4.4 Punnett Squares

What is a Genotype?

Genotype genes that are passed on from parents to offspring. Showed using Letters LL, Ll, ll WW, Ww, ww RR, Rr, rr

What is a Phenotype?

Phenotype trait that is seen Think pheno “photo” Examples Blue eyes Widows peak Hitch hackers thumb Curly hair

What is an Allele?

Allele Different version of the same gene We usually refer to it as either the dominant allele or the recessive allele Example Allele for straight hair (recessive) Allele for curly hair (dominant)

What is a Dominant Allele?

Dominant Allele Genotype – Capital Letter (W) Phenotype – Guaranteed to see it

What is a Recessive Allele? Genotype – Lower case letter (a) Phenotype – Will not be seen unless both alleles are recessive (aa)

What does Homozygous mean?

Homozygous Both Alleles are Alike Homo = Same Examples: aa AA WW ww

What does Heterozygous mean? Alleles are opposite Hetero = different Examples Hh Aa Ee Gg Yy

How to fill in a Punnett Square

Review

Sample Problem: Cross a male chicken who is Heterozygous for his blue color with a female chicken who is homozygous recessive black.

Cross a male chicken who is Heterozygous for his blue color with a female chicken who is homozygous recessive black. Genotype Results: 50% Bb 50% bb

What does the Phenotype results look like for this punnett square?

2 out of 4 (50%) Blue Chickens 2 out of 4 (50%) Black Chickens