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Chapter 13

BIO 311C Chapter Notes - Chapter 13: Sister Chromatids, Germ Cell, Cell Division

Course Code
BIO 311C
A Latham

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`Cell Cycle
Introduction: The ability of organisms to produce more of their own kind best
distinguishes living things from nonliving matter
The continuity of life is based on the reproduction of cells, or cell division
Cell division is an integral part of the cell cycle, the life of a a cell from formation
to its own division.
Concept 12.1:
Cellular Organization of the Genetic Material
Most cell division results in daughter cells with identical genetic
information, DNA
The Exception is meiosis, a special type of division that can produce sperm
and egg cells
DNA molecules in a cell are packaged into chromosomes
Eukaryotic chromosomes consist of chromatin, a complex of DNA and
protein that condenses during cell division
Every eukaryotic species has a characteristic of number of chromosomes in
each cell nucleus
Somatic cells (non-reproductive cells) have two sets of chromosomes.
Diploid in nature (2n)
Germ cells (reproductive cells: sperm and eggs) have half as many
chromosomes as somatic cells. Produce haploid gametes (n)
Distribution of Chromosomes During Eukaryotic Cell Division
In preparation for cell division, DNA is replicated and the chromosomes
Each duplicated chromosomes has two sister chromatids (joined copies
of the original chromosome), which separate during cell division.
The centromere is the arro aist of the dupliated hroosoe,
where the two chromatids are most closely attached (Show slide)
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During cell division, the two sister chromatids of each duplicated
chromosome separate and move into two nuclei
Once separate, the chromatids are called chromosomes (1 tail= 1
Eukaryotic cell division consists of
a. Mitosis, the division of the genetic material in the nucleus
b. Cytokinesis, the division of the cytoplasm
Gametes are produced by a variation of cell division called meiosis
Meiosis yields non-identical daughter cells that have only one set of
chromosomes, half as many as the parent cell
Phases of the Cell Cycle
The cell cycle consists of
-Mitotic (M) phase (mitosis and cytokinesis)
-Interphase (cell growth and copying of chromosomes in preparation for
cell division)
Mitosis is conventionally divided into five phases
-Prophase: Chromatin condenses making the chromosomes visible
-Prometaphase: Nuclear envelope breaks down
-Metaphase: The Chromosomes become aligned at the equatorial plane
-Anaphase: Sister chromatids separate and the resultant daughter
chromosomes move toward the poles
-Telophase: Daughter chromosomes reach the poles and form the two new
Show slide
The Mitotic Spindle
The mitotic spindle is a structure made of microtubules that controls
chromosome movement during mitosis
In animal cells, assembly of spindle microtubules begins in the centrosome,
the microtubule organizing center
The centrosome replicated during interphase, forming two centrosomes
that migrate to opposite ends of the cell during prophase and
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