The following cross (colored (C) and colorless (c) kernels; green (G) and yellow

Question

The following cross (colored (C) and colorless (c) kernels; green (G) and yellow (g) plants) resulted in the following F2 genetic data from a cross between homozygous plants that were colored and green x colorless and yellow:

Colored green (C_G_ )- 88
Colored yellow (C_gg-) 12
Colorless green (ccG_)- 8
Colorless yellow (ccgg)- 92

The hypothesis is that the two genes are unlinked, that is on separate chromosomes. Perform a ?2 test and determine the P value. Do the data support the hypothesis? Why or why not?

Explanation / Answer

When colored green and colorless yellow are crossed the F2 should have a genotypic ratio of 9:3:3:1. The total number of offspring is 200. The expected number of offspring per genotype is: 9/16 x 200 = 112.5 3/16 x 200 = 37.5 1/16 x 200 = 12.5 --------------------------------- These values are totally different from the values in the data. In addition as most of the offspring have the parental genotypes of colored green and colorless yellow, the genes have to be linked. ------------------------------- The difference in values from the expected and the observed values is very high. For each of the genotypes, the difference in values is around 25. As the probability value is above 5, the null hypothesis is rejected and the population is not in Hardy Weinberg equilibrium. ------------------------------- The data does not support the hypothesis that the genes are unlinked and are present on different chromosomes. When linked genes are crossed, the majority of the offspring has the parental genotypes and a small ratio of recombinant genotypes. As seen in the data, the parental genotypes in the offpsring account for 90% of the offspring. Only 10% of the offspring show recombinant genotypes not seen in the parents. On this basis we can say that the distance between the two genes is 10 m.u.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.