Unit 4: Mendelian Genetics Section 2- Mendelian Inheritance

I. Probability a. The likelihood that a certain event will occur. b. Used to determine the pattern of inheritance of a trait. c. Formula: (# of times it is expected to occur) (# of times it could occur) a. Ex: Mendel got 705 purple plants and 224 white plants. What is the probability of getting a purple plant? b. 705/929=76%

II. Punnett Squares a. Used to find genotypes and predict outcomes b. Shows every possible combination of mother’s alleles and father’s alleles c. Ex: P=purple allele p=white allele d. Purple is dominant-overpowers white allele e. 75% purple 25% white

III. Determining Genotypes a. Testcross- if genotype is unknown, cross with the homozygous recessive individual. b. RR x rr= Rr (Red x white=red) c. Rr X rr= 50%Rr(red) 50% rr (white) d. rr x rr= rr (white)

IV. Practice  A round pea is crossed with a wrinkled pea. Round is dominant. What are the genotypes of the F1 generation?  What are the genotypes of the F2 generation?

IV. Practice  Green is dominant to yellow in pea pods. Cross a heterozygous green with a yellow plant. Give the genotypic and phenotypic ratios.

V. Example  Mendel bred 7324 plants. He got 5474 round peas and 1850 wrinkled.  Which is the dominant trait?  What is the probability of getting the dominant phenotype?  What are the genotypes and phenotypes of the parents?