MCD – Genetics 1 – Meiosis and Recombination
Anil Chopra
1. Explain the different stages of meiosis I
2. Draw a diagram of meiosis showing segregation of two pairs of chromosome
 The human karyotype consists do 22 pairs of autosomal chromosomes and one
pair of sex chromosomes.
 In mitosis, the cell divides so that each daughter cell is genetically identical to
its parent cell.
Interphase
Prophase Metaphase Anaphase Telophase
 In meiosis on the other hand, the daughter cells are all genetically different and
they are all haploid. They are gametes
Meiosis I
1) In interphase, DNA replication occurs.
2) In prophase I (of meiosis I), the chromosomes become visible and begin to
pair up into their homologous pairs.
3) In metaphase I the chromosomes line up randomly along the equator of the
cell in their homologous pairs and the spindle microtubules attach to the
centromeres. This is also where recombination takes place
4) In anaphase I, the chromosomes are pulled to opposite ends of the cell.
5) In telophase I the cell starts to split by cytokinesis. In each new
daughter cell, there is half the number of chromosomes but 2
chromatids in each one. This is the reduction division.
3. Explain what occurs at meiosis II
Meiosis II
This is essentially the same as mitosis, only that there is half
the number of chromosomes to split.
Therefore altogether the process of meiosis:
4. Explain how recombination of chromosomes occurs.
Recombination is the
crossing over of genetic
material between
chromosomes. This
means that genes, at
particular loci can
change place during
metaphase of meiosis I.
The recombination
fraction is the chance
that two different marked alleles on separate
chromosomes will be inherited together. This
increases as the two different alleles marked
are further away on the chromosomes.
Linkage is when the recombination fraction is more than 50% or 0.5.