Chapter 14 Mendel and the Gene Idea Mendelian

Chapter 14 Mendel and the Gene Idea

Mendelian Genetics u Mendel was able to describe a model of inheritance

Law of Segregation This principle helps to describe the inheritance of a single trait. u For each inherited trait there are 2 genes, they may be the same homozygous. Or different heterozygous. u Each sex cell carries one of the alleles to the offspring, therefore they are SEGREGATED at meiosis.

Testcrosses u u u A testcross is used to determine the genotype of a particular dominant phenotype. Perform a cross between the unknown genotype and a homozygous recessive. The appearance of a recessive offspring indicates the unknown was heterozygous.

Law of Independent Assortment Describes the inheritance combinations possible by tracking 2 characteristics at once. u This supports the idea that each pair alleles segregates independently of other pairs of alleles during gamete formation on non-homologous chromosomes. u Based on outcome of dihybrid cross

Non-Mendelian Inheritance patterns Codominance: The 2 alleles both affect the phenotype in distinguishable ways. u Incomplete Dominance: When the F 1 hybrids have a phenotype somewhere in between the phenotypes of the 2 parental varieties. u

Multiple Alleles u Human ABO blood groups have 3 alleles for this characteristic, in which various combinations produce 4 phenotypes.

Polygenic Inheritance u This creates an additive effect of two or more genes on a single phenotypic character. examples are skin color and height.

Pedigree u Genetic traits can be traced through families by using a pedigree chart.