Chromosomes and Cell Reproduction

Objectives:1. Identify different types of cell division2. Differentiate between a gene, a DNA

molecule, a chromosome, and a chromatid.

3. Be able to compare haploid and diploid cells

4. Predict how mutations at the chromosome level can affect development.

About 2 trillions cells are produced by an adult human body every dayWhat are some of the reasons why cells need to divide in our bodies?

Why do cells reproduce

• For growth

• Repair

• And reproduction

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

There are 5 stages of Mitosis

plus CytokinesisInterphaseProphase

MetaphaseAnaphaseTelophase

and, Cytokinesis

Interphase

Cell grow and carries out if normal cell processes

DNA Replicates

Prophase• Nuclear membrane disintegrates

• Nucleolus (nuclear membrane) disappears

• Chromosomes condense

• Mitotic spindle begins to form between the poles

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 →

Metaphase

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

Anaphase

• Microtubules shorten, moving chromosomes to opposite poles

TelophaseTelophase

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

Cytokinesis

Plant CellsCell plate forms dividing daughter cells

Animal CellsCleavage furrow forms at equator of cell and pinches inward until cell divides in two

Cleavage → Furrow

The result is two identical daughter cellsThat are Diploid (having 2 copies of each chromosome).