Teacher resources and professional development across the curriculum
Teacher professional development and classroom resources across the curriculum
An English geneticist, Reginald Punnett, devised an easy way to calculate the probability that a certain trait will be inherited. It involves what is now called a Punnett square. In order to use a Punnett square, it helps to know some common terminology:
Allele: The alternative forms of a gene, like the "tall" and "short" versions of the gene for height in garden peas.
Dominant: An allele that produces the visible or measurable trait in an organism and is expressed over recessive genes. Dominant alleles are represented by a capital letter ("T").
Genotype: The specific combination of alleles possessed by an individual. Example: "homozygous dominant," which means possessing two copies of the dominant allele.
Homozygous: Possessing two copies of the same allele, both dominant or both recessive. Example: "TT" or "tt."
Heterozygous: Possessing two different alleles. Example: "Tt."
Phenotype: The detectable or measurable characteristic of an organism. Example: tall. The phenotype can, but doesn't always, indicate the genotype.
Recessive: An allele that is expressed only when the dominant allele is not present. Recessive alleles are represented by a lowercase letter ("t").
Trait: A feature or characteristic of an organism that can be tested for or observed.
Problem: Cystic Fibrosis
Fill out this Punnett square with the correct letters if both parents are carriers of the cystic fibrosis gene.
|Next: Sex Linkage|