Understanding Inheritance Ch.5 Sect. 2

What Controls Traits? 2 factors (one from each parent) control each trait. 1 factor came from the egg and one factor came from the sperm. Chromosomes contain genetic information that controls traits.

Genes and Alleles Each chromosome can contain info for hundreds or thousands of traits. Gene is a section on a chromosome that has genetic information for one trait. Ex. Flower color. Genes can be the same or different. Alleles are the different forms of a gene. Ex. 2 purple or 2 white alleles or one from each.

Genotype and Phenotype Phenotype is how the trait is expressed. Ex. Blue eye color Genotype: are the two alleles that control the phenotype of the trait. In genotypes: dominant alleles are represented by capital letters and recessive traits are represented by lower case letters. Ex: Purple (P) is dominant, white (p) is recessive.

Homozygous and Heterozygous Homozygous is when the two alleles of a gene are the same. Ex: PP (homozygous dominant) or pp (homozygous recessive). Heterozygous is when the two alleles of a gene are different. Ex: Pp (heterozygous dominant).

Modeling Inheritance Punnett Squares is a model used to predict possible genotypes and phenotypes of offspring.

Pedigrees Shows phenotypes of genetically related family members. Also help determine genotypes

Complex Patterns of Inheritance Incomplete Dominance happens when the offspring’s phenotype is a combination of parents’ phenotypes. Ex. Pink Camellia Plant Codominance is when both alleles can be observed in a phenotypes.

Multiple Alleles & Polygenic Inheritance Some genes have multiple alleles. Ex. Human Blood Type (3 different alleles). Those three alleles can combine to form one of four blood types. (A, B, AB, O). Polygenic Inheritance occurs when multiple genes determine the phenotype of a trait. Ex. Eye Color

Genes and the Environment The environment can also affect phenotypes. Ex. Hydrangea’s color can be affected by the type of soil it grows in. For humans, the lifestyle the live can affect the phenotype. Ex. Heart disease