Genetics

Mendel’s Laws of Heredity Heredity Traits allele

Genetics Terms purebred hybrid

Genetics Terms Homozygous Homozygous recessive Homozygous dominant Heterozygous

Genetics Terms dominant recessive Tall = dominant TT or Tt dwarf = recessive tt ONLY there can never be heterozygous recessive!

Genetics Terms phenotype genotype Phenotype = Tall Genotype = TT

Genetics Terms Parental generation P1 parents First filial generation F1 offspring Monohybrid cross mating between individuals focussed on one trait

Steps to solving Punnett Squares

Example # 1 In a certain species of mouse, pointed ears are dominant over round ears. Predict the genotypes and phenotypes of a cross between two hybrid pointed-eared mice.

Write a key. Include both alleles. P= pointed ears p= round ears

Write a “cross” to show the parents’ genotypes. Parent one= Pp Parent two= Pp

Write the parents’ genotypes (letters) around the outside of the square. P p PpPp Parent One Parent Two

Fill in the square- copy letters down and across. P p PpPp Parent One Parent Two PP Pp pp

Write the percentage chance for the offspring’s genotypes P p PpPp Parent One Parent Two PPPp pp 25%= PP (Homozygous Dominant) 50%= Pp (Heterozygous) 25%= pp (Homozygous Recessive)

Write the percentage chance for the offspring’s phenotypes 75% chance of having Pointed Ears

Try it yourself In a certain species of dog, a black nose is dominant over a pink nose. Predict the genotypes and phenotypes of a cross between a purebred dominant male dog and a purebred recessive female.

Here are the Steps: 1. Write a key. Include both alleles. 2. Write a “cross” to show the parents’ genotypes. 3. Write the parents’ genotypes (letters) around the outside of the square. 4. Fill in the square- copy letters down and across. 5. Write the percentage chance for the offspring’s genotypes 6. Write the percentage chance for the offspring’s phenotypes