Topic 2.5 Cell division
description
Transcript of Topic 2.5 Cell division
2.5.1 Cell Cycle
2.5.2 Uncontrolled cell division: tumour cellsThe cell division cycle is regulated in a number of ways.
Certain agents can damage these regulatory elements.
When this happen, uncontrolled cell division can occur resulting in the formation of tumours.
2.5.2 Uncontrolled cell division: tumours cells
S OF INTERPHASE G2 OF INTERPHASE MITOTIC PHASE
2.5.3 Interphase
2.5.4 The phases of Mitosis: Prophase
MTOC (pair centrioles)
1. Chromosomes supercoil and become visible
2. The spindle of microtubules forms from the
MTOC (microtubule organizing centre)
1. In animal cell, the centrioles divide and
move to opposite ends (poles) of the
nucleus.
2. In plant cells, there are no centrioles and
the spindle microtubules forms
independently.
3. Each chromosome consists of two chromatids
held together by the centromere.
4. Nuclear envelop breaks down.
1. Spindle microtubules attaches to the
chromosomes by means of the centromere.
2. Chromosomes are moved to the equator of
the cell,
2.5.4 The phases of Mitosis: Metaphase
The pair of sister chromatids separate and the
spindle microtubules pull them towards opposite
poles of the cell.
2.5.4 The phases of Mitosis: Anaphase
1. The chromatids have now reached the poles
and can be regarded as distinct chromosomes.
2. The nuclear envelop forms around each group
of chromosomes.
3. Chromosomes uncoil
4. The cytoplasm divide by a process called
Cytokinesis.
2.5.4 The phases of Mitosis: Telophase
Cytokinesis: Cytoplasm division
2.5.5 Explain how mitosis produce two genetically identical nuclei
Reproduction. An ameba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism
Growth & Development. A sand dollar embryo shortly after the fertilized egg divided forming two cells.
Tissue renewal. This dividing bone marrow cells (arrow) will give rise to new blood cells.
2.5.6 Why do cells divide?1. Asexual Reproduction2. Growth & Embryonic Development3. Tissue Renewal