Human cell division

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Human Cell Division
-Mitosis
-Meiosis

1. RADIOBIOLOGY
Human Cell Division
Rahman Ud Din
Senior Lecturer Radiology
Northwest Institute of Health Sciences

2. LEARNING OUTCOMES
Cell Proliferation
Cell Cycle
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Meiosis
Tissues and Organs

3. CELL PROLIFERATION
An act of a cell to reproduce and multiply in number
Human body consists of;
Somatic cells
Genetic cells (oogonium and spermatogonium)
All body cells are somatic cells
Somatic cells proliferate by mitosis
Genetic cells undergo meiosis
Several rad (many grays) are needed for cell damage

4. CELL CYCLE
Geneticist see cell cycle as mitosis and interphase
Somatic cells division by stages (mitosis);
Prophase
Metaphase
Anaphase
Telophase
The portion of a cell cycle b/w mitotic events is called
interphase
Interphase is cell growth b/w division
In cell cycle; M, G1, S, G2 phases happens
Phases are characterised by structure of
chromosomes

5. CELL CYCLE …….
G1 is the pre-DNA synthesis phase
This is the gap in cell growth between M and S
S is the synthesis phase (DNA replicated in two identical
DNA daughter)
In S, chromosomes transferred from two chromatids
(centromere in centre) to four chromatids
Results in two pairs of homologous chromatids with
same DNA contents and structure
G2 phase is a post-DNA synthesis gap of a cell growth

6. MITOSIS
Chromosomes are not visible
DNA slowly takes the shape of chromosomes
Prophase
Nucleus swells, DNA prominent, structural form
Metaphase
Chromosomes appears, lined up equator of nucleus
Anaphase
Splitting of chromosomes at centromere, chromatids connected by fibers
Spindles fibers, chromosomes are half and moved towards the spindle
Telophase
Chromosomes into DNA, two nuclei (membrane covering), cytoplasm division

7. MEIOSIS
Genetic material changes by division process called meiosis
Genetic cells-somatic cells (23 pairs or 46 chromosomes)
If genetic cells marriage to another genetic cells (must be 23)
The union of genetic cells must result in 46
It starts with 46 chromosomes
Appears same at G2 phase and have completed
Progress into two daughter cells by mitosis
Contains 46 chromosomes of two chromatids each
All of sub phases are same

8. MEIOSIS
Each daughter cells progresses to second division
All material including chromosomes are divided
Second division not accompanied by S-phase
No replication of DNA occurs
No chromosomes are duplicated
The granddaughter cells contains only 23 chromosomes
Parent cell undergone two division
Some chromosomal material are exchanged by crossing over
Change in genetic constitution and changes in traits

9. TISSUES AND ORGANS
Collection of cells similar structure and function called tissues
Tissues are bound together to form organs
Different organs perform same function forms organ system
Tissues and organs of body includes stem cells and mature cells
They are susceptible to radiation based on degree of radiosensitivity
Assignment: Response to radiation in relation to cell type!?

10. THANK YOU