SECTION 11.2 Genetic Crosses

I. Genotype and Phenotype 1.Genotype: genetic makeup of an organism a.Alleles that give the organism its traits b.EX: Tall: TT, TtShort: tt 2.Phenotype: physical characteristics shown because of genotype a.EX: Tall or short 3.Homozygous: alleles that are the same for a characteristic a.EX: Tall: TTShort: tt 4.Heterozygous: alleles that are different for the same characteristic a.EX: Tall: Tt

II. Probability 1.Probability: the chance of a specific trait occur or not occurring in an organism 2.Probability= # of times trait is expected to happen # of opportunities for an trait to happen 3.Example: Tall peas: 150 Short peas: 50 Probability of Short Peas: 25% = 50/200

III. Monohybrid Crosses 1.Monohybrid: crossing one trait from two different organisms 2.Use a Punnett Square 3.Possible Crosses: a.Homozygous x Homozygous b.Homozygous x Heterozygous c.Heterozygous x Heterozygous

a. Homozygous vs. Homozygous ______ vs. _______ Ex: Flower Color Dominant: Purple: AA, Aa Recessive: White: aa Genotype: Phenotype:

b. Homozygous vs. Heterozygous ________ vs. _______ Ex: Flower ColorDominant: Purple: AA, Aa Recessive: White: aa Genotype: Phenotype:

c. Heterozygous vs Heterozygous _________ vs. _______ Ex: Flower ColorDominant: Blue: BB, Bb Recessive: White: bb Genotype: Phenotype:

IV. Dihybrid Crosses 1.Cross organisms with 2 different traits 2.Possible Crosses a)Homozygous x Homozygous b)Heterozygous x Heterozygous

a. Homozygous x Homozygous ________ x______ Ex: Flower ColorDominant: Purple: AA, Aa Recessive: White: aa Flower HeightDominant: Tall: TT, Tt Recessive: Short: tt

b. Heterozygous x Heterozygous Ex: Flower ColorDominant: Blue Recessive: White Flower HeightDominant: Tall Recessive: Short

V. Patterns of Inheritance 1.Complete Dominance: Dominant trait completely masks recessive trait 2.Incomplete Dominance: Heterozygote has phenotype intermediate btwn phenotypes of two homozygotes - Possible to mix a red and white flower to make pink

Incomplete Dominance Flower Color: Dominant: Red (R): RR Recessive: White (r): rr Intermediate: Pink: Rr Genotype: Phenotype:

VI. Codominance Codominance: Phenotype of the heterozygote includes the phenotypes of both homozygotes 1.No one allele is dominant, recessive, or blends 2.Example: animal fur color, blood types

VII. Multiple Alleles Multiple Alleles – More than two allele varieties are present within a group of individuals a)Varies genotype and phenotypes b)Example: Blood Type ( ABO Group )Blood Type

Multiple Alleles Blood Type: Dominant: Type A: I A I A, I A i Type B: I B I B, I B i Type AB: I A I B Recessive: Type O: ii Genotype: Phenotype:

VIII. Sex Chromosomes Sex Determination: – Example: Male: XY Female: XX – Disorders/Syndromes: Turner Syndrome: 1 X & 0 Y (female) Klinefelter Syndrome: many X & 1-2 Y (male) Poly-X females: 3 X (female)

IX. Sex-Linked Characteristics Determined by genes located on ___________ – Most are ____ -linked – Example: Color Blindness (X-linked recessive)Color Blindness Genotype: Phenotype:

X. Pedigree Charts

1. Autosomal Dominant

2. Autosomal Recessive: Heterozygotes carry the recessive allele but exhibit the wildtype phenotype