A human body cell has 46 chromosomes. How many chromosomes does a primary spermatocyte have? …
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A human body cell has chromosomes.
- How many chromosomes does a primary spermatocyte have?
- How many does one secondary spermatocyte have?
- How many chromosomes are there in all the four sperms made from one primary spermatocyte, taken together?
Need a reminder? The key ideaShow
A spermatogonium has chromosomes. A primary spermatocyte divides by meiosis I into two secondary spermatocytes ( chromosomes each). Each of these divides by meiosis II into two spermatids. Each spermatid becomes one sperm. A primary oocyte gives one ovum and up to three polar bodies. LH acts on the Leydig cells, and FSH acts on the Sertoli cells.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Body cell: chromosomes.
Plan. The number halves at meiosis I and stays the same at meiosis II.
Step 1. Primary spermatocyte. It is diploid, so .
Step 2. Secondary spermatocyte. Meiosis I halves the number, so .
Step 3. Four sperms. Each has , so in all.
Answer: ; ; .
Check. One primary spermatocyte has . The four sperms together have twice that number because meiosis I halves the cells and meiosis II makes four of them.
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