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White raven [17]
3 years ago
9

A hybrid allotetraploid species (2n1 + 2n2 = 60) was backcrossed to one of the suspected parents (2n1 = 30). What is the ploidy

of the the F1 ?
15 chromosomes (n1)
30 chromosomes (2n1)
45 chromosomes (2n1 + n2)
60 chromosomes (2n)
90 chromosomes (2n1 + 2n2)
Biology
1 answer:
leonid [27]3 years ago
6 0

Answer:

45 chromosomes (2n1 + n2)

Explanation:

The allotetraploid 2n1+2n2=60 has 60 chromosomes total, two sets of them of type 1 and two sets of chromosomes from the other type (2).

If the suspected type 1 parent is diploid with 30 chromosomes, then the allotetraploid has 30 type 1 chromosomes and 30 type 2 chromosomes.

<u>During meiosis, the germ cells reduce the total chromosome number by half.</u>

  • The gametes produced by the allotetraploid will have 15 type 1 chromosomes and 15 type 2 chromosomes.
  • The gametes produced by the suspected parent will have 15 type 1 chromosomes.

When these gametes combine during the backcross, the F1 zygote will have a diploid number of 30 type 1 chromosomes (15 coming from the allotetraploid and 15 coming from the suspected parent) and 15 type 2 chromosomes (which will be haploid because they all came from the allotetraploid).

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Answer:

\mathbf{cummulative \ incidence = \dfrac{60}{1000}}

Explanation:

We recognize that total occurrence equals new cases of disease over time divided by the number of people at risk at the onset.

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\mathbf{cummulative \ incidence = \dfrac{New \ cases \ of \ disease \ occurrence}{Number  \ of \ population \ at \ risk \ at \ onset}}

Given that:

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∴

\mathbf{cummulative \ incidence = \dfrac{60}{1000}}

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