Download The Process of Cell Division (10.2)

The Process of
Cell Division (10.2)
Chromosomes
Chromosomes: packages of DNA, or genetic information
Before dividing, the cell needs to prepare and copy its DNA
Prokaryotic Chromosomes
- DNA is found in the cytoplasm due to no nucleus
- Most contain a single, circular DNA chromosome that contains all the genetic
information
Chromosomes Cont.
Eukaryotic Chromosomes
- Eukaryotes have more genetic information compared to prokaryotes → more
chromosomes
-
Chromatin: unraveled for of DNA
-
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composed of chromosomes and histone protein
DNA + chromosomes = nucleosomes
- Chromosomes make it possible to separate DNA precisely during cell division
Eukaryotic Chromosomes
Cell Cycle
Cell Cycle: The cell grows, prepares for division, and divides to form two daughter cells
Prokaryotic Cell Cycle (Binary Fission)
- Once they grow to a certain size, the cell copies its DNA
- the 2 DNA chromosomes attach to different regions of the cell membrane
- a network of fibers forms between them stretching to the opposite side of the cell
- the fibers constrict and pinch inwards dividing the cytoplasm and chromosomes
Binary fission: the production of two genetically identical cells
Binary Fission
Cell Cycle
Eukaryotic Cell Cycle
-
Interphase: one division after another separated by an “in-between” variation of growth
1.
G1--Cell Growth: most cell growth happens now with increased cell size and protein production
2.
S--DNA Replication: new DNA is synthesized when chromosomes are replicated
3.
G2--Preparing for Cell Division: is the shortest phase when organelles need for replication are
produced
4.
M--Cell Division: quick cell division in the form of mitosis
5.
Mitosis: division of the nucleus
6.
Cytokinesis: division of the cytoplasm
Eukaryotic Cell Cycle
Mitosis
Mitosis: the division of the cell nucleus
Divided into 4 phases:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Prophase
Prophase: the genetic material inside the nucleus condenses and the duplicate chromosomes become
visible. Outside the nucleus, a spindle starts to form.
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Usually the longest (½ time)
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Centromere: the area where the duplicate DNA strands connect
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Chromatid: each DNA strand in the duplicate chromosome
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when mitosis is complete, the chromatids will separate between the two new daughter cells
Centrioles: parts made of microtubules that are built like a spindle and extend from the
centrosome
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Centrioles begin to move towards opposite poles and the nucleolus disappears towards the
end
Prophase
Metaphase
Metaphase: the centromeres of the duplicated
chromosomes line up across the center of the cell.
Spindle fibers connect the centromere of each
chromosome to the two poles of the spindle.
- Generally the shortest phase
Anaphase
Anaphase: the chromosomes (sister chromatids) separate and move along spindle
fibers to opposite ends of the cell
- sister chromatids are considered
individual chromosomes when
anaphase begins
- end: when the sister chromatids are
completely separated into two sides
Telophase
Telophase: the chromosome, which are distinct and condensed, begin to spread out
into a tangle of chromatin
- nuclear envelope reforms around each set of chromosomes
- spindle fibers begin to break apart
- nucleolus becomes visible
Cytokinesis
Cytokinesis: the division of cytoplasm; splitting one cell into two completely
separate cells (daughter cells)
Animal Cells → cell membrane draws inward creating a cleavage furrow until the
two cells pinch apart
Plant Cells → a cell plate forms halfway between the divided nuclei; the cell plate
develops into a cell membrane and separates the two cells; a cell wall forms between
the two membranes completing the process
Plant vs. Animal Cytokinesis