Punnett Squares

Punnett Squares

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; 

• Recessive – lower case

Practice

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• —TT - Represent offspring with straight hair

  —Tt - Represent offspring with straight hair

  —tt - Represents offspring with curly hair

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Multiple Choice

Which of the following genotypes is homozygous dominant?

• aa

• Aa

• AA

Multiple Choice

Which of the following alleles is purebred recessive?

• Tt

• tt

• TT

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

Homozygous vs. Heterozygous

• Homozygous – Term used to refer to an organism that has two identical 

• Heterozygous - Term used to refer to an organism that has two different 

Multiple Choice

What type of Genotype is this: DD?

• Homozygous

• Heterozygous

Multiple Choice

What type of Genotype is this: Aa?

• Homozygous

• Heterozygous

Multiple Choice

What type of Genotype is this: AA?

• Homozygous

• Heterozygous

Punnett Squares

• —Punnett Square – Diagram showing the gene combinations that might result from a genetic cross

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Multiple Choice

How chance the offspring born from this cross will have a homozygous dominant genotype?

• 25%

• 50%

• 75%

• 100%

Multiple Choice

Fill in the Yellow Box

• Bb

• BB

• bb

Multiple Choice

Fill in the Yellow Box

• AA

• Aa

• aa

Multiple Choice

Which of the following is a heterozygous genotype?

• Gg

• UU

• pp

Multiple Choice

Which of the following is a Homozygous Dominant Genotype?

• Yy

• XX

• zz