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character
a heritable feature that varies among individuals
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trait
each variant for a character (ex: purple or white flowers)
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hybridization
the mating/crossing of two true-breeding varieties (Crossing a plant with purple flowers with a plant with white flowers)
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allele
alternative versions of genes (in pea plants, purple flowers on a plant or white flowers)
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the law of segregation
two alleles for a heritable character segregate during gamete formation and end up in different gametes; aka an egg or sperm gets only one of the two alleles that are present in the somatic cells of the organism making the gamete
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testcross
breeding an organism with an unknown genotype with a recessive homozygote; will reveal the genotype of said organism
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monohybrid
when a progeny is all heterozygous for one character
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dihybrid
individuals heterozygous for two characters
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law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation; applies mostly to alleles controlled by genes on different chromosomes
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complete dominance
the phenotypes of heterozygotes and dominant homozygotes are undistiguishable
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incomplete dominance
when neither allele is comepletely dominant and F1 hybrids have a phenotype somewhere in the middle of the two parental varieties; ex: red/white snapdragons, roan coloring in cows; heterozygotes have an intermediate phenotype
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codominance
two alleles affect the phenotype in seperate ways; aka different phenotypes expreseed together; ex: blood type, and MN molecules in blood
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pleiotropy
when a single gene influences most genes have multiple phenotypic traits
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epistasis
a gene at one locus alters the phenotypic expression of a gene at a second locus
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quantitative characters
when an either-or classification is impossible because the characters vary in the population along a continuum (in gradiations)
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polygenic inheritance
the additive effect of alleles at multiple loci, or two or more genes on a single phenotypic character (opposite of pleiotropy)
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norm of reaction
describes the pattern of phenotypic expression of a single genotype across a range of environments; ex: has no effect on blood type, but a person's count of red/white blood cells can vary; broadest for polygenic characters
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multifactorial
many factors, both genetic and environmental, collectively influence people
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aminocentesis
tests can determine, by extracting amniotic fluid and examining the cells found, whether the developing fetus will have a disease or not
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chorionic villus sampling
CVS; a physician inserts a tube through the cervix into the uterus and removes a sample of tissue from the placenta; the cells removed have the same genotype as the fetus
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