Question

Question 17 of 25

A cactus can either have long needles (L) or short needles (1). A cactus
grower crosses two cacti. The cross is shown in the Punnett square below.
LL
LL LL
ULI
What is the phenotype ratio for this cross?
O A. One long, three short
B. Four long, zero short
O C. Two long, two short
O D. Three long, one short
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Answer 1

The punnet square in this question is unclear. The punnet square has been attached as an image.

Based on the punnet square, the answer is C. Two long, two short

Step-by-step explanation:

This question involves a single gene coding for needle length in cactus plant. The allele for long needle (L) is dominant over the allele for short needle (l).

According to the question, two cacti were crossed with genotypes Ll and ll respectively. The following allelic combinations of gametes will be produced by each parent

Ll- L and l

ll- l and l

Using these gametes in a punnet square (as seen in the image below), four possible offsprings with genotypes: Ll and ll will be produced in a 1:1 proportion.

Ll offsprings will be phenotypically long-needled while ll offsprings will be phenotypically short-needled. Hence, two long needle offsprings and two short needle offsprings will be produced in this cross.