Objectives 11.2 Applying Mendel’s Principles -Explain how geneticists use the Punnett square. -Examine the principle of independent assortment. -Analyze how Mendel’s principles apply to all organisms.

Probability Probability is the likelihood that a particular event will occur.

Using Segregation to Predict Outcomes The principles of probability can be used to predict the outcomes of genetic crosses. Consistently , when crossing heterozygotes for a certain trait the 3:1 ratio came up in Mendel’s experiments.

Homozygous or Heterozygous ~ Organisms that have two IDENTICAL alleles for a particular gene -TT or tt - are said to be HOMOZYGOUS. ~Organisms that have two DIFFERENT alleles for a trait – Tt – are HETEROZYGOUS.

Genotype and Phenotype Every organism has genetic AND physical characteristics. The phenotype is the physical traits. The genotype is the genetic makeup.

Using Punnett Squares Punnett squares can be used to predict both the genotype and the phenotype of a particular organism, when the alleles are known, using probability.

Monohybrid or Dihybrid Cross??? When it involves two different genes, the experiment is known as a dihybrid cross. Single-gene crosses are monohybrid crosses.

True or False The principles of probability can explain the numerical results of Mendel’s experiments. _________________________ The probability that a gamete produced by a pea plant heterozygous for stem height (Tt) will contain the recessive allele is 100%. _________________________ A trait in an unidentified plant is controlled by one gene that has two alleles. One allele is dominant over the other. According to Mendel’s principles, one fourth of the offspring made from a cross between two heterozygous plants will show the recessive trait. _________________________

Answers The principles of probability can explain the numerical results of Mendel’s experiments. True The probability that a gamete produced by a pea plant heterozygous for stem height (Tt) will contain the recessive allele is 100%. False, 50% A trait in an unidentified plant is controlled by one gene that has two alleles. One allele is dominant over the other. According to Mendel’s principles, one fourth of the offspring made from a cross between True