This is to do with genetics and drosophila. There are 3 pairs of characteristics - body colour, eye colour and wing length. The parents are all from pure-breeding lines.

First Cross
P1: male-grey body, normal wings
female-black body, vestigial wings
F1: all females-grey body, normal wings
all males-black body, vestigial wings
F2: 230 flies-grey body, normal wings
15 flies-grey body, vestigial wings
18 flies-black body, normal wings
214 flies-black body, vestigial wings

Second Cross
P1: male-grey body, red eyes
female-black body, white eyes
F1: all females-grey body, red eyes
all males-black body, white eyes
F2: 4720 flies-grey body, red eyes
3372 flies-grey body, white eyes
3389 flies-black body, red eyes
4810 flies-black body, white eyes

Third Cross
P1: male-red eyes, normal wings
female-white eyes, vestigial wings
F1: all females-red eyes, normal wings
all males-white eyes, vestigial wing
F2: 4102 flies-red eyes, normal wings
2164 flies-red eyes, vestigial wings
2169 flies-white eyes, normal wings
4088 flies-white eyes, vestigial

Work out the chromosome map for these genes.
Please help-I have no idea how to do this! Thanks in advance!

To determine the chromosome map for these genes, we need to analyze the results of the crosses and identify the linkage patterns between the genes. The data given includes the phenotypes of the parents, F1 generation, and F2 generation for each cross.

1. First Cross:
P1: male (grey body, normal wings) x female (black body, vestigial wings)
F1: all females (grey body, normal wings) x all males (black body, vestigial wings)
F2:
- 230 flies (grey body, normal wings)
- 15 flies (grey body, vestigial wings)
- 18 flies (black body, normal wings)
- 214 flies (black body, vestigial wings)

From the results, we can see that the traits of body color and wing length are not linked (independent assortment) in this cross because the F1 females produced both possible combinations of traits in the F2 generation. Therefore, we can conclude that the genes for body color and wing length are located on separate chromosomes.

2. Second Cross:
P1: male (grey body, red eyes) x female (black body, white eyes)
F1: all females (grey body, red eyes) x all males (black body, white eyes)
F2:
- 4720 flies (grey body, red eyes)
- 3372 flies (grey body, white eyes)
- 3389 flies (black body, red eyes)
- 4810 flies (black body, white eyes)

Similarly, the traits of body color and eye color appear to be independent and located on separate chromosomes since both cross combinations resulted in the production of all possible trait combinations in the F2 generation.

3. Third Cross:
P1: male (red eyes, normal wings) x female (white eyes, vestigial wings)
F1: all females (red eyes, normal wings) x all males (white eyes, vestigial wings)
F2:
- 4102 flies (red eyes, normal wings)
- 2164 flies (red eyes, vestigial wings)
- 2169 flies (white eyes, normal wings)
- 4088 flies (white eyes, vestigial wings)

When analyzing the results of this cross, we observe that the traits of eye color and wing length display a pattern of linkage. In the F2 generation, the two recombinant phenotypes (red eyes, vestigial wings) and (white eyes, normal wings) are observed at a frequency of 2164 + 2169 = 4333 flies, which is less frequent than the two parental phenotypes (red eyes, normal wings) and (white eyes, vestigial wings) observed at a frequency of 4102 + 4088 = 8190 flies. This difference suggests that the genes for eye color and wing length are likely located on the same chromosome and exhibit some degree of linkage.

To calculate the recombination frequency and determine the gene order, we can use the formula:

Recombination frequency = (Number of recombinant flies / Total number of flies) * 100

In this case, the recombination frequency is approximately (4333 / 8190) * 100 = 52.9%.

Based on this recombination frequency, we can conclude that the gene for eye color is located closer to the centromere than the gene for wing length on the same chromosome. Therefore, the chromosome map for these genes would be:

Centromere - Eye color gene - Wing length gene.

To determine the chromosome map for these genes, we need to analyze the patterns of inheritance from the given crosses. Let's start by identifying the genes and their corresponding traits:

1. Body color: Grey (G) and Black (g)
2. Eye color: Red (R) and White (r)
3. Wing length: Normal (N) and Vestigial (n)

Now, let's analyze each cross and determine the gene order and possible recombination events:

1. First Cross:
P1: male (Gg Nn), female (gg nn)
F1: all females (Gg Nn), all males (gg nn)
F2:
- Grey body, normal wings (GG Nn): 230
- Grey body, vestigial wings (GG nn): 15
- Black body, normal wings (gg Nn): 18
- Black body, vestigial wings (gg nn): 214

From the F2 generation, we can see that 15 flies have the combination of grey body and vestigial wings (GG nn), which indicates a recombination event between the body color and wing length genes. Since these recombinant flies constitute about 6.12% of the total F2 flies, we can conclude that the genes for body color and wing length are relatively close together on the same chromosome.

2. Second Cross:
P1: male (Gg Rr), female (gg rr)
F1: all females (Gg Rr), all males (gg rr)
F2:
- Grey body, red eyes (GG Rr): 4720
- Grey body, white eyes (GG rr): 3372
- Black body, red eyes (gg Rr): 3389
- Black body, white eyes (gg rr): 4810

In this cross, we don't observe any recombinant flies from the F2 generation. This suggests that the genes for body color and eye color are either very close together or located on different chromosomes.

3. Third Cross:
P1: male (Rr Nn), female (rr nn)
F1: all females (Rr Nn), all males (rr nn)
F2:
- Red eyes, normal wings (RR Nn): 4102
- Red eyes, vestigial wings (RR nn): 2164
- White eyes, normal wings (rr Nn): 2169
- White eyes, vestigial wings (rr nn): 4088

Similar to the first cross, we find recombinant flies with the combination of red eyes and vestigial wings (RR nn), which indicates a recombination event between the eye color and wing length genes. These recombinant flies constitute about 34.57% of the total F2 flies.

Now, let's analyze the data from all three crosses together to determine the gene order:

Based on the first and third crosses, we observe recombination events between body color and wing length genes, as well as eye color and wing length genes. Therefore, we can conclude that the Wing Length gene (Nn) is located in the middle.

Using this information and the data from the second cross, we can deduce the order of the genes:

Eye Color (R/r) -> Wing Length (N/n) -> Body Color (G/g)

Therefore, the chromosome map for these genes is:

R - N - G

I hope this explanation helps you understand how to determine the chromosome map based on the given genetic crosses.