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and between genes A and C, 12%. Which gene is closest to gene A on the chromosome?

Multiple Choice

a. gene B
b. gene C
c. both are equidistant from gene A
d. cannot determine from the above data.

The other user is right. A and B are located the closest to each other. For each percent of crossing over, geneticists say the genes have a distance between them of one Map Unit. Since A and B only cross over 6% of the time, they are said to be 6 map units apart. Also, A and C are 12 map units apart.

One more thing, the genes don’t have to be arranged on the chromosome in the order ABC. They could also be arranged as CAB. We wouldn’t be able to determine the order of all three genes unless we were given the map distance between B and C.

I hope this helped.

2 Responses

1. avstne Says:
   February 15th, 2010 at 5:24 pm

   What’s best to do with these types of questions is to try and draw a little time line type thing, and use the percentages as units apart. So you know A and B are 6 apart, and A and C are 12 apart. If you think about it, if these three letters have to be in a straight line, it would make sense if they were in the order of A B C. This is becuase thereis 6 spots between A and B, while there is still 12 spots between A and C. So if you look at that little ‘time line’, you see that B is closest to A, so your answer is B Hope that makes sense!
   References :

2. The BURNiNATOR Says:
   February 15th, 2010 at 5:34 pm

   The other user is right. A and B are located the closest to each other. For each percent of crossing over, geneticists say the genes have a distance between them of one Map Unit. Since A and B only cross over 6% of the time, they are said to be 6 map units apart. Also, A and C are 12 map units apart.

   One more thing, the genes don’t have to be arranged on the chromosome in the order ABC. They could also be arranged as CAB. We wouldn’t be able to determine the order of all three genes unless we were given the map distance between B and C.

   I hope this helped.
   References :

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