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complete dominance
heterozygous phenotype for one of the homozygotes TERM 2
incomplete dominance
DEFINITION 2 heterozygous phenotype is intermediate between the two homozygous phenotypes flower color in snap dragons cream dilution gene of horses TERM 3
codominance
DEFINITION 3 heterozygous phenotype includes both of the homozygous phenotypes roan coat color incattle tabby color in cats TERM 4
penetrance
DEFINITION 4 percentage of a population that shows the expected phenotype TERM 5
expressivity
DEFINITION 5 degree or intensity with which a particular genotype is expressed in a phenotype
reasons for differences in penetrance and
expressivity
modifier genes environmental factors allelic variation complex genetic and environmental interaction stochastic variation in gene expression networks TERM 7
pleiotropy
DEFINITION 7 one gene affects multiple characteristics, that may or may not be obviously related to each other TERM 8
epistasis
DEFINITION 8 an allele of one gene modifies or prevents the expression of alleles at another gene TERM 9
epistatic
DEFINITION 9 the overriding gene TERM 10
hypostatic
DEFINITION 10 the masked allele
complementation
F1 proven have a wildtype phenotype because the mutations affect 2 different genes TERM 17
no complementation
DEFINITION 17 F1 progeny have a mutant phenotype because the same gene is affected in both mutants TERM 18
sex-limited traits
DEFINITION 18 genes that control the trait are autosomal but their expression occurs only in one sex or the other trait appears in only one sex Examples: Mammary glands --> milk chickens TERM 19
sex influenced traits
DEFINITION 19 controlled by autosomal genes but are influenced by hormone levels male pattern baldness bearded goats TERM 20
genetic maternal
effect
DEFINITION 20 phenotype of offspring is NOT determined by its own genotype but rather the genotype of the mother cytoplasmic transmission of products of nuclear genes offspring alleles from both parents usually observed because of maternal gene products needed during early embryonic development snail coiling
genomic imprinting
differential expression of a small number of autosomal genes is based from male or female parent TERM 22
paternal imprinting
DEFINITION 22 allele inherited from the father is transcriptionally silenced offspring that inherit mutant allele from mother are affected offspring that inherit mutant allele rom father are NOT affected TERM 23
maternal imprinting
DEFINITION 23 allele inherited from the father is transcriptionally silenced offspring that inherit mutant allele from mother are NOT affected offspring that inherit mutant allele rom father ARE affected Igf2 gene mice TERM 24
anticipation
DEFINITION 24 a trait becomes more severe or is expressed at an earlier age at succeeding generations in humans, often seen in disorders of the nervous system usually because of unstable size of repeat sequences in or near genes also seen in syndromes with progressive telomere shortening TERM 25
phenocopy
DEFINITION 25 environmental factors alone produce a phenotype that is identical to a phenotype caused by genotype
