SECTION 11.2Genetic Crosses

I. Genotype and Phenotype

1. Genotype: genetic makeup of an organism

a. Alleles that give the organism its traits

b. EX: Tall: Short:

2. Phenotype: physical characteristics shown because of genotype

a. EX:

I. Genotype and Phenotype

3. Homozygous: alleles that are the same for a characteristic

a. EX: Tall: Short:

4. Heterozygous: alleles that are different for the same characteristic

a. EX: Tall:

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

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

Ex: Flower Color Dominant: Purple

Recessive: White

Genotype:

Phenotype:

b. Homozygous vs. Heterozygous

Ex: Flower Color Dominant: Purple

Recessive: White

Genotype:

Phenotype:

c. Heterozygous vs Heterozygous

Ex: Flower Color Dominant: Blue

Recessive: White

Genotype:

Phenotype:

IV. Dihybrid Crosses

1. Cross organisms with 2 different traits

2. Possible Crossesa) Homozygous x Homozygous

b) Heterozygous x Heterozygous

a. Homozygous x Homozygous

Ex: Flower Color Dominant: Purple

Recessive: White

Flower Height Dominant: Tall

Recessive: Short

b. Heterozygous x Heterozygous

Ex: Flower Color Dominant: Blue

Recessive: White

Flower Height Dominant: Tall

Recessive: Short

V. Patterns of Inheritance1. Complete Dominance: Dominant trait completely masks recessive trait

V. Patterns of Inheritance

Incomplete Dominance:

Heterozygote has phenotype intermediate btwn phenotypes of two homozygotes

-

Incomplete DominanceFlower Color: Dominant: Red (R)

Recessive: White (r) Intermediate: Pink

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 )

Multiple AllelesBlood Type: Dominant: Type A and B

Recessive: Type O

Genotype:

Phenotype:

VIII. Sex Chromosomes

•Sex Determination:

–Example:

–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)

Genotype:

Phenotype:

X. Pedigree Charts

1. Autosomal Dominant

2. Autosomal Recessive: Heterozygotes carry the recessive allele

but exhibit the wildtype phenotype