BRAINCAKELaw of Segregation
Mendel's first law is the law of segregation. It states that each characteristic is controlled by a pair of alleles, and that the two alleles separate (segregate) during gamete formation, so each gamete receives only one allele of each gene. At fertilisation, the pair is restored, one allele coming from each parent.
Mendel proposed this from his results before anyone knew about chromosomes or meiosis. We now know the physical explanation. The two alleles of a gene are at the same locus on a pair of homologous chromosomes. In anaphase I of meiosis the homologous chromosomes are pulled to opposite poles, so each gamete ends up with one chromosome of the pair and therefore one allele.
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Key terms in this lesson
- homologous chromosomes
- A pair of chromosomes, one from each parent, that carry the same genes at the same loci.
More in Genetic Information
- Monohybrid Crosses
- Test Cross
- Sampling Errors
- Mendel
- Law of Independent Assortment
- Multiple Alleles
- Codominance
- Dihybrid Crosses
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics