PUNNETT SQUARE PRACTICE

DOMINANT VS. RECESSIVE Dominant - Masks the other trait; the trait that shows if present  Represented by a capital letter Recessive – An organism with a recessive allele for a particular trait will only exhibit that trait when the dominant allele is not present; Will only show if both alleles are present  Represented by a lower case letter R r

GENOTYPE VS. PHENOTYPE Genotype – The genetic makeup of an organism; The gene (or allele) combination an organism has.  Example: Tt, ss, GG, Ww Phenotype – The physical characteristics of an organism; The way an organism looks  Example: Curly hair, straight hair, blue eyes, tall, green

HOMOZYGOUS VS. HETEROZYGOUS Homozygous – Term used to refer to an organism that has two identical alleles for a particular trait (TT or tt) Heterozygous - Term used to refer to an organism that has two different alleles for the same trait (Tt) RR Rr rr

Black colored fur is the dominant trait. We will use the Punnett’s Square to determine the offspring of guinea pigs. The offspring will either be black or white.

Generation 1 BB b b In this case we have a dad with black fur and a mother with white fur. Because black is the dominant gene, we write it with a capital ‘B’.

Tongue Curling Tt T T Copy into your notebook and complete the Punnett’s Square. What percentage of offspring will be able to curl their tongue?

Tongue Curling Tt T T 100% percent of offspring will be able to curl their tongues. TTTt TTTt

R = red r = white Cross a homozygous white flower with a heterozygous red flower. What percentage will be white? What percentage will be red?