BRAINCAKEMeiosis
Meiosis is a type of cell division that produces four haploid daughter cells from one diploid parent cell, each genetically different. It is called a reduction division because the chromosome number is halved.
Diploid cells contain pairs of homologous chromosomes: one chromosome of each pair came from the mother and one from the father. Homologous chromosomes are the same size, have the centromere in the same position and carry the same genes at the same loci, although they may carry different alleles.
Before meiosis, DNA replicates during interphase, so each chromosome consists of two sister chromatids. There are then two divisions:
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Key terms in this lesson
- sister chromatids
- The two identical copies of a chromosome, joined at the centromere, produced when DNA replicates before cell division.
- crossing over
- The exchange of sections of DNA between non-sister chromatids of homologous chromosomes during meiosis, producing new combinations of alleles.
- independent assortment
- The random separation of homologous chromosome pairs into gametes during meiosis, producing different combinations of maternal and paternal chromosomes.
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All 28 lessons in Meiosis and Sexual Reproduction · All Edexcel AS-level Biology topics