Alleles Dominant Allele Only 1 copy of the

Alleles Dominant Allele • Only 1 copy of the allele is needed to express the trait Recessive Allele • Individual must have both copies of the allele to express the trait

How to Choose Letters to Represent Alleles • Choose the first letter of the dominant trait to represent the allele • Dominant is capitalized and Recessive is lower case Example: Pod Colour • Remember green is dominant over yellow = represents the dominant green allele G = represents the recessive yellow allele g

Genotype: • The combination of the 2 alleles an organism has Question: Genotype What are three possible genotypes for pod colour? GG Gg gg

Phenotype: • The expression of a trait based on the genotype • With a Heterozygous genotype, only the dominant trait will be expressed Genotype Phenotype Question: What will the phenotypes be for the three combinations of alleles? GG Green Gg Green gg Yellow

Steps to Follow: 1. Find out which allele is dominant 2. Assign letters to each allele using the first letter of the dominant allele. 3. Find all possible genotypes. 4. Figure out which phenotype for each genotype.

Example: The gene for seed shape has 2 alleles. Round is dominant over Wrinkled 1. What are three possible genotypes? • RR, Rr, rr 2. What shape would the seeds be if the plant has 1 round and 1 wrinkled allele? • Round 3. What phenotype would the seeds have if the plant was homozygous recessive? • Wrinkled

Punnet Squares • Used to determine the genotypic and phenotypic probabilities • It is similar to map grids, and the Battleship game • D-3 “You sunk my Battleship!”

Punnet Squares 1. Place one parent’s genotype on the top of the grid. 2. Place the other parent’s genotype on the left side. 3. Fill in the grid with both parents’ alleles for each box. T t T TT Tt tt

Punnet Squares Now try another one! Y y y Yy yy