Question

Four homozygous recessive mutant lines of Drosophila (labeled 1 through 4) showed abnormal leg coordination, which made their walking highly erratic. These lines were intercrossed; the phenotypes of the F1 flies are shown in the following grid, in which "+" represents normal walking and "-" represents abnormal walking. For example, when Line 1 flies are crossed with other Line 1 flies, the progeny is mutant (in red). However, when Line 2 flies are crossed with Line 1 flies, the progeny are wild type / normal (in green). | | Line 1 | Line 2 | Line 3 | Line 4 | | :--- | :--- | :--- | :--- | :--- | | Line 1 | - | + | + | + | | Line 2 | | - | - | + | | Line 3 | | | - | + | | Line 4 | | | | - | 1.) What type of test does this analysis represent? Hint: (it starts with C:)) 2.) Why is this important that all four of the mutations are recessive? Hint: will the test work if one of the mutations is dominant? Why, or why not? 3.) How many different genes were mutated in creating those four lines? In other words, do any of these lines contain mutations in the same gene? 4.) Do these data tell us the total number of genes involved in leg coordination in Drosophila? Why, or why not?

          Four homozygous recessive mutant lines of Drosophila (labeled 1 through 4) showed abnormal leg coordination, which made their walking highly erratic. These lines were intercrossed; the phenotypes of the F1 flies are shown in the following grid, in which "+" represents normal walking and "-" represents abnormal walking. For example, when Line 1 flies are crossed with other Line 1 flies, the progeny is mutant (in red). However, when Line 2 flies are crossed with Line 1 flies, the progeny are wild type / normal (in green).

| | Line 1 | Line 2 | Line 3 | Line 4 |
| :--- | :--- | :--- | :--- | :--- |
| Line 1 | - | + | + | + |
| Line 2 | | - | - | + |
| Line 3 | | | - | + |
| Line 4 | | | | - |

1.) What type of test does this analysis represent? Hint: (it starts with C:))
2.) Why is this important that all four of the mutations are recessive? Hint: will the test work if one of the mutations is dominant? Why, or why not?
3.) How many different genes were mutated in creating those four lines? In other words, do any of these lines contain mutations in the same gene?
4.) Do these data tell us the total number of genes involved in leg coordination in Drosophila? Why, or why not?

Four homozygous recessive mutant lines of Drosophila (labeled 1 through 4) showed abnormal leg coordination, which made their walking highly erratic. These lines were intercrossed; the phenotypes of the F1 flies are shown in the following grid, in which "+" represents normal walking and "-" represents abnormal walking. For example, when Line 1 flies are crossed with other Line 1 flies, the progeny is mutant (in red). However, when Line 2 flies are crossed with Line 1 flies, the progeny are wild type / normal (in green).

| | Line 1 | Line 2 | Line 3 | Line 4 |
| :— | :— | :— | :— | :— |
| Line 1 | - | + | + | + |
| Line 2 | | - | - | + |
| Line 3 | | | - | + |
| Line 4 | | | | - |

1.) What type of test does this analysis represent? Hint: (it starts with C:))
2.) Why is this important that all four of the mutations are recessive? Hint: will the test work if one of the mutations is dominant? Why, or why not?
3.) How many different genes were mutated in creating those four lines? In other words, do any of these lines contain mutations in the same gene?
4.) Do these data tell us the total number of genes involved in leg coordination in Drosophila? Why, or why not?

Added by Keith W.

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