The document discusses the cell cycle, which involves three main stages - interphase, mitosis, and cytokinesis. Interphase consists of G1, S, and G2 phases where the cell grows and duplicates its DNA. Mitosis then follows, comprising prophase, metaphase, anaphase, and telophase where the cell nucleus and chromosomes divide. Finally, cytokinesis separates the cytoplasm into two daughter cells. The cell cycle is essential for growth, development, and repair of organisms as it leads to the production of new cells.

1. MEDICAL GENETICS
DMLS 107
TOPIC OF DISCUSSION
THE CELL CYCLE

2. OBJECTIVES
Students should be able to;
 Define cell cycle
 Identify the three stages involved in
the cell cycle
 Outline the need for the cell cycle

3. INTRODUCTION
 According to the cell theory, cells arise
from pre-existing cells.
 In order for living organisms to grow, there
is the need for cell division and this is
achieved through the cell cycle.
 The cell cycle is some how likened to the
seasons in the year.

4. contd.
 In some seasons, crops are produced whiles
in others there is no production. The cell
cycle also involves phases when the cell
grows and divides and phases when there is
no division.

5. What is the cell cycle?
The cell cycle refers to the different
stages in the life of a cell leading to the
formation of two identical daughter
cells. It involves the duplication of the
DNA [deoxyribonucleic acid] of a parent
cell.

6. Stages involved in the cell cycle
 Interphase[growth phase of
the cell]
 Mitotic phase[karyokinesis]
 Cytokinesis

7. INTERPHASE
 It is at this phase that growth and
metabolic activities take place. It
constitutes about 95% of the cell
cycle.
 It comprises of the; G₁,S and the G₂
phases.

8. contd

9. Gap 1[G₁]
Activities that occur;
 Synthesis of proteins and enzymes
 Formation of organelles
 Increase in the size of the cell
Chromosomes are not visible at this stage
NB:At the end of the G₁ phase, the cell decides
either to enter the synthesis phase or avoid cell
division by entering the G₀ phase.

10. Synthesis phase[S-PHASE]
At this phase there is replication of DNA.The
chromosome number doubles.
Before replication After replication

11. G₂[Gap 2]
 Microtubules are
formed at this
stage
 Energy is built up in
the cell in
preparation for
mitosis

12. Mitosis
 This phase of the cell cycle involves the
division of the nuclear material.
 Mitotic phase involves four stages leading
to the formation of two nuclei.
 The four stages involved in mitosis are;
-Prophase
-Metaphase
-Anaphase
-Telophase

13. CONTD
PROPHASE
 Chromosomes become visible and seen as
an x-shape under a microscope.
 Each chromosome contains one pair of
sister chromatids.
 Chromatids are joined together at a point
called the centromere
 The nuclear membrane disintegrates and
spindle fibers are formed.
 Microtubules grow out of the centrioles
and move towards opposite poles of the
cell.

14. contd.
METAPHASE
 Sister chromatids align
themselves at the equator of the
cell.
 Spindle fibres are fully formed
and microtubules are attached
to each sister chromatids.

15. contd.
ANAPHASE
 The anaphase begins when
sister chromatids begin to
split.
 The centromere divides and
the chromatids move to
opposite poles of the cell
along the spindle fibres.

16. contd.
TELOPHASE
 Spindle fibres disappear
 Chromosomes then uncoil and assume the
original thread-like forms.
 A nuclear membrane is formed around
each group of chromosomes

17. contd.
New nuclear membranes
Uncoiled chromosomes

18. contd.
CYTOKINESIS
 Involves the division of the cytoplasm into
two single compartment leading to the
formation of two daughter cells

19. contd.

20. contd.
THE NEED FOR CELL CYCLE
 It plays an important role in the
development of embryos and growth of
living organisms.
 Leads to the production of new cells and
the replacement and repair of old and
damaged cells.
 Leads to the increase in the number of
cells in living organisms

21. contd.

22. contd
WATCH A VIDEO

23. OVERVIEW
 All cells whether eukaryotic or prokaryotic
undergo division.
 The cell cycle involves three
phases;interphase,mitosis and cytokinesis.
 The interphase is the growth phase while
the mitosis phase involves the formation
of two nuclei
 The final phase, cytokinesis involves the
division of the cytoplasm.

24. GROUP MEMBERS
1. SENOO GIFTY DZIFA AKU
2. MARIAM YAKUBU
3. ERNEST TAABE
4. ENOCH KWAME OBUOBI
5. NIXON KWABENA NYANING
6. CALEB AMOAH
7. PHILIP QUAGRAINE