Using the illustration above, why are the chromosomes in two of the sex cells different from the chromosomes in the parent cell? A

the chromosomes from another parent cell were introduced

B

crossing over occurred in the chromosome

C

an insertion mutation occurred during replication

D

some of the genes were damaged during replication

A  the chromosomes from another parent cell were introduced

Explanation: A child is created when the male sex cell joins the female cell. If the male and female sex cells had the standard number of chromosomes, as is found in body cells then the zygote (baby) would have double that number of chromosomes. The number of chromosomes would keep doubling every generation. To avoid this doubling the parent's body cells split by miosis which halves the number of chromosomes and so when the sex cells join the total number of chromosomes is the same as that found in the parent's body cells.

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