Probability and Heredity

1. Probability and Heredity *Students know plant and animal cells contain many thousands of different genes and typically have two copies of every gene. The two copies of the gene may or may not be identical, and one may be dominant in determining the phenotype while the other is recessive

2. Principals of Probability • Probability • Is a number that describes how likely it is that a certain event will occur

3. Probability and Genetics Punnett Square Genetic Cross Is a chart that shows all the possible combinations of alleles that can result from a genetic cross The allele that each parent will pass on is based on probability

4. Predicting Probabilities • The possibility of TT is ¼ or 25% • The possibility of Tt is 2/4 or 50 % • The possibility of tt is ¼ or 25% • http://www.athro.com/evo/gen/punexam.html

5. Phenotypes and Genotypes • Phenotype • genotype • Physical appearance or Visible traits • Genetic makeup or allele combination

6. Genotypes • Homozygous • heterozygous • An organism has two identical alleles for a trait. - TT or tt • An organism has two different alleles for a trait.- Tt

7. Codominance • Codominance • The alleles are neither dominant nor recessive. As a result both alleles are expressed in the offspring