Imagine you are looking out at a field of sunflowers. 774 plants are tall (T) and 226 plants are short (t). Based on Mendel's original work, what can you say about the genotypes of the parents of this field of flowers?

Question

Responses
A Parent 1 = Tt; Parent 2 = TtParent 1 = Tt; Parent 2 = Tt
B Parent 1 = TT; Parent 2 = ttParent 1 = TT; Parent 2 = tt
C Parent 1 = TT; Parent 2 = TtParent 1 = TT; Parent 2 = Tt
D You cannot determine anything about the parents without seeing them.

Answer 1

To analyze the genotypes of the parents based on the observed phenotypic ratios in the sunflower field, we can start by noting the tall (T) and short (t) plant distributions:

• Tall plants (T): 774
• Short plants (t): 226

From this, we can calculate the total number of plants:

Total = 774 (tall) + 226 (short) = 1000

The observed phenotypic ratio of tall to short plants is:

• Tall : Short = 774 : 226

To simplify this ratio, divide both numbers by 2:

• 774 / 2 = 387
• 226 / 2 = 113

This gives us a simplified ratio of approximately 387:113, which is close to a 3:1 ratio.

According to Mendelian genetics, a 3:1 phenotypic ratio typically results from a monohybrid cross where both parents are heterozygous (Tt). The expected phenotypic proportions from Tt x Tt would be:

• TT: 1
• Tt: 2
• tt: 1

This gives a total ratio of 3 tall (TT or Tt) to 1 short (tt).

Thus, based on the phenotypic ratio observed in this sunflower field, the most reasonable conclusion about the genotypes of the parents is:

A. Parent 1 = Tt; Parent 2 = Tt