Cell division occurs through mitosis and meiosis. Mitosis produces two identical daughter cells from a single parent cell during growth and repair. Meiosis produces gametes with half the number of chromosomes for sexual reproduction. During meiosis, one round of chromosome duplication and two rounds of cell division result in four haploid cells each with a unique combination of chromosomes from the original parent cell. This genetic variation among gametes allows for genetic diversity in offspring that is important for species evolution and survival.

1. The cell cycle, mitosis, and
meiosis
I. Cell Division and the Cell Cycle

2. I. Cell Division and the Cell Cycle
A. Why do cells divide?
1. large cells have difficulty transporting enough
nutrients across their membrane
2. Cells are limited in size by their SURFACE AREA
and VOLUME ratio

3. I. Cell Division and the Cell Cycle
B. Cell division
1. the process in which one cell, called the parent
cell, divides to form two new cells, referred to as
daughter cells

4. I. Cell Division and the Cell Cycle
2. Cell cycle and division in prokaryotes
a. prokaryotic cells divide by binary fission
b. Happens in three steps
i. DNA replication happens just before the cell divides, its
DNA is copied
ii. chromosome segregation, the two chromosomes
segregate, or separate, and move to opposite ends of the
cell
iii. Separation a new plasma membrane starts growing into the
center of the cell, and the cytoplasm splits apart, forming
two daughter cells

5. I. Cell Division and the Cell Cycle

6. I. Cell Division and the Cell Cycle
3. Cell cycle and division in eukaryotes
a. It occurs it two main phases mitosis and interphase
b. Interphase lead up to mitosis and has three major
phases
i. Growth Phase 1 (G1): during this phase, the cell grows
rapidly, while performing routine metabolic processes
ii. Synthesis Phase (S): during this phase, the cell’s DNA is
copied in the process of DNA replication
iii. Growth Phase 2 (G2): during this phase, the cell makes final
preparations to divide

7. I. Cell Division and the Cell Cycle

8. I. Cell Division and the Cell Cycle
c. Control of the cell cycle
i. The cell cycle is controlled by regulatory proteins at three
key checkpoints in the cycle
ii. The proteins signal the cell to either start or delay the next
phase of the cycle

9. I. Cell Division and the Cell Cycle

10. I. Cell Division and the Cell Cycle
C. Cancer
1. is a disease that occurs when the cell cycle is no
longer regulated
2. Cancer cells grow rapidly and may form a mass of
abnormal cells called a tumor
a. The cells take up nutrients and space that normal cells
need, this can damage tissues and organs and
eventually lead to death

11. I. Cell Division and the Cell Cycle

12. The cell cycle, mitosis, and
meiosis
II. Chromosomes and Mitosis

13. II. Chromosomes and Mitosis
A. Chromosomes
1. Chromosomes are the form of the genetic
material of a cell during cell division only the rest
of the time DNA is known as chromatin
2. Chromosomes contain
genes, which code for
proteins

14. II. Chromosomes and Mitosis
3. they are too dense to do any work only purpose
to ensure all DNA is transferred to daughter cells

15. II. Chromosomes and Mitosis
3. Human Chromosomes
a. Human cells normally have two sets of chromosomes,
one set inherited from each parent
b. 23 chromosomes in each set, for a total of 46
chromosomes per cell
c. Each pair are known as homologous chromosomes

16. II. Chromosomes and Mitosis
B. Mitosis
1. Prophase
a. chromatin condenses into chromosomes
b. the nuclear envelope breaks down

17. II. Chromosomes and Mitosis
2. metaphase
a. spindle fibers attach to the centromere of each pair
of sister chromatids
b. the sister chromatids line
up at the center of the cell

18. II. Chromosomes and Mitosis
3. anaphase
a. sister chromatids separate and the centromeres divide

19. II. Chromosomes and Mitosis
4. telophase
a. the chromosomes begin to uncoil and form chromatin
b. The spindle also breaks down
c. new nuclear membranes form

