Chapter 5 Flashcards
Complete Dominance
an allele or phenotype that is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in the heterozygous phenotype
Incomplete Dominance
The phenotype of a heterozygote that is intermediate between the phenotypes of the two homozygotes
Codominance
when the phenotype of the heterozygote expresses the phenotypes of both homozygotes
Incomplete Penetrance
a phenomenon where the genotype does not produce the expected phenotype
ex: human polydactyly: having extra fingers or toes
Penetrance
the percentage of individual organisms having a particular genotype that express the expected phenotype
Expressivity
the degree to which a character is expressed
ex: some polydactylous people have extra fingers/toes that are fully functional, whereas others posses only a small tag of extra skin
Lethal Allele
causes death of an early stage of development (often before birth) which leads to some genotypes that may not appear among the progeny
Multiple Alleles
more than 2 alleles at a locus in a group of individuals - each member of the group has only 2 of the possible alleles
Gene Interaction
interaction between genes at different loci that affect the same characteristic
with gene interaction the product of genes at different loci combine to produce new phenotypes that are not predictable from the single-locus effects alone
Epistasis
When the effect of gene interaction masks the effect of another gene at a different loci
Sex-Influenced Characteristics
determined by autosomal genes but are expressed differently in males and females
ex: body hair
Sex-Limited Characteristics
an extreme form of sex-influenced characteristics; determined by autosomal genes that are only expressed in one sex
Genomic Imprinting
the different expression of genes which depends on whether they were inherited from the mother or father
ex: Igf2 - encodes a protein called insulin-like growth factor II - sometimes it is only expressed when transmitted by the father and vice versa
Epigenetics
phenomena due to changes in DNA that do NOT inclues changes in base sequence; often affect the way in which the DNA sequences are expressed.
Such alterations are often hereditable from one cell to another
Temperature-Sensitive Allele
an allele whose product is functional only at certain temperatures
