Extensions and Modifications of Mendelian Genetics Flashcards
Dominance
Phenotype of the homozygote is the same as the phenotype of the heterozygote
Codominance
Phenotype of the heterozygote includes the phenotype of both homozygotes (e.g. mottled flowers)
Incomplete Dominance
Phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes
Penetrance
Percentage of individuals with a certain genotype that express the phenotype
Expressivity
The degree or severity to which the phenotype is expressed
Lethal alleles
Cause death at an early stage of development so some genotypes do not appear among the progeny
Multiple alleles
More than two alleles present within a group of individuals (e.g. ABO blood group)
Gene interaction
Effects of genes at one locus depend on the presence of genes at other loci producing novel phenotypes
Epistasis
One gene masks the effect of another gene
Recessive epistasis
ABO blood groups - recessive Bombay phenotype controls expression of ABO
Dominant epistasis
e.g. Squash pigmentation - Dominant allele inhibits the conversion of Enzyme A into Enzyme B
Duplicate recessive epistasis
Two enzymes must be recessive in order to display the phenotype
Genetic complementation
Multiple genes complement each other to produce a given phenotype (e.g. coat color in dogs)
Sex-influenced characteristics
Same genotype expressed differently in males vs. females
Sex-limited characteristics
Same genotype only expressed in one sex vs. another
Mitochondrial characteristics
Vary wildly based on population frequency of randomly assorted mitochondria
Genomic imprinting
Differential expression of genetic material depending on whether it is inherited from the male or female parent
Epigenetics
Phenomena due to alterations to DNA that do not include changes to DNA sequence which often affect the way DNA is expressed, e.g. methylation
Genetic maternal effect
The genotype of the maternal parent determines the phenotype of the offspring
Genetic anticipation
A genetic trait becomes more strongly expressed or expressed at an earlier stage as it is passed from generation to generation (e.g. Fragile X Syndrome)
Temperature-sensitive allele
An allele whose product is functional only at a certain temperature
