Genetics College Biology
Gregor Mendel
• Mid 1800’s, Austrian monk.
• Introduced probability to genetics
• Mated pea plants
Cross-pollination
Produce seeds that have two different plants as parents
Traits
• Specific characteristic
Genes
• Chemical factors that determine traits
Alleles
• Different forms of the gene
The Principle of Dominance
• States that some alleles are dominant and others are recessive.
Law of Segregation
• Alleles for each trait are segregated from each other during the formation of sex cells, gametes.
Probability
• Likelihood that a particular event will occur.
Punnett Squares
• Used to predict and compare the genetic variations that will result from a cross
Homozygous
Two identical alleles
- Dominant: TT
- Recessive: tt
Heterozygous
• Two different alleles
Phenotype
• Physical characteristics
Genotype
• Genetic makeup
Law of Independent Assortment
• Genes of different traits can segregate independently of each other
• Dihybrid cross
Incomplete Dominance
• Heterozygous phenotypes are a mix of the two homozygous parents
Codominance
• Both alleles contribute to the phenotype
Multiple Alleles: more than two alleles
Polygenic Traits
• Having many genes that determine a trait
• Skin color, eye color