Punnett Squares

Illustrates how the parents’ alleles might combine in offspring. Illustrates how the parents’ alleles might combine in offspring. One parent’s alleles are placed down the side of the square, the other parent’s alleles are placed along the top One parent’s alleles are placed down the side of the square, the other parent’s alleles are placed along the top

Heterozygous : having different alleles for a hereditary character Heterozygous : having different alleles for a hereditary character Homozygous : having identical alleles for a heredity character Homozygous : having identical alleles for a heredity character

Mendel’s Laws of Inheritance 1.Law of Dominance: In heterozygous genotypes, dominant alleles “hide” recessive alleles when both are inherited by an organism.

Mendel’s Laws of Inheritance 1. The Law of Segregation (separation): Each organism has 2 alleles for a trait. Only one allele from each pair will be passed on to the offspring.

Homozygous/Heterozygous Cross a homozygous dominant tall plant with a homozygous recessive short plant. Cross a homozygous dominant tall plant with a homozygous recessive short plant. What letters would you use to represent this cross? Dominant trait = tall Dominant trait = tall Recessive trait = short Recessive trait = short T = tall T = tall t = short t = short Hmzg / Htzg

What is the genotype of a homozygous dominant tall plant? What is the genotype of a homozygous dominant tall plant? Genotype Genotype % TT % Tt % tt  TT TT x tt TT x tt What is the genotype of a homozygous recessive short plant? What is the genotype of a homozygous recessive short plant?  tt t t T TT T Phenotype Phenotype % tall % short Tt

2. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired rabbit. What letters would you use to represent this cross? Dominant trait = brown hair (B) Dominant trait = brown hair (B) Recessive trait = white (b) Recessive trait = white (b)

What is the genotype of a heterozygous brown haired rabbit? What is the genotype of a heterozygous brown haired rabbit? Possible Genotype(s) Possible Genotype(s) % BB % Bb % bb  Bb Bb x bb Bb x bb What is the genotype of a homozygous recessive white haired rabbit? What is the genotype of a homozygous recessive white haired rabbit?  bb b b BbBb Possible Phenotype Possible Phenotype % brown % white bb Bb 0 50

3.. Cross a homozygous dominant long haired guinea pig with a heterozygous long haired guinea pig. What letters would you use to represent this cross? Dominant trait = long hair (L) Dominant trait = long hair (L) Recessive trait = short hair (l) Recessive trait = short hair (l)

What is the genotype of a homozygous dominant long haired guinea pig? What is the genotype of a homozygous dominant long haired guinea pig? Possible Genotype(s) Possible Genotype(s) % LL % Ll % ll  LL LL x Ll LL x Ll What is the genotype of a heterozygous long haired guinea pig? What is the genotype of a heterozygous long haired guinea pig?  Ll L l LL LL Possible Phenotype(s) Possible Phenotype(s) % long % short LLLl LLLl

4. Cross a heterozygous wrinkly elephant with another heterozygous wrinkly elephant. What letters would you use to represent this cross? Dominant trait = wrinkly skin (W) Dominant trait = wrinkly skin (W) Recessive trait = smooth skin (w) Recessive trait = smooth skin (w)

What is the genotype of a heterozygous elephant? What is the genotype of a heterozygous elephant? Possible Genotype(s) Possible Genotype(s) % WW % Ww % ww  Ww Ww x Ww Ww x Ww What is the genotype of a heterozygous elephant? What is the genotype of a heterozygous elephant?  Ww W w WwWw Possible Phenotype(s) % wrinkly % smooth Wwww WWWw

Possible Phenotype(s) % round % wrinkled 5.A plant that is homozygous dominant for round seeds is crossed with a heterozygous plant. What is the probability that the offspring will have wrinkled seeds? RR x Rr RR x Rr R r RRRR RRRr RRRr R = round Possible Genotype(s) Possible Genotype(s) % RR % Rr % rr r = wrinkled