Pedigrees

Front

What is a pedigree?

Back

A pedigree is a diagram that shows the occurrence and appearance of phenotypes of a particular gene or organism and its ancestors.

Front

What does it mean if a trait is dominant?

Back

A dominant trait is one that will appear in the phenotype even if only one allele is present.

Front

What does it mean if a trait is recessive?

Back

A recessive trait only appears in the phenotype if two copies of the recessive allele are present.

Front

What does a filled square represent in a pedigree?

Back

A filled square represents an affected male.

Front

What does a filled circle represent in a pedigree?

Back

A filled circle represents an affected female.

Front

What does a half-filled symbol represent in a pedigree?

Back

A half-filled symbol indicates that the individual is a carrier (heterozygous) for a trait.

Front

What is the genotype for a straight thumb?

Back

The genotype for a straight thumb can be either TT (homozygous dominant) or Tt (heterozygous).

Front

What is the genotype for hitchhiker's thumb?

Back

The genotype for hitchhiker's thumb is tt (homozygous recessive).

Front

What is the significance of the letters in a genotype?

Back

The letters represent alleles, where uppercase letters denote dominant alleles and lowercase letters denote recessive alleles.

Front

How can you determine if an individual is a carrier for a recessive trait?

Back

An individual is a carrier if they have one dominant allele and one recessive allele (heterozygous genotype).