Respuesta :

RonaldMcDonald6969

Answer:

2.2

Explanation:

Since all of the mice in the F1 generation are heterozygous for both traits, they contain a copy of each on separate chromosomes. (AB on one from parent 1 and ab on the other from the parent 2.)  If these chromosomes split away from each other without crossing over, the F2 offspring can ONLY by AABB or aabb.  This means that any heterozygous combinations are the result of crossing over and must be counted.  When all are counted, we get a total of 11, or 2.2 per cross.

marianaegarciaperedo

To calculate the mean number per cross of the offspring that result of crossing over, we need to make an addition of individuals that result from crossing-over, and divide the result by the number of crosses. The result is 2.2.

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According to the statement, crosses were as follow

Cross 1) Between two true-breeding

Parentals)  LLBB    x    llbb

F1) 100%  LlBb

Cross 2) Between two dihybrids

Parentals)  LlBb    x    LlBb

The results of the F2 are

Phenotype                      Cross1     Cross2     Cross3     Cross4     Cross5    

Long-Black                         6              5               5                 6            7

Long-White                         1               1                0                 2           2

Short-Black                         0             2                1                  1             1

Short-White                        2              3                 3                2            2          

If there is no crossing-over, offspring will have the same chromosomes as parentals, which are Long-Black (LB) or Short-White (lb), because these chromosomes separate without interchanging segments.

However, if there is crossing over, these chromosomes interchange segments, and the result is Long-White (Lb) and short-black (lB).

So now, we need to count how many individuals from the F2 are a result of crossing-over.

       Phenotype         Cross1   Cross2   Cross3   Cross4   Cross5     Total    

  • Long-White           1              1              0             2           2              6
  • Short-Black           0             2             1              1             1             5          

                                                                                                                  11

Eleven individuals result from crossing over. But we need to calculate the mean number per cross.

So, since there are 5 crosses, we need to divide the total number of individuals that are the result of crossing over by the total number of crosses.

  • total number of individuals = 11
  • total number of crosses = 5

Mean number per cross of F2 generation ⇒  11/5 = 2.2

The mean number per cross of F2 generation offspring that are the result of crossing over is 2.2

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You can learn more about crossing-over at

https://brainly.com/question/12911831?referrer=searchResults

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https://brainly.com/question/19671756?referrer=searchResults

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