Meiosis, Genetics, & Probability

Biology

How are meiosis & genetics related?

1. Meiosis produces gamete cells.

How are meiosis & genetics related?

2. Diploid cells become haploid cells

How are meiosis & genetics related?

3. Haploid gametes unite to form a diploid zygote.

How are meiosis & genetics related?

4. Zygotes grow into an organism containing:• 50% of the genetic

information from mom• 50% of the genetic

information from dad

What about probability and meiosis and genetics?

• What is probability?• Chance that something

will happen• Examples?• How alleles separate

during meiosis is chance• Therefore, the genes you

receive are by chance

Alleles• Different forms of the same gene

• Ex: Flower color is one gene; it can be in two forms (white or purple)

• Organisms inherit 2 of each allele – one on each homologous chromosome

Punnett Squares

• Used to show probability in genetics

• Predict possible gene (allele) combinations from a cross

• Compare genetic variation from a cross

Terms to know…• Homozygous

Has the same allele for a trait

• HeterozygousHas different alleles for a trait

• PhenotypePhysical appearance of trait

• GenotypeGene makeup (letters) of a trait

Monohybrid crosses

• Monohybrid = one trait being crossed• Example: Pea color (green or yellow)

Practice problems

• In peas, green (G) is dominant to yellow (g).

• What are the phenotypes for the following:• GG?• Gg?• gg?

• Cross a homozygous dominant plant with a heterozygous dominant plant.

• ____ X_____• What is the genotypic

ratio?• What is the

phenotypic ratio?Genotypic ratio: _______________

Phenotypic ratio: ______________

Practice Problem

GG GG

Gg Gg

Genotypic ratio: 2/4 GG; 2/4 Gg

Phenotypic ratio: 4/4 green

G G

G

g