Lab Report: Genetic Crosses 2

Question

Part 1: Incomplete Dominance—Predicting Flower Color in Snapdragons

Snapdragons are popular garden plants that produce brightly colored flowers. When a plant that is homozygous for white flowers is crossed with a plant that is homozygous for red flowers, all offspring are pink. Snapdragons are an example of a plant that exhibits an inheritance pattern called incomplete dominance.

1. Determine the genotype of each parent plant and write them below. Use W to indicate the allele for white flowers and w to indicate the allele for red flowers.

Genotype of homozygous parent plant with white flowers:

Genotype of homozygous parent plant with red flowers:

2.Next, think about the gametes each parent plant will produce. List the allele in each gamete.

Parent plant with white flowers:

Gamete 1:

Gamete 2:

Gamete 3:

Gamete 4:

Parent plant with red flowers:

Gamete 1:

Gamete 2:

Gamete 3:

Gamete 4:

3.  The two parent plants are the P generation, or parent generation. Create a Punnett square to show their offspring, the F1 generation.

4.  What pattern do you notice in the genotypes of the F1 generation snapdragons?

5.  What are the phenotypes of the F1 generation snapdragons?

Answer 1

1. Determine the genotype of each parent plant and write them below. Use W to indicate the allele for white flowers and w to indicate the allele for red flowers.

Genotype of homozygous parent plant with white flowers: WW

Genotype of homozygous parent plant with red flowers:ww

The pink offspring would be Ww. Generally, you would learn that the WW or Ww would be white, but because the W isn't 100% dominant over w, the flower is pink. Basically, the plant requires two copies of W to make enough red pigment to appear red.