Punnett square, ratios, percentages. Warm-up Questions: If a person has a genotype of Bb for eye color where brown is dominant to green, what color of eyes will the person have? What is the difference between heterozygous and homozygous? Monohybrid Crosses Punnett square, ratios, percentages.

Monohybrid Crosses Cross involving a single trait. Ex: flower color, eye color, etc.

Punnett Squares Method used to visually analyze crosses and predict offspring or identify parent genotypes. Each parent’s two alleles are placed on the outside of the square. Offspring alleles are determined by crossing the parents alleles.

Genotype Ratios 2:2 Homozygous dominant : heterozygous Genotype ratios are the ratios of the pairs of alleles in the offspring boxes. Written in the form of # of first genotype : # of second : # of third, etc. (#:#:#) 1:2:1 Homozygous dominant : heterozygous : homozygous recessive

Genotype Percentages The percent of offspring that may have the particular allele combination. TT: 50% Tt: 50% Divide the number of the combination with the number of total combinations then multiply by 100. SS: 25% Ss: 50% ss: 25% Ex. 2 of 4 TT = 2÷4 = .5 x 100= 50% TT

Phenotype Ratios Phenotype ratios are the ratios of the different possible phenotypes of the offspring. Written in form of # of first trait : # of second trait. (#:#) Ex. 3:1 Green:White First you must determine the phenotypes of each pair then determine the ratios. 3:1 Green : white

Phenotype Percentages The percent of offspring that may show each trait. Divide the number of the phenotype with the number of total of all then multiply by 100. 75% Green 25% White Ex. 3 of 4 Green = 3÷4 = .75 x 100= 75% Green

New Vocab Hybrid: Cross of the original parents. P Generation: Original parents. F1 Generation: First generation of hybrids. F2 Generation: Cross between two F1 offspring.

What will our Children Look Like?? With a partner, you will be determining what your possible offspring will look like. You will create a Punnett square for each trait: Eye color (Brown is dominant) Hair color (Brown is dominant) Attached or detached earlobes (Attached is dominant) Tongue rolling (Tongue rolling is dominant) Widows peak (Widows peak is dominant) Once your squares are created, you will determine the percentages of each phenotype. Then you will find which phenotype has the highest likelihood of expression. Once this is done, you and your partner will draw the most likely possibility of what your child would look like.

Detailed Instructions on Punnett Squares