Question

Suppose you perform a monohybrid cross of two pea plants. the plants are heterozygous at the locus for stem height. t is dominant to t. t confers tall plant height. when you count the progeny, you find that there are 188 tall plants and 62 short plants. does this approximate the 3:1 phenotypic ratio caused by mendelian inheritance?

a.no, you would expect there to be more short plants.

b.yes, there are approximately 3 short plants for every tall plant.

c.no, the number of each phenotype is not in the exact ratio of 3:1.

d.yes, there are approximately 3 tall plants for every short plant. submit for grading save and finish later

Answer 1

Yes, there are approximately 3 tall plants for every short plant.

Step-by-step explanation:

The precise ratio of tall to short plants is 188:62 or 3.03:1. This closely approximates the 3:1 ratio predicted as the outcome of a monohybrid cross.

Expected ratios are based on a theoretical population of infinite size, whereas actual populations are finite and often limited in number. Therefore, it is common for the actual numbers of each phenotype from a cross to differ from expectations without violating the expectations of Mendel's Law of Segrergation.

For a theoretical population of 250 individuals, we expect there to be 187.5 tall individuals and 62.5 short individuals. Application of the chi-square goodness-of-fit test to the data gives a chi-square statistic (=Σ (−)2

) of 0.5. Referring to the Chi-Square table of critical values, at 1 degree of freedom, the corresponding p value is between 0.30 and 0.50. Thus, the deviation of the observed data and the expected outcome is statistically insignificant. This does not prove a Mendelian inheritance pattern, but there is insufficient evidence to reject a 3:1 phenotypic ratio.

Answer 2

If T is the dominant allele and expresses the tall phenotype and t is recessive allele for short plants.
The parents are heterozygous Tt
cross between parents
Tt x Tt
offspring TT Tt tT tt
tall plants - TT, Tt and tT - 75%
short plants - tt - 25%
ratio of tall plants to short plants - 0.75 :0.25
0.75/0.25 = 3
In the cross performed , 188 tall : 62 short
188/62 = 3.03
the obtained results follow the 3:1 phenotypic ratio approximately.
answer is b.yes, there are approximately 3 short plants for every tall plant.