Question

In pea plants, purple flowers (P) are dominant over white flowers (p) and tall stems (T) are dominant over short stems (t). Complete a dihybrid cross for parents with the genotypes: PpTT × ppTt and answer the following in complete sentences.

a. describe how you would set up a Punnett square for this cross.
b. List the likelihood of each possible offspring genotype.
Lc. ist the likelihood of each possible offspring phenotype.

Answer 1

A) Cross each gene from the two parents for each trait. B)1/4 possibility for four different genotypes. C) 50%, 25% and 25% likelihood for each possible phenotype.

Step-by-step explanation:

A) To set up a Punnett square for this cross, we need to match the P and p genes with the T and t genes from the other parents and then do the same with the two p genes and two T genes.

B) The likelihoods are for the genotype PpTT - 1/4, PptT - 1/4, ppTT - 1/4, pptT - 1/4.

C) The likelihoods for each phenotype are; 50% for purple flower and tall stems, 25% for white flower and tall stems, 25% for white flower and short steams.

I hope this answer helps.

Answer 2

a. To set up a Punnett square for a dihybrid cross, we need to write the alleles of parent 1 along one side of the square and the alleles of parent 2 along the other side. The alleles must be written in a pair of color of flowers and height of stems.

b. The possible offspring genotypes along with their likelihood are:

PpTT = 4/16

PpTt = 4/16

ppTT = 4/16

ppTt = 4/16

c. The possible offspring phenotypes along with their likelihood are:

Plants with purple flowers and tall stems = 8/16

Plants with white flowers and tall stems = 8/16

Step-by-step explanation:

a. To set up a Punnett square for a dihybrid cross, we need to write the alleles of parent 1 along one side of the square and the alleles of parent 2 along the other side. The alleles must be written in a pair of color of flowers and height of stems. For PpTT, you can write PT, PT, pT, pT. Similarly, for ppTt, you can write pT, pt, pT, pt. Then, you can write the offspring genotypes in the boxes of the Punnett square.

b. To check he possible genotypes, we can draw the Punnett square:

PT PT pT pT

pT PpTT PpTT ppTT ppTT

pt PpTt PpTt ppTt ppTt

pT PpTT PpTT ppTT ppTT

pt PpTt PpTt ppTt ppTt

The possible offspring genotypes along with their likelihood are:

PpTT = 4/16

PpTt = 4/16

ppTT = 4/16

ppTt = 4/16

The likelihood is calculated by counting the number of times the genotype has appeared in the offspring Punnett square and dividing it by the total number of outcomes in the Punnett square i.e. 16.

c. The offspring phenotypes can be depicted by looking at the genotypes. The capital letters represent dominant alleles while small letters represent recessive ones.

Pp means the flower is purple since P represents purple flowers which are dominant over p (white flowers)

pp means the flower is white.

TT means the flower has a tall stem.

Tt also means the flower has a tall stem since T (tall stem) is dominant over t (short stem).

So, PpTT = Plants with purple flowers and tall stems

PpTt = Plants with purple flowers and tall stems

ppTT = Plants with white flowers and tall stems

ppTt = Plants with white flowers and tall stems

There are two phenotypes with an equal likelihood as seen in the Punnett square.

Plants with purple flowers and tall stems = 8/16

Plants with white flowers and tall stems = 8/16