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