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

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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] · Answer 1 · 2022-05-24T08:39:32+03:00

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).