The document discusses cellular reproduction and genetics. It describes the cell cycle, which consists of interphase and cell division. Interphase includes three stages: G1 for cell growth, S for DNA replication, and G2 for more cell growth. During interphase, the chromosome doubles in preparation for cell division. The number and structure of chromosomes are characteristic of different species and help determine inherited traits.

1. Unit 4
MODULE
5
CELLULAR
REPRODUCTION
AND GENETICS
The Chromosome
The Cell Cycle

2. Learning Competency:
(S8LT-Ivd-16)
Compare mitosis and meiosis,
and their role in the cell-
division cycle

3. When you look at your
parents, you can see features
that you share with them, such
as the shape of the eye, the
presence of dimples, or even
the hand you use when you
write. The sharing of features
can be explained by heredity,
where traits are passed on from
parents to offspring.
3
Overview

4. Yet when you look at
your brothers and sisters,
even if you share the same
parents, each one of you
can be considered unique
based on the combination
of traits each possesses.
That is variation, which
demonstrates differences
among individuals.
4
Overview

5. 5
What is Genetics?
Genetics is the study of
heredity and variation.
It aims to understand how
traits can be passed on to
the next generation and
how variation arises.

6. 6
The Chromosome
All living things contain what
we call the genetic material that
serves as the set of instructions
that direct the activities and
functions of the cells. These
genetic materials, also known as
the deoxyribonucleic acid or DNA,
are passed on from one gene-
ration to the next to ensure the
continuity of life.

7. 7
The Chromosome
In eukaryotic cells (cells with
organelles), the DNA are bound with
proteins and are organized as beads
on strings to form chromosomes.
Chromosome is a rod-shaped
structure , usually found in pairs in a
cell nucleus, that carries the genes
that determine sex and the charac-
teristics an organism inherits from
its parents.

8. 8
The Chromosome

9. 9
The Chromosome
The num-
ber of chromo-
somes in a cell is
characteristic of
the species to
which it be-
longs. For exam-
ple, humans
have 46 chro-
mosomes while
rice have 12.

10. 10
The Parts of the Chromosome

11. 11
Table 1. Chromosome Numbers
of Selected Organisms
Organism Chromosome
No.
Saccharomyces cerevisiae
(common yeast)
32
Caenorhabdites elegans
(roundworm)
12
Drosophila melanogaster
(fruit fly)
8
Canis lupus familiaris
(dog)
52

12. 12
Table 1. Chromosome Numbers
of Selected Organisms
Organism
Chromosome
No.
Homo sapiens
(man)
46
Arabidopsis thaliana
(mouse ear cress)
10
Oryza sativa
(rice)
24
Zea mays
(corn)
20

13. 13
The chromosomes of a cell
change form as the cell transitions
from one stage to another in a
typical cell cycle.
The cell cycle is an orderly
sequence of events from the time a
eukaryotic cell divides to form two
daughter cells to the time those
daughter cells divide again.

14. 14

15. 15
The Two Stages of the Cell Cycle
1. Interphase
- where the chromosomes are long and
extended and are also referred to as
chromatin.
2. Cell division phase
- where the chromosomes
become condensed or
thickened.

16. 16
The Interphase
- refers to the period that follows one
cell division and precedes another.
- during this stage, the cell does not
divide; it merely grows.
- the chromosome doubles or
replicates itself because the
DNA molecule contained in
the chromosome produces
an exact copy of itself.

17. 17
The Interphase

18. 18
The Three Substages of Interphase
1. First Gap Period – or G1
- refers to the stage from the formation of
a new cell until it begins to replicate its
DNA.
- during this stage, the cell grows
initially.
- this stage is characterized by
protein and ribonucleic acid
(RNA) synthesis.

19. 19
The Three Substages of Interphase
1. First Gap Period – or G1
- RNA, which is synthesized based on the
DNA, is then used to synthesize proteins.
2. Synthesis Stage – or S
- the middle stage of interphase.
- the chromosomes are duplica-
ted in preparation for the next
cell division.

20. 20
The Three Substages of Interphase
3. Second Gap Period – or G1
- falls between the S period and the next
cell division or M (mitosis or meiosis)
phase.
- represents a period of rapid cell
growth to prepare for cell divis-
ion.

21. 21
Summary: