Genetics and Heredity Chapter 8

Heredity—The passing of genes from parents to offspring. Genetics—The branch of Biology that focuses on heredity. Monohybrid cross– a cross involving one pair of contrasting traits. Dihybrid cross—a cross involving two pairs of contrasting traits.

True breeding—all of the offspring displays only one form of the character. P Generation (Parents)—The first to be crossed in a breeding experiment. F₁ Generation—Offspring of the P Generation. F₂ Generation—Offspring of the F₁ Generation.

Alleles—different versions of a gene. Ex. Flower color can be Purple or White (in Mendel’s Pea Plants). Dominant—the trait that is shown (masks) (B) Recessive—the trait that is not shown (masked). (b)

Homozygous—two alleles that are the same. Heterozygous—two alleles that are different. RR=homozygous rr=homozygous Rr=Heterozygous

Genotype—The set of alleles that a person has for a trait.(letters) Phenotype—The physical appearance of a trait. (eye color) Blue eyes (phenotype) bb (genotype)

Law of segregation—the two alleles for a trait separate when gametes are formed. Law of independent assortment—alleles of different genes separate independently of one another during gamete formation. Punnett Square—diagram that predicts the outcome of a genetic cross.

Test cross-- an individual whose phenotype is dominant, but whose genotype is not known, is crossed with an individual who is homozygous recessive.

Probability— chance that something will happen. Pedigree—a family history that shows how a trait is inherited over several generations.

Sex-linked genes— allele is located only on the X or the Y. Ex. Hemophilia Polygenic Inheritance– When several genes influence a character. (Ex. Eye color, hair color, height, weight) Incomplete dominance– When neither allele is completely dominant over the other. (Ex. Snapdragons—Red and white yield all pink flowers)

Codominance– both traits are displayed and one is not dominant over the other.

Multiple alleles– Genes with three or more alleles. (Ex. Blood types…ABO) Characters influenced by environmental factors--- Ex. Hydrangea flower is blue when in acidic conditions and pink when in basic conditions Ex. Arctic fox has a white coat in the winter and brown in the summer