Ch 9 Outline PDF

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Chapter 9 - Patterns of Inheritance

Heredity - the transmission of traits from one generation to the next

I.

A. Genetics and Heredity a. In an Abbey Garden Mendel used pea plants to study heredity Character: heritable feature that varies among individuals Trait: variant of a character Hybrids: offspring of two different purebred varieties P generation: parental plants F1 generation: hybrid offspring F2 generation: offspring of F1 plants -

b. Mendel’s Law of Segregation - the two alleles in a pair segregate into different gametes during meiosis Monohybrid Cross: mating of individuals differing at one genetic locus Alleles: alternative version of a gene Homozygous: an organism that has two identical alleles for a gene Heterozygous: an organism that has two different alleles for a gene Dominant allele: determines an organism’s appearance Recessive allele: has no effect on an organism’s appearance Phenotype: an organism’s physical appearance Genotype: an organism’s genetic makeup Gene Locus: a specific location of a gene along the chromosome c. Mendel’s Law of Independent Assortment - the inheritance of one character has

no effect on the inheritance of another Dihybrid Cross: the mating of parental varieties differing in two characters d. Using a Testcross to Determine and Unknown Genotype Testcross: a mating between an individual of dominant phenotype but unknown genotype and a homozygous recessive individual e. The Rules of Probability Rule of multiplication: the probability of a compound event is the product of the separate probabilities of the independent events f. Family Pedigrees Wild-type traits: seen most often in nature Pedigree: a family tree g. Human Disorders Controlled by a Single Gene Most human genetic disorders are recessive . Cystic Fibrosis: most common lethal genetic disease in the U.S B. Variations on Mendel’s Laws a. Incomplete Dominance in Plants and People Incomplete Dominance: a type of inheritance in which the phenotype of a heterozygote is intermediate between the phenotypes of homozygotes b. ABO Blood Groups

the two types of

.A person’s blood type may be A, B, AB, or O c. Pleiotropy and Sickle-Cell Disease Pleiotropy: the control of more than one phenotypic character by a single gene Sickle-Cell disease is one example of pleiotropy in humans d. Polygenic Inheritance: the additive effects of two or more genes on a single phenotypic character e. Epigenetics and the Role of Environment Many phenotypic characters result from a combination of heredity and environment Epigenetic inheritance: the transmission of traits by mechanisms not directly involving DNA sequence C. The Chromosomal Basis of Inheritance a. Chromosome theory of inheritance: genes are located at specific positions on chromosomes and the behavior of chromosomes during fertilization accounts for inheritance patterns a. Linked Genes: genes located near each other on the same chromosome b. Sex Determination in Humans An offspring’s sex depends on whether the sperm cell that fertilizes an egg bears an X or a Y chromosome c. Sex-Linked Genes: genes located on sex chromosomes

meiosis and...