Mitosis and Meiosis

Authors Avatar

Elmaz Korimbocus

Mitosis and Meiosis

MITOSIS

a)  Examples of where mitosis occurs in the body: - cell division is essential for growth, repair and reproduction, and replacing dead cells such as skin cells.

b)  The genetic information for a cell is stored in the nucleus, which contains coil-like structures known as chromosomes.  They contain the genetic information encoded in DNA, which enables the cell to carry out its functions.

c)  If a cell needs to make two exact copies of itself, its nucleus needs to divide in order to pass its information to the two daughter cells.  So there needs to be two sets of identical genetic information.

d)  A human cell has 23 pairs of chromosomes.

e)  Interphase:

  • Normal cell growth and metabolic function.
  • Synthesis of DNA.
  • Each chromosome homolog replicates, so that each homolog consists of two sister chromatids.
  • Normal growth and function.

Prophase:

  • Chromosomes coil and condense.
  • 2 sister chromatids attached at centromere.
  • Homologs not associated with one another.
  • Nucleolus disappears, nuclear membrane breaks down.
  • Centrioles (organelle important in mitosis, see below) duplicates, spindle fibers extend from centrioles.

Metaphase:

  • Nuclear membrane disappears, chromosomes maximally condensed.
  • Spindle fibers attach to centromeres.
  • Centromeres move to equatorial plane: metaphase plate.

Anaphase:

  • Centromeres separate.
  • Spindle fibre contracts.
  • Sister chromatids separate, move to opposite ends of cell: now called daughter chromosomes.

Telophase:

  • Chromosomes uncoil, become indistinct.
  • Nuclear membrane reappears, nucleoli reform, cell membrane (animals) or cell wall (plants) reforms.

1. a)  There are 23 chromosomes present in the two daughter cells at the end of mitosis.  At interphase, the chromosomes in the cell replicates, meaning that there will be 23 pairs of chromosomes in the one cell.  This is so that when the cell divides, both daughter cells will have a copy of the genetic information.                                          b)  If the numbers of chromosomes in the new cell did not make up 23, then there would be problems.  For example, it there are too many chromosomes then the body would naturally abort or would lead to a genetic disorder such as Down’s syndrome. c)  The two small cylinder-shaped bodies in the cell, the aster, are the radial array of microtubules of interphase cells with the centrosome at its centre.                                       d)  The genes on the chromosomes would be copied, and each daughter cell would have a copy.                                                                                                                           e)

Join now!

3. j)  Each daughter did get a copy of each gene on the chromosomes, if this did not happen then there would be genetic disorders occurring.                                              k)  Humans cannot be cloned easily because mitosis and meiosis are not simple processes. In fact, there are literally hundreds of genes that are needed to control the many steps that are involved and to be sure that those steps occur in the ...

This is a preview of the whole essay