What must happen before meiosis can begin?
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a. dna must duplicate four times.
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b. the chromosomes must replicate.
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c. four haploid cells are produced.
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d. the cell splits into four parts.

Hello! Your answer is B, the chromosomes must replicate.

Meiosis is a process which takes one diploid cell (46 chromosomes) and makes 4 haploid cells (23 chromosomes). In order to do this, the DNA must divide. This is because it takes 46 chromosomes, to make 4*23 chromosomes, or 92.

We see here that the amount of chromosomes must double before meiosis. This therefore means A is incorrect, as the DNA only needs to duplicate 2 times. This also proves B correct, as the replication of chromosomes is what we're looking for.

C and D are incorrect, as they are actual processes in meiosis, meaning they do not happen before.

Hope this helps!

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.