Answered

A cactus can either have long needles [tex]\((L)\)[/tex] or short needles [tex]\((I)\)[/tex]. A cactus grower crosses two cacti. The cross is shown in the Punnett square below.

[tex]\[
\begin{tabular}{c|c|c}
& L & I \\
\hline
L & LL & LI \\
\hline
I & LI & II \\
\end{tabular}
\][/tex]

What is the phenotype ratio for this cross?

A. Four long, zero short

B. One long, three short

C. Three long, one short

D. Two long, two short



Answer :

GinnyAnswer
Let's analyze the given problem step-by-step to determine the phenotype ratio for this cross.

First, we interpret the Punnett square provided:

[tex]\[ \begin{array}{c|c|c} & L & I \\ \hline L & LL & LI \\ \hline I & LI & II \\ \hline \end{array} \][/tex]

Each cell in the Punnett square represents a possible combination of alleles from the parent cacti.

1. From the top row and left column, we obtain these combinations:
- LL: Long needles
- LI: Long needles
- LI: Long needles (note that this appears twice, once in the top row, once in the second row)
- II: Short needles

Now, let's count the phenotypes:

- LL results in long needles.
- LI also results in long needles.
- II results in short needles.

So, the counts are:
- Long needles: LL, LI, LI (total 3 times)
- Short needles: II (total 1 time)

This gives us the phenotypes as follows:
- 3 cacti with long needles
- 1 cactus with short needles

Therefore, the phenotype ratio is:

3 long needles : 1 short needle

So, the correct answer is:
C. Three long, one short