• Mendelian genetics o Character: inheritable feature, i.e., fur color o Trait: variant for a character, i.e., brown o True-bred: all off-spring of same variety o Hybridization: crossing of two different true-breds o P generation: parents o F1 generation: first filial generation
• Leading to the law of segregation o Alternative versions of genes (alleles) account for variations in inherited characteristics. o For each character, an organism inherits 2 alleles, one from each parent. o If the two alleles differ, then one, the dominant allele, is fully expressed in the organism’s appearance, the other, the recessive allele, has no noticeable affect on the organism’s appearance. o The alleles for each character segregate (separate) during gamete production (meiosis).
• Genetic Vocabulary o Punnet square: predicts the results of a genetic cross between individuals of a known genotype. o Homozygous: pair of identical alleles for a character (ex/ pp) o Heterozygous: two different alleles for a gene (ex/ Pp) o Phenotype: an organism’s traits. o Genotype: an organism’s genetic makeup. o Testcross: a cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait so the unknown genotype can be determined from the offspring.
• Law of independent assortment o Law of segregation involves 1 character. What about 2 or more characters…? o Monohybrid cross (hybridization using a single trait with two alleles) vs. Dihybrid cross (hybridization using two traits with two alleles each) o The two pairs of alleles segregate independently of each other.
• Non-single gene genetics o Incomplete dominance: appearance between phenotypes between the 2 parents. (Ex/not enough pigmentation in snapdragons) o Codominance: two alleles affect phenotype in separate ways. o Multiple alleles: more than 2 possible alleles for a gene. (Ex/ human blood types) o Pleiotrophy: genes with multiple phenotypic effects. (Ex/ sickle cell) o Epistasis: a gene at one locus (location) affects the phenotypic expression of a gene at a second locus. (Ex/ Mice coat color) o Polygenic Inheritance: an additive affect of two or genes on one phenotype. (Ex/ human height)
• Human Disorders: o The family pedigree o Recessive disorders
• Cystic fibrosis
• Tay-sachs
• Sickle-cell o Testing
• Amniocentesis
• Chronic virus sampling (CVS) o Dominant disorders
• Huntington’s Disease
• Dwarfism
• Anchondroplasia
• S.E.D.
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