Dominant and Recessive Traits

What You'll Learn

Dominant alleles are expressed when present, while recessive alleles are only expressed when two copies are present. A person with one dominant and one recessive allele shows the dominant trait.

Key Words

mitosis
meiosis
trait

Materials Needed

ruler
scissors
microscope (or magnifying glass)
slides

Safety First

Keep small objects away from young children.
Work in a well-ventilated area when using vinegar or other strong-smelling substances.
Dispose of materials properly after the experiment.

Steps

Step 1 — Read

Read and learn: Dominant alleles are expressed when present, while recessive alleles are only expressed when two copies are present. A person with one dominant and one recessive allele shows the dominant trait.

Step 2 — Do

Repeat the experiment two more times for accuracy.

Step 3 — Observe

Note any unexpected results.

Step 4 — Record

Share your findings with the class or a partner.

Check Your Understanding

Question 1

1 of 3

What is a dominant trait?