Two-Factor Cross: In pea plants, the "tall" allele is dominant over the short one, and yellow is dominant over green. Cross two plants that are hybrid for both traits. Show the Punnet Square.

Question

I don't understand what it means by, "hybrid". Any help is appreciated. Thanks.

Answer 1

A hybrid pea plant is heterozygous, meaning it has one of each allele. An allele just means a specific version of a gene. For example, the gene for height in pea plants could be a "tall" allele or "short" allele. The gene for pea plants' color could be "yellow" allele or "green" allele. Let's just do a little shorthand notation and put T for "tall" allele because they told us it is dominant and t for "short" allele because it is...well recessive. So then the possible genotypes could be Tt or TT or tt. Tt (2 different alleles) is then said to be heterozygous. TT (2 identical alleles) and tt (2 identical alleles) are then said to be homozygous. Tt being heterozygous (having 2 different alleles) is a hybrid. Another way to think of it is a hybrid car, a car that runs on gas and electricity. Tesla, which runs only on electricity is NOT a hybrid, so TT (having tall genes only in the mix) and tt (having short genes only in the mix) are NOT hybrids. Please let me know if that was clear to you.

Answer 2

Tall = T

Short = t

Yellow = Y

Green = y

It means that the pea plants have all of these so TtYy x TtYy

Hope this helps