Cellular Reproduction (Mitosis and Meiosis)

1. CELLie’s Life
...a journey worth knowing

2. Heredity and Variation

3. Heredity and Variation

4. Heredity and Variation

5. 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. Heredity and Variation
Heredity - traits are passed on from parents to offspring.
Variation – demonstrates differences among individuals.
Example: physical similarities and differences
(eyes, nose skin, height)
abnormalities (color blindness, insanity, down
syndrome, diabetes, cancer)

7. Cellular Reproduction
 cells reproduce by dividing into two in the process called
cell division
 each dividing cell is called mother cell or parent cell,
and its descendants are called daughter cells
 the parent cell transmits copies of its hereditary
information (DNA) to its daughter cells which in turn,
pass it to their own daughter cells, becoming yet another
parent cell, and so on and so forth

8.  cell division is often referred to as cellular reproduction
 most prokaryotic cells, by simply separating the contents
of the cell into two parts
 eukaryotic cells can divide either through a process
called mitosis or meiosis.
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9. CELL CYCLE
 takes 24 hours for a mammalian cell to complete
 involves the following events:
Periodic replication of DNA
Segregation of this replicated DNA with cellular
constituents to daughter cells
 two general phases:
Interphase
Mitotic phase

10. Figure 1. Events in cell cycle
Mphase

11. INTERPHASE
-consists of G1 phase, S phase, and G2 phase.
G1 PHASE
Gap1 phase
growth and increase in cell mass
preparation for DNA replication
lasts for about 10 hours complete

12. S phase
synthesis phase
DNA replication
protein synthesis
lasts for about nine hours to
hours to complete

13. DNA REPLICATION
process of copying genetic material
results to two identical copies of DNA
transmits genetic information from cell to cell during
reproduction
Precise base-pairing during DNA replication:
Adenine (A) – Guanine(G)
Cytosine (C) – Thymine (T)

14. PROTEIN SYNTHESIS
 Process whereby DNA encodes for the production of
amino acids and proteins
can be divided into two parts:
Transcription
making a copy of part of the information in DNA,
thus forming the messenger RNA (mRNA)
Translation
converting that copied information, the mRNA, into a
protein with the aid of transfer RNA (tRNA)

15. G2 PHASE
Gap2 phase
post DNA replication phase
shortest of the three phases of
interphase
preparation for mitotic
cell division
lasts for about four hours
to complete
Figure1

16. MITOTIC PHASE
signals the actual division of the cell
lasts for about one hour to complete
the two sister chromatids separate from each other,
one going to each of the two daughter cells
results to two daughter cells identical to each other
and to the parent cell
Figure1

17. Two Types of Cell Division
Mitosis
Meiosis

18. Mitosis
 comes from the Greek word mitos meaning “thread”
 occurs in somatic or body cells
 consists of four stages:
Prophase
Metaphase
Anaphase
Telophase

19. PROPHASE
 phase of preparation
 chromatin condense into chromosomes
 nuclear membrane starts to breakdown
 nucleoli become fragmented
and disperse in the cytoplasm
 centrosomes move to opposite
poles and microtubules begin to form

20. METAPHASE
 shortest phase
 nuclear membrane
completely disappears
 chromosomes assume
positions in the cell’s center
or equatorial plate

21. ANAPHASE
 migration phase
 centromeres separate
 sister chromatids of each
chromosomes disengage and
move toward opposite poles of the cell
 each chromatid at the opposite
poles has its own centromere and is now
considered to be a single chromosome

22. TELOPHASE
 phase of reconstruction
 chromosome movement is completed
 microtubules disassemble
 nuclear membrane is reconstructed
around each daughter nucleus
 nucleoli begin to reappear
 chromosomes uncoil and
become more extended
Figure2

23. CYTOKINESIS
 division of the cytoplasm
 the surface around the equatorial
region of the cell pushes in toward
the center and pinches the cell
into two parts
 two daughter cells are formed
Division

24. Figure 2. Mitosis in animal cell

25. Meiosis
 occurs only on reproductive cells or gametes
 chromosomal material replicates once and cell divides
twice
 produce four daughter nuclei, each containing a
haploid (n) number of chromosomes
 has two successive divisions
reductive division or the Meiosis I
 equational division or the Meiosis II

26. Meiosis I
 also known as reduction division
 here the number of chromosome is reduced by one-half
 homologous chromosomes pair, then segregate and
move to different nuclei

27.  consists of four stages:
Prophase I
Metaphase I
Anaphase I
Telophase I

28.  Prophase I – chromosomes are duplicated and each
consists of chromatids as in the process of mitosis
– but in here, homologous chromosomes
pair with each other forming a tetrad of chromatids
– such pairing is called synapsis and does
not occur in mitosis
 Metaphase I – the pairs of homologous chromosomes
line up across the spindle

29.  Anaphase I – the homologous chromosomes separate
from each other and move to the opposite poles of the
cell
 Telophase I – nuclear membrane forms around each
group of chromosomes forming two genetically not
identical daughter cells
– the separation of homologous
chromosomes results in the segregation of genes that
are on those chromosomes

30. Meiosis II
 also known as equational division
 the centromere splits and the sister chromatids separate
into different nuclei
 resembles a normal mitosis
Prophase II
Metaphase II
Anaphase II
Telophase II

31. Differences Between Mitosis and
Meiosis
MITOSIS
 occurs in somatic or body
cells
 direct cellular division
 produce two diploid
daughter cells
 the daughter cells are
exactly alike
MEIOSIS
 occurs in reproductive
cells or gametes
 has two successive
division (meiosis I and
meiosis II)
 produce four haploid
daughter cells
 the daughter cells are not
all alike

32. LIFE
You don’t get to choose howyour going to die or when. You can
only decide how you’re going to live.
- Joan Buez
See into life, don’t just look at it.
- Baxter
The best use of lifeis to spend it for something that outlastslife.
- WilliamJames