Investigators crossed a strain of heterozygote flies for the recessive mutations, lobe (eye) smooth

The highest number of flies are same the parental genotypes. The least number of flies have double crossing over. So that you can compare these phenotypes and you will understand that which gene is intermediate.

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So in this question starw body character is intermediate

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After that you must find the flies which have single crossing over. You can bring together two phenotypes that the phenotype which has a character and other phenotype has not this character.

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So the first group is the phenotypes which are 248 and 262. The second group is 73 and 65

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At that, all of them we will do are mathematic.

We have got 2444 flies.

We know that straw body character is intermediate. Smoot abdomen's distance is (248+262+9+12)/2444= 531/2444 is about 0.2172. And now we multiply this wtih 100 to find provision of the distance in cantimorgan(cM). It is about 22 cM

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We must do same process to find lobe character's distance.

(65+73+9+12)/2444= 531/2444 is about 0.065. And we multiply with 100. It is about 7cM

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Also you can understand second and third questions' answer more easily. If phenotypes are how plentiful, the distances are much farther

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The answers are
1) Smooth abdomen-straw body-lobe or lobe-straw body-smooth abdomen. Both of them same
2)Lobe
3)Smooth abdomen

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If you have more questions about this subject or anothers, ask me without hesitation