Question

question 4 of 4 > refer to the table. a biologist studying flies made two crosses as shown in the table. parental cross | f₁ genotype | numbers of individuals | xxyy × xxyy | xxyy | 1004 | xxyy | 998 | xxyy | 5 | xxyy | 7 | zzyy × zzyy | zzyy | 796 | zzyy | 793 | zzyy | 215 | zzyy | 220 | what can be inferred about the genes x, y, and z? the genes for all three are on the same chromosome, and y is closer to z than it is to x. the genes for all three are on the same chromosome, and y is closer to x than it is to z. the genes for x and y are on the same chromosome, and y is closer to x than it is to z. the genes for x and y are on the same chromosome, and the gene for z is on a different chromosome. the genes for z and y are on the same chromosome, and the gene for x is on a different chromosome.

Explanation:

1. In genetics, genes on the same chromosome show linkage. Recombinant genotypes are less frequent than parental genotypes. For the cross $XxYy\times xxyy$, the parental - type genotypes ($XxYy$ and $xxyy$) are highly frequent, and recombinant - type genotypes ($Xxyy$ and $xxYy$) are rare, indicating that $X$ and $Y$ are linked (on the same chromosome).
2. For the cross $ZzYy\times zzyy$, the parental - type genotypes ($ZzYy$ and $zzyy$) are more frequent, and recombinant - type genotypes ($Zzyy$ and $zzYy$) are less frequent, indicating that $Z$ and $Y$ are linked.
3. If $X$, $Y$, and $Z$ were all on the same chromosome, we would expect to see some double - crossover and single - crossover combinations involving all three genes in the offspring of a cross involving all three genes. But since we don't have data on a cross involving all three genes simultaneously, and considering the independent frequencies of the $X - Y$ and $Z - Y$ combinations, it is likely that $X$ is on a different chromosome while $Z$ and $Y$ are on the same chromosome.

Answer:

The genes for $Z$ and $Y$ are on the same chromosome, and the gene for $X$ is on a different chromosome.