Ch. 5 Extensions on Mendel Flashcards
Lethal alleles
causes death at an early stage of development (often before birth) so that some genotype do not appear among the progeny
incomplete dominance
heterozygote is intermediate (phenotype is between the homozygotes)
codominance
heterozygote exhibits both phenotypes
Penetrance
the percentage of individuals with a particular genotype that express the expected phenotype
True or false: in incomplete dominance the phenotypic ratio with match the genotypic ratio
true
(both are 1:2:1)
Genes at multiple loci determine
a single phenotype (products of different loci combine to produce a phenotype)
Epistasis
One gene hides/masks the effect of another gene at a different locus
Cystic fibrosis is an example of
a compound heterozygote
What is a compound heterozygote
an individual who carries 2 different alleles at a locus that result in a recessive phenotype (cystic fibrosis)
recessive epistasis
the presence of 2 recessive alleles inhibits the expression of an allele at a different locus
dominant epistasis
the presence of a single copy of an allele can inhibit the expression of an allele at a different locus
epistatic gene
the gene that does the masking
hypostatic gene
the gene whose effect is masked
incomplete penetrance
describes individuals with the same genotype that do not exhibit the same phenotype (genotype does not produce expected phenotype)
How do you calculate penetrance
number of individuals with phenotype/ total number of individuals
Sex influence trait
a trait determined by an autosomal gene that is more prominently expressed in one sex
sex limited trait
a trait determined by an autosomal gene that is expressed in only one sex
pleiotrophy
a gene that affects more than one phenotype
polygenic trait
a trait that is determined by multiple genes
Imprinting
a trait that is at least partially determined by the sex of the parent of origin
In lethal alleles when you cross 2 individuals with a lethal allele what is the pheno ratio you get
2:1 (instead of our normal 3:1); 2 show what the parents had shown, the 1 shows the recessive (there is another 1/4 but they are dead so they are not included)
true or false: phenotypes are not preductable from single-locus effect alone
true: interaction among genes at 2, 3, 4 or more loci is common
expressivity
the degree to which a character is expressed
sex-linked
genes on X or Y chromosomes
continuous characteristics
polygenic and influenced by the environment= multifactoral
