Meiosis - Cell Division

Question 1

How meiosis takes place

Answer 1

meiosis is the cell division of one cell into four cells each of which only has half the chromosome number as the parent cell and each of the four cells is genetically different from each other and the parent cell
In meiosis, the nucleus undergoes two divisions viz, the first division (meiosis 1) and the second division (meiosis 2). The cell cycle that DNA replication takes place before meiosis begins during a stage called Interphase.

Question 2

Interphase

Answer 2

In preparation for the first nuclear division, DNA replicates so that the genetic material is doubled in the chromatin network
Single stranded chromosomes become double stranded

Question 3

Prophase 1

Answer 3

Nuclear Membrane begins to disappear
Chromatin Network unwinds to form distinct chromosomes
Each chromosome is made up of two identical chromatids (because of DNA replication in Interphase)
The chromosomes come together in homologous pairs i.e. two identical chromosomes, one of maternal origin and one of paternal origin
Crossing-Over takes place between chromatids of homologous chromosomes leading to the exchange of genetic material
Centrosome splits into two centrioles which start moving to opposite poles

Question 4

Metaphase 1

Answer 4

Spindle threads form between the centrioles
The chromosomes become arranged along the equator in Homologous Pairs, attached to spindle threads

Question 5

Anaphase 1

Answer 5

Spindle threads contracts
The two chromosomes of each homologous pair (each with two chromatids) are pulled to opposite poles

Question 6

Telophase 1

Answer 6

Two groups of chromosomes appear forming a nucleus at each pole
The cytoplasm divides to form two new cells
Thus we have a nucleus in each cell within which there is half the number of chromosomes as the original
The two new cell (A and B) are also genetically different because of crossing over