Punnett Squares Punnett Squares n A Punnett square

Punnett Squares

Punnett Squares n A Punnett square illustrates how the parents’ alleles might combine in offspring. n The top of the Punnett Square one of the parent’s alleles, the side of the Punnett square shows the other parent’s alleles for the trait

n Heterozygous u having dissimilar pairs of alleles for any hereditary characteristic n Homozygous u having identical pairs of alleles for any given pair of heredity characteristics

Mendel’s Laws of Inheritance 1. Law of Dominance: In heterozygous genotypes, dominant alleles hide recessive alleles when both are inherited by an organism. (Hh means the dominant trait will show up in the phenotype) WHY?

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

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

n What is the genotype of a homozygous dominant tall plant? Ø TT n What is the genotype of a homozygous recessive short plant? Ø tt n T TT x tt t t Tt Tt n Genotype 0 % TT 100 % Tt 0 % tt n T Tt Tt Phenotype 100 % tall 0 % short

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

n What is the genotype of a heterozygous brown haired rabbit? Ø Bb n What is the genotype of a homozygous recessive white haired rabbit? Ø bb n B Bb x bb b b Bb Bb n Genotype 0 % BB 50 % Bb 50 % bb n b bb bb Phenotype 50 % brown 50 % white

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

n What is the genotype of a homozygous dominant long haired guinea pig? Ø LL n What is the genotype of a heterozygous long haired guinea pig? Ø Ll n L LL x Ll L l LL Ll n Genotype 50 % LL 50 % Ll 0 % ll n L LL Ll Phenotype 100 % long 0 % short

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

What is the genotype of a heterozygous wrinkly-skinned elephant? Ø Ww n n Ww x Ww W W WW w Ww n Genotype 25 % WW 50 % Ww 25 % ww n w Ww ww Phenotype 75 % wrinkly 25 % smooth

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? n R = round n RR x Rr R R r RR Rr n r = wrinkled Genotype 50 % RR 50 % Rr 0 % rr n R RR Rr Phenotype 100 % round 0 % wrinkled