Lectures 3-5 Flashcards
How many alleles exist in a diploid cell for one particular gene?
2
What is haplosufficiency?
Wild type is dominant over loss of function allele, less protein, but is often sufficient enough to achieve wild type phenotype
What is a gain of function mutation?
Mutant allele produces a protein that has increased detrimental function
Haploinsufficient?
Half as much protein is synthesized, and this is now sufficient for normal phenotype
What is a recessive lethal allele?
Essential genes, when mutated, lead to lethal phenotype, homozygous is lethal
What is a dominant lethal allele?
Can be expressed in both homozygous and heterozygous
How do recessive mutations impact the polypeptide?
Diminish polypeptide acitivity
What is penetrance?
Proportion of individual organisms having a particular genotype that express the expected phenotype - variation in the population
What is expressivity?
The degree to which a phenotype is expressed - variation in the individual
What causes penetrance and expressivity?
Due to effects of environmental factors and other genes
What are some environmental factors that affect phenotypic expression?
Age, sex, temperature, chemicals
What is a phenocopy?
Change in phenotype arising from environmental factors that mimic the effects of a mutation in a gene
What is the law of independent assortment?
Inheritance of one trait will not affect the inheritance pattern of another trait
What is genetic interaction?
Different combinations of alleles from two+ genes can result in different phenotypes
What is complementation?
Occurs when two strains with different homozygous recessive mutations that produce the same phenotype produce offspring with wild type phenotype when crossed. Only occurs if mutations are in different genes
What is a heterogeneous trait?
Mutation in any one of a number of genes can give rise to the same phenotype?
What is epistasis?
Masking of the expression of one gene by another
Recessive epistasis?
Recessives one one gene pair mask expression from another gene
Dominant epistasis?
One dominant allele at one gene masks the expression from the other gene
F2 ratios?
3:1 - complete dominance
1:2:1 - incomp. Dominance or co-dom
2:1 - recessive lethal
9:3:3:1 - complete dominance
9:3:4 - recessive epistasis
9:7 - complementation
12:3:1 - dominant epistasis
What is pleiotropy?
Single gene can be responsible for number of distinct and seemingly unrelated phenotypic effects
What is inbreeding depression?
Inbred lines of species are less vigorous than hybrid
Hybrid vigour (heterosis)
When two different inbred lines are crossed, hybrids are vigorous
What is the hardy-Weinberg equilibrium?
p^2 + 2pq + q^2 = 1
What is X-inactivation?
Random inactivation of one x from females, if a cell contains more than one X chromosome, all but one are inactive, e.g. Barr bodies XXX has two Barr bodies
