Dominant allele- trait is always expressed if present - Written as capital letter - Ex. Tall= T Recessive allele- only expressed if no dominant allele is present –(Dominant allele masks this one) - For a particular trait written as the same letter but lower case - Ex. Short= t Dominant and Recessive Alleles
Genotype- the genes you get from your parents –Two letters represent the two alleles –One from mom one from dad – TT, Tt, tt Phenotype- the physical trait, what you look like –Tall short, yellow or green –TT, tt what is the phenotype??
Homozygous - the same alleles for a gene –TT, tt Heterozygous - having different alleles for a gene –Tt
Let’s do some… MONOHYBRID CROSSES! Monohybrid means we are only using ONE TRAIT
STEP by STEP 1.Select a “good” letter to use 2.Write down your “givens” 3.Determine parents and record 4.Set up Punnett Square 5.Determine genotypes & phenotypes of offspring (use percentages or fractions) (use percentages or fractions)
In pea plants being Tall is dominant over being short Cross a Heterozygous Tall plant with a Homozygous Tall plant
Aa x AA Geno = 50% AA 50% Aa Pheno = 100% Tall A A A
In sponges, being blue is dominant over being yellow. Cross a heterozygous blue sponge with a yellow one.
Heterozygous Blue = Bb Recessive Yellow = bb so we cross… Bb x bb
Time for some Monohybrid Crosses on your own! Time for some LOONEY Monohybrid Crosses on your own!