Help! I don’t understand meiosis at all 😩
Hi everyone. I’m studying for my biology exam and meiosis is killing me. Can someone explain what happens in meiosis in very simple words? I know it makes sperm and eggs but the phases are so confusing. How many divisions? What is the main difference between meiosis I and II? Why do we need crossing over? Please help, I’m lost. Thanks!
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Hey, don’t worry, meiosis is actually pretty straightforward once you break it down. Meiosis is a special cell division that makes gametes (sperm and egg cells) with half the normal number of chromosomes. It has two big divisions: meiosis I and meiosis II.
Before anything starts, the DNA is copied, so each chromosome has two identical sister chromatids.
Meiosis I is the reduction division:
Prophase I → chromosomes condense, homologous chromosomes pair up and do crossing over (they swap pieces → creates genetic variety)
Metaphase I → homologous pairs line up in the middle
Anaphase I → homologous chromosomes (each still two chromatids) are pulled to opposite sides
Telophase I + cytokinesis → two haploid cells (each chromosome still has two chromatids)
Meiosis II is like mitosis:
Prophase II → chromosomes condense again
Metaphase II → chromosomes (now single ones with two chromatids) line up singly
Anaphase II → sister chromatids separate
Telophase II + cytokinesis → four haploid cells with one chromatid each
The most important thing is phases of meiosis — you can check a very clear explanation here.
It has nice pictures and simple steps.