Chromosomes and Cell Reproduction

1
Chromosomes and Cell Reproduction

• Objectives
• Identify different types of cell division
• Differentiate between a gene, a DNA molecule, a
  chromosome, and a chromatid.
• Be able to compare haploid and diploid cells
• Predict how mutations at the chromosome level can
  affect development.

2
About 2 trillions cells are produced by an adult
human body every day

• What are some of the reasons why cells need to
  divide in our bodies?

3
Why do cells reproduce

• For growth
• Repair
• And reproduction

4
There are Two Types of Cell Division

• Mitosis
• Makes new somatic cells (body cells)
• These cells are used for Growth and Repair of
  tissues

• Meiosis
• Makes germ cells or gametes ( egg and sperm)
• These cells are used for reproduction

5
There are 5 stages of Mitosisplus Cytokinesis

• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• and, Cytokinesis

6
Interphase

• Cell grow and carries out if normal cell
  processes
• DNA Replicates

7
Prophase

• Nuclear membrane disintegrates
• Nucleolus (nuclear membrane) disappears
• Chromosomes condense
• Mitotic spindle begins to form between the poles

8
Spindle ApparatusIncludes

• Centrioles Located at the poles of the cell, and
  send out spindle fibers.
• Spindle fibers attach to the centremere of each
  sister chromatid, in order to pull them apart.
• The spindle apparatus ensure that each new cell
  receives 1 full copy of the genetic material

?Centromere
?Spindle fiber
Centrioles ?
9
Metaphase

• Chromosomes attach to mitotic spindle and align
  along the metaphase plate (the equator of the
  cell).

10
Anaphase

• Microtubules shorten, moving chromosomes to
  opposite poles

11
Telophase

• Chromosomes reach poles of cell.
• Nuclear envelope re-forms.
• Nucleolus reappears.
• Chromosomes decondense.

12
Cytokinesis
Plant Cells Cell plate forms dividing daughter
cells
Animal Cells Cleavage furrow forms at equator of
cell and pinches inward until cell divides in two
Cleavage ? Furrow
13
The result is two identical daughter cellsThat
are Diploid (having 2 copies of each chromosome).