Question

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where a plant with gray seeds were crossed with another plant with white seeds and the following progeny were produced: 95 gray and 105 white. Assume that the cross above you were interested in determining whether seed color follows a 1:1 ratio. What is the Chi-square value for these data?

1) 0.5
2) 50
3) 0.29
4) 29
5) none of the above

Answer 1

For a cross between a heterozygous gray-seeded plant and a homozygous white-seeded plant in peas, the Chi-square value is 0.5, based on the observed and expected offspring ratios. This confirms that the 1:1 ratio aligns with Mendelian inheritance patterns.

Step-by-step explanation:

The question revolves around Mendelian genetics and specifically the inheritance patterns of pea plants. It involves a Chi-square test to examine whether the observed 1:1 ratio of gray to white seed color in the progeny fits the expected Mendelian ratio for a cross between a heterozygous gray-seeded plant and a white-seeded plant. In this cross, if gray is dominant to white, and we assume that the gray-seeded parent is heterozygous (Gg), crossing with a homozygous recessive white-seeded parent (gg) would indeed yield a 1:1 phenotypic ratio. The total number of progeny is 95 gray + 105 white = 200 seeds. The expected number for each would be half of 200, so 100 gray and 100 white. The Chi-square value is calculated using the formula Χ² = Σ[(observed - expected)²/expected], which yields Χ² = ((95-100)²/100) + ((105-100)²/100) = (25/100) + (25/100) = 0.25+0.25 = 0.5. This is choice (1).