CELL REPRODUCTION · 2019-01-14 · CELL REPRODUCTION •Cell Division: process by which a cell...
Transcript of CELL REPRODUCTION · 2019-01-14 · CELL REPRODUCTION •Cell Division: process by which a cell...
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CELL REPRODUCTION
THE CELL CYCLE
AND
MITOSIS
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Lesson Objectives—Cell Cycle
• Describe the properties of cell division in prokaryotes.
• Describe cell division in eukaryotes. Explain the main
differences between cell division in prokaryotic and
eukaryotic cells.
• Describe the basic properties of chromosomes.
• Describe the key steps in the cell cycle.
• Identify and describe the main processes in mitosis.
• Describe how the cell cycle is controlled and define
cancer.
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Vocabulary
• Genes are the basic unit of heredity.
• Chromosomes are composed of deoxyribonucleic acid
(DNA) and protein and are present in the nuclei of all
cells.
• Diploid- All humans have 46 chromosomes in the body
cells, which is the diploid (duplicate) number.
• Haploid-Half of the diploid number of chromosomes is
found in the gametes. 23 chromosomes.
• Homologous-Homo means same. Homologous refers
to the same or similar pairs of chromosomes.
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CELL REPRODUCTION
• Cell Division: process by which a cell divides to form
two new cells (daughter cells)
• Three types of cell division, or cell reproduction
– Prokaryotes (bacteria)
• Binary fission divides forming two new identical cells
– Eukaryotes
• Mitosis
– Cell or organism growth
– Replacement or repair of damaged cells
• Meiosis
– formation of sex cells, or gametes
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Why do cells divide?
1: DNA Overload
– If cells grow without limit, an “information crisis”
would develop
– DNA cannot serve the needs of the increasing size of
cell
2: Exchange of materials
– Food and oxygen have to cross membrane very
quickly
– Waste must get out
– If cell is too large, this occurs too slowly and cell will
die
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PROKARYOTIC CELL DIVISION • Binary fission
– 3 main steps:
1: DNA Replication—DNA is copied, resulting in 2
identical chromosomes
2: Chromosome Segregation—2 chromosomes separate,
move towards ends (poles) of cell
3: Cytokinesis—cytoplasm divides, forming 2 cells
– Each new daughter cell is
genetically identical to parent cell
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M phase
G2 phase
S phase
G1 phase
THE CELL CYCLE
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CELL CYCLE-INTERPHASE
• Interphase: period of growth and DNA replication between cell divisions
• Three phases:
– G1 Phase
• cell increases in size
– S Phase
• Replication of chromosomes
– Now two strands called sister chromatids joined by a centromere
– G2 Phase
• organelles double
• new cytoplasm forms
• All other structures needed for mitosis form
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EUKARYOTIC CELL DIVISION
• DNA found on chromosomes located in nucleus of cell
• Cell cycle continuous process
– Cells grow
– DNA replicated
– Organelles duplicated
– Divide to form daughter cells
– 2 Main steps:
1: Mitosis (4 steps—Prophase, Metaphase, Anaphase, Telophase)
Nucleus divides
2: Cytokinesis—Cytoplasm divide, forming 2 cells
Each new daughter cell is genetically identical to parent cell
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• Mitosis = nuclear division
• Mitosis is followed by cytokinesis (cell division) • The steps of mitosis ensure that each new cell
has the exact same number of chromosomes as the original
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MITOSIS
• Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes. Mitosis is the cell division which occurs in all body cells except in gamete formation.
• Continuous process
• Four phases (PMAT)
– Prophase
– Metaphase
– Anaphase
– Telophase
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MITOSIS
• Mitosis results in the formation of two genetically identical cells each containing the same number of chromosomes as the parent cell, the diploid or 2n number.
• Mitosis ensures that the species number of chromosomes is maintained.
• Mitosis ensures that each daughter cell receives an identical combination of genes.
• Mitosis is the method by which all cells of a multicellular organism are formed from the zygote, thus it is essential for growth.
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• (1)Prophase • (2)Metaphase • (3)Anaphase • (4)Telophase
•PMAT
Interphase 1 2
3 4
Cytokinesis
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1. chromosomes visible (sister chromatids) 2. centrioles migrate to the poles (only in animals) 3. nuclear membrane disappears
4. spindle forms
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1. chromosomes line up on the equator of the cell 2. spindles attach to centromeres
Equator
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1. sister chromatids separate 2. centromeres divide 3. sister chromatids move to opposite poles
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1. chromosomes uncoil • now chromatin
2. nuclear membranes reform
3. spindle disappears
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-Occurs at end of Mitosis --division of the cytoplasm to form 2 new daughter
cells
--organelles are divided
-Daughter cells are genetically identical
Cells return to interphase
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1.Name the phases starting at the top.
Mitosis
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2.Name the phase
3.Identify X
4.Identify Y
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5. Name the phase
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6. Name the phase
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Control of the Cell Cycle
• Regulatory proteins called cyclins control the cell
cycle at checkpoints:
• G1 Checkpoint—decides whether or not cell will
divide
• S Checkpoint—determines if DNA has been
properly replicated
• Mitotic Spindle Checkpoint—ensures
chromosomes are aligned at mitotic plate
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Cell Cycle Checkpoints
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CANCER CELLS
• Result of uncontrolled cell division of cells that
have lost ability to regulate cell cycle
• Reproduce more rapidly than normal cells
• Masses formed called ‘tumors’
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Lesson Summary—Cell Cycle • The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell.
• Binary fission is a form of cell division in prokaryotic organisms that produces identical
offspring.
• As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a
structure, known as a chromosome.
• The DNA copies during the S phase of the cell cycle, resulting in a chromosome that
consists of two identical chromatids, known as sister chromatids, attached at a region
called the centromere.
• Any cell containing two sets of chromosomes is said to be diploid; the zygote forms
from the fusion of two haploid gametes.
• The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase,
the second growth (G2) phase, mitosis, and cytokinesis.
• Mitosis is the division of the nucleus; four distinct phases of mitosis have been
recognized: prophase, metaphase, anaphase, and telophase.
• Cytokinesis is the division of the cytoplasm.
• The cell cycle is controlled through feedback mechanisms.
• Cancer results from uncontrolled cell division, due to the loss of regulation of the cell
cycle.