Gene Interaction Flashcards
A phenotype can be influenced by __ if not __ of the genes that an organism posses
Many if not most if the genes an organism posseses
Two ways that genes can interact
- Interactions between alleles of the same gene
- Interactions berween two or more different genes
Genes are long stretches of DNA that comprise many opportunities for ___
Mutation
With complete dominance, this intermediate level will be sufficient, resulting in Wild Type
Why?
Happlosufficient
With Complete Dominance there is enough gene activity in the heterozygote
___ occurs when one Wild Type copy of a gene is insufficient
Why?
Happloinsufficiency
There is not enough gene activity in the heterozygote
What is a dominant negative?
It does not function properly and it impairs the wild type allele
What do heterzygotes exhibit in incomplete dominance?
They exhibit an intermediate phenotype
What is codominance?
Heterzygote exhibits the phenotypes associated with both alleles of a gene
What is a lethal allele?
Capable of causing death of an organism
What are essential genes?
Genes that without which an organism dies
What are conditional essential genes?
Genes that are essential in some individuals but not others.
Peliotropic:
An allele that affects several properties of an organism
Temperature sensitive mutations:
These are heat sensitive alleles
Permissive temperature:
ts mutants exhibit wild type phenotype
Restrictive temperature:
ts mutants exhibit mutant phenotype
Penetrance:
The percentage of individuals with a given allele who exhibit the phenotype associated with that allele.
Incomplete penetrance:
When penetrance is less than 100%
Expressivity:
The intensity of the phenotype resulting from a given mutation.
Variable expressivity:
When the severity of the mutant phenotype varies across individuals
Factors that influence expressivity(5)
Environment
Alleles at the same gene
Genetic variation in other interacting genes
Stochastic factors
Mutant phenotype is subtle, making it difficult to measure
Auxotrophic mutation:
Only grows if fed a specific metabolite
Beadle and Tatum proposed that genetic results reflected the existence of a ___ ___
Biochemical pathway
Genes encode proteins which in turn __ ___ __
Perform some function
How many pathways do genes function in?
3
What are the 3 pathways that genes function in?
Biosynthetic
Signal Transduction
Developmental
Biosynthetic pathway:
Generation and interconversion of metabolic products
Signal transduction pathway:
A cascade that ultimately influences the transcription of specific genes in response to a particular cue
Developmental pathway:
Pathways that underlie the steps in a zygote becoming an adult organism
Mutations in different genes will typically result in a ___ ___ ___ or ___
wild type phentotype or complementation
If mutations occur in the same gene it is ___ that they will complement each other.
Why?
unlikely
Because both copies are broken
What happens when mutations are in different genes that reside in the same pathway?
Mutations in the same pathway results in a 9:7 ratio
Epistasis:
When the phenotypes of double mutants depart from expectations based on single mutants.
Recessive epistasis:
When the recessive allele of one gene masks the effects of either allele at the second gene
Dominant epistasis:
When the dominant allele of one gene masks the effects of the either allele at the second gene
Suppressors:
A mutant allele of one gene that reverses the effect of a mutation in another gene, resulting in a wild-type or near wild type phenotype
Modifiers:
Mutations at a second locus that change the degree of expression of a mutation at a first locus.
Synthetic lethality:
Crossing two viable single mutants produces a lethal combination of two mutations
