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The cell cycle, mitosis, and meiosis
I. Cell Division and the Cell Cycle
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
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
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 stepsi. 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
I. Cell Division and the Cell Cycle
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 phasesi. 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
I. Cell Division and the Cell Cycle
I. Cell Division and the Cell Cycle
c. Control of the cell cyclei. 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
I. Cell Division and the Cell Cycle
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
I. Cell Division and the Cell Cycle
The cell cycle, mitosis, and meiosis
II. Chromosomes and Mitosis
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
II. Chromosomes and Mitosis
3. they are too dense to do any work only purpose to ensure all DNA is transferred to daughter cells
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
II. Chromosomes and Mitosis
B. Mitosis
1. Prophase
a. chromatin condenses into chromosomes
b. the nuclear envelope breaks down
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
II. Chromosomes and Mitosis
3. anaphase
a. sister chromatids separate and the centromeres divide
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
II. Chromosomes and Mitosis
C. Cytokinesis
1. the cytoplasm splits in two and the cell divides
The cell cycle mitosis and meiosis
III. Reproduction and Meiosis
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
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
III. Reproduction and Meiosis
e. Happens 3 waysi. Binary fission occurs when a parent cell splits
into two identical daughter cells of the same size
III. Reproduction and Meiosis
ii. Fragmentation occurs when a parent organism breaks into fragments, or pieces, and each fragment develops into a new organism
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
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
III. Reproduction and Meiosis
e. Meiosis
i. Meiosis Ia. 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
III. Reproduction and Meiosis
b. Metaphase I1. 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
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.
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
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
III. Reproduction and Meiosis
b. Metaphase II
i. Spindle fibers line up the sister
chromatids of each chromosome
along the equator of the cell
III. Reproduction and Meiosis
c. Anaphase II
i. Sister chromatids separate and move to
opposite poles
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.
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
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
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.