Why do tall pea plants sometimes have short offspring? Mendel's experiments uncovered the basic rules of heredity.
When an organism has two different alleles for a trait (heterozygous), the dominant allele's trait is expressed, masking the recessive allele.
In pea plants, tall (T) is dominant over short (t). What height will a Tt plant have?
Tall — the dominant T allele masks the recessive t allele
A Punnett square predicts the genotypes and phenotypes of offspring from a genetic cross. Crossing two heterozygous (Tt) plants gives a 1:2:1 genotype ratio and a 3:1 phenotype ratio.
Cross Tt × Tt using a Punnett square. What genotype ratio results?
1 TT : 2 Tt : 1 tt
What phenotype ratio (tall : short) results from a Tt × Tt cross?
3 tall : 1 short
1. In a heterozygous organism, which allele determines the trait that is expressed?
2. Cross TT x tt. What genotype will all the offspring have?
3. What phenotype ratio results from a Tt x Tt cross?
4. What genotype ratio results from a Tt x Tt cross?
5. Why might two tall parent pea plants sometimes produce a short offspring?
6. Who is known as the father of genetics?
7. Is Tt a homozygous or heterozygous genotype?
8. What is the difference between genotype and phenotype?
9. Cross TT x Tt. What fraction of the offspring will be tall?
10. Cross Tt x tt. What phenotype ratio results?