20. II. Chromosomes and Mitosis
C. Cytokinesis
1. the cytoplasm splits in two and the cell divides

21. The cell cycle mitosis and meiosis
III. Reproduction and Meiosis

22. III. Reproduction and Meiosis
A. Reproduction
1. is the process by which organisms give rise to
offspring
a. It is one of the defining characteristics of living things

23. III. Reproduction and Meiosis
2. Asexual reproduction
a. involves a single parent
b. It results in offspring that are genetically identical to
each other and to the parent
c. All prokaryotes and some eukaryotes reproduce this
way
d. Asexual reproduction can be very rapid

24. III. Reproduction and Meiosis
e. Happens 3 ways
i. Binary fission occurs when a parent cell splits
into two identical daughter cells of the same size

25. III. Reproduction and Meiosis
ii. Fragmentation occurs when a parent organism breaks into
fragments, or pieces, and each fragment develops into a
new organism

26. III. Reproduction and Meiosis
iii. Budding occurs when a parent cell forms a bubble-like bud.
The bud stays attached to the parent cell while it grows and
develops

27. III. Reproduction and Meiosis
3. Sexual reproduction
a. involves two parents
b. parents produce reproductive cells—called gametes
which are haploid cells
c. The process in which two gametes unite is called
fertilization
d. The fertilized cell that results is referred to as a zygote
which are diploid cells

28. III. Reproduction and Meiosis
e. Meiosis
i. Meiosis I
a. Prophase I
1. The nuclear envelope begins to break
down, and the chromosomes condense
2. homologous chromosomes pair up,
which is unique to prophase I

29. III. Reproduction and Meiosis
b. Metaphase I
1. Spindle fibers attach to the paired homologous
chromosomes
2. The paired chromosomes line up along the
equator of the cell,
this occurs only in metaphase I

30. III. Reproduction and Meiosis
c. Anaphase I:
1. the chromosomes of each homologous pair
start to separate from each other
2. the chromosomes moves toward the
opposite poles.

31. III. Reproduction and Meiosis
d. Telophase I and Cytokinesis
1. The spindle breaks down, and new nuclear
membranes form
2. the cytoplasm of the cell divides, and two
haploid daughter cells result
3. The daughter cells each have a random
assortment of chromosomes, with one from
each homologous pair, both daughter cells go
on to meiosis II

32. III. Reproduction and Meiosis
ii. Meiosis II
a. Prophase II
i. The nuclear envelope breaks down and the
spindle begins to form in each haploid
daughter cell

33. III. Reproduction and Meiosis
b. Metaphase II
i. Spindle fibers line up the sister
chromatids of each chromosome
along the equator of the cell

34. III. Reproduction and Meiosis
c. Anaphase II
i. Sister chromatids separate and move to
opposite poles

35. III. Reproduction and Meiosis
d. Telophase II and Cytokinesis
i. The spindle breaks down, and new nuclear
membranes form
ii. The cytoplasm of each cell divides, and four
haploid cells result.
iii. Each cell has a unique combination of
chromosomes.

36. III. Reproduction and Meiosis
f. Gametogenesis
i. The development of haploid cells (from meiosis) into
gametes
ii. This is another step the cells must take to be ready
for fertilization
iii. in humans the male gametes are sperm and female
are eggs

37. III. Reproduction and Meiosis
g. Sexual Reproduction and Genetic Variation
happens in three ways
i. Crossing over- the exchange of genetic material
between non-sister chromatids of homologous
chromosomes
ii. Independent assortment- homologous chromosomes
are randomly distributed to daughter cells
iii. Two gametes- with different genes from each of the
parents involved

38. III. Reproduction and Meiosis
h. life cycle
i. is the sequence of stages an organisms goes through
from one generation to the next.
ii. Haploid, diploid, and alternation of generations.