Gregor Mendel: The Father of Genetics
Gregor Mendel was a geneticist who contributed some of the first and most important clues
to the study of heredity. As an Austrian monk in the 1860s, Mendel worked with garden pea
plants and discovered how traits were passed from one generation to the next.
These were the seven traits that Mendel studied on the pea plants:
He was able to determine which traits were dominant and recessive by crossing different
plants and observing the offspring that were made. (Crossing refers to the “mating” of the
plants by manipulating their pollination.)
Practice Problems with Mendel’s peas:
Use a Punnett Square to determine the possible genotypes and phenotypes of the offspring
for each cross.
1. A homozygous dominant plant for flower color is crossed with a homozygous recessive
plant for flower color.
2. Two plants that are heterozygous for flower color are crossed.
3. Tall (T) is dominant to short (t). If a heterozygous pea plant is crossed with a
homozygous recessive pea plant, what is the chance that they will produce short plants?
4. In the P (parental) generation, Mendel crossed two plants that were purebred for pea
color. (A purebred is an organism that received the same genetic traits from both of its
parents. So, YY x yy.) What color peas will there be in the F1 generation? (F1 is the
generation that is produced from a cross in the P generation.)
5. If two plants from the F1 generation from question #4 are crossed, what are the possible
pea colors for the F2 generation?
6. Round pea shape is dominant to wrinkled pea shape. Cross a plant that is heterozygous
for pea shape with one that is homozygous recessive for pea shape.
7. In the F1 generation, 6 purple-flowered plants and one white-flowered plant grew. What
must have been the genotypes of the P generation?
8. The flowers on a pea plant can either be axial (in the middle of the stem) or terminal (at
the end of the stem). What are the possible genotypes and phenotypes of the offspring
when a plant that is heterozygous for flower position is crossed with a plant that is
homozygous dominant for flower position?