Types of Assortments / Recombination in Chromosomes

There are two types of Assortments of chromosomes that take place in Meiosis during the formation of gametes: Interchromosomic Assortment and Intrachromosomic Assortment.

The Interchromosomic Assortment :

This type of assortment takes place during the anaphase I of the reductional Meiosis.

Becker_JPEG_ch20_Builder

As you can see in the above document, there is an independent segregation of homologous chromosomes. Each chromosome was free to go in any daughter cell. The above document shows only one possibility, while another possibility can take place where the 2 red chromosomes go to one daughter cell while the 2 blue chromosomes go to the other daughter cell.

The Intrachromosomic Assortment:

In this type of assortment, the homologous chromosomes exchange segments of their sister chromatids. It takes place in prophase I of the reductional meiosis.

crossingover rec

After this exchange, the sister chromatids of the same chromosome may carry different alleles. After the completion of meiosis and when the gametes are formed,  we will have 2 types of gametes:

  • Parental gametes that will have the unchanged chromatids ( in this case, a gamete having AB and  another having ab).
  • Recombinant gametes which will have the recombinant , changed chromatids ( in this case, a gamete having Ab and another having aB).

Note that the probability of a crossing over to take place is usually low, so the percentages of the recombinant gametes will be much lower than those of the parental gametes.

Best Regards,

Yusser CHIDIAC Smile

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