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On an extraterrestrial planet, which had organisms that reproduce with DNA the same way that organisms on Earth do, green little organisms have eyes that are triangular or round. Triangular eyes (T) are dominant to round eyes (t). A Punnett square was made to predict the offspring of two of these extraterrestrials with the genotypes Tt and tt. Use the Punnett square below to answer any questions that follow. According to the Punnett square, what is the probability that an offspring would have triangular eyes? a 0:4 b 1:4 c 2:4 d 3:4 e 4:4

1 answer

To analyze the genetic cross between the two extraterrestrials with the genotypes Tt (triangular eyes) and tt (round eyes), we can use a Punnett square.

The two parents contribute the following alleles:

  • Parent 1 (Tt) can contribute T or t.
  • Parent 2 (tt) can only contribute t.

The Punnett square will be set up as follows:

       T   |   t
      ----------------
 t |    Tt  |  tt  
      ----------------
 t |    Tt  |  tt

From the Punnett square, we can see the possible genotypes of the offspring:

  • Tt (triangular eyes)
  • Tt (triangular eyes)
  • tt (round eyes)
  • tt (round eyes)

Now, let's summarize the results:

  • 2 out of 4 offspring (Tt) will have triangular eyes.
  • 2 out of 4 offspring (tt) will have round eyes.

The probability of an offspring having triangular eyes (Tt) is:

\[ \frac{\text{Number of Tt offspring}}{\text{Total number of offspring}} = \frac{2}{4} = \frac{1}{2} \]

However, looking at the answer options, we can express the probability as:

  • \( 2:4 \) (which simplifies to \( 1:2 \)).

Thus, the answer that corresponds to the number of offspring with triangular eyes compared to the total is:

c. \( 2:4 \)