hierarchy of dominance relationship among them.
Define temperature-sensitive allele.
A mutation evident only at or above a certain temp, due to an abnormality of the protein product that affects stability.
How does a lethal allele affect phenotypic ratios?
One genotype is not present (failure to produce the affected category of progeny)
-Mendelian: 1:2:1
-Lethal allele: 2:1
–> the mutant allele is both dom and rec
Why does Huntington Disease (HD) have delayed age of onset?
-symptoms are due to neuron death which usually takes place over several decades
What is meant by “delayed age of onset”?
-“side steps natural selection” aka doesn’t appear until after affected organisms have been able to pass down the gene
Define penetrance.
the expression of phenotype corresponding to a particular genotype
iow. if dominant trait is present, org. presents dominant pheno
eg. polydactyly
Define expressivity.
the phenomenon where the same genotype produces varying degrees of phenos
eg. Waardenburg syndrome (HOH, heterochromia, white lock of hair, premature hair graying)
Define gene-environment interactions.
describes the influences of environmental factors on genes and the phenos of organisms
eg. plant height based on soil/water/sunlight conditions
Define pleiotropy.
a single gene mutation altering multiple seemingly unconnected features of an org., iow secondary effects due to an mutant allele
-often seen in developmental diseases
eg. sickle cell disease
Define epistasis.
gene interactions that modify or prevent the expression or alleles of another gene
Define genetic complementaiton.
An epistatic interaction where genes must act together to produce a phenotype
–>indicates that multiple genes are used to code for one phenotype
eg. sweet pea flower color
9:7 ratio
Define complementation group.
a group of mutations that effect the same gene
