Transcript Review: Mitosis/Meiosis

Review: Mitosis/Meiosis
Q: Why do cells divide?
• Cell division is important for asexual reproduction,
which involves only one parent organism.
• Most growth in a multicellular organism happens
because cell division produces new cells.
• Cell division produces cells for repair.
• QUICK DNA REVIEW:
• The genetic material in cells is called
DNA.
• In eukaryotic cells, DNA is found in the
nucleus.
• A DNA molecule contains the
information that determines the traits
that a living thing inherits and needs to
live.
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Q: What is chromatin?
A: During most of a cell’s life cycle, DNA is found
in a mass of loose strands called chromatin.
• Before cell division, DNA is duplicated.
• As cell division begins, the chromatin are
compacted into visible structures called
chromosomes.
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Q: What are the three MAIN stages of
the cell cycle?
• The life cycle of a eukaryotic cell can
be divided into three stages:
interphase, mitosis, and cytokinesis.
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• Q: What happens in interphase?
• Interphase is the stage in the cell cycle
during which the cell is not dividing.
• The cell grows to about twice the size it was
when it was first produced. It produces
various organelles and engages in normal
life activities.
• DNA is replicated.
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• In prophase, the chromatin in the
nucleus condense into chromosomes.
The membrane around the nucleus
breaks down.
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• In metaphase, the chromosomes line
up in the middle of the cell.
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• In anaphase, each chromosome breaks up
into two chromatids. They are pulled to
opposite sides of the cell.
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• In telophase, a new nuclear membrane forms
around each group, and the chromosomes
unwind into chromatin.
• After telophase, cytokinesis begins.
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• After mitosis, cytokinesis results in two
new cells, and the two new cells start the
cell cycle again.
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•Q: What is the purpose of mitosis?
•A: To make identical body cells
•Q: In mitosis, if the cell starts with 10
chromosomes, how many chromosomes
should each cell have at the end of mitosis?
•A: 10 chromosomes each
Unit 6: Lesson 2 Meiosis
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How are sex cells made?
• Mitosis produces two new cells that contain exact
copies of the chromosomes of the parent cell.
• A different kind of cell division is needed to
produce sex cells.
• Meiosis is the type of cell division that produces
haploid sex cells such as sperm or egg cells.
• When an egg is fertilized by a sperm cell, a new
diploid cell forms.
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Why do organisms need sex cells?
• Normal human body cells contain 46
chromosomes.
• Sex cells are also known as gametes. Gametes
have only half of the usual number of
chromosomes.
• Gametes are haploid, meaning they have one
chromosome from each homologous pair.
Gametes are made in the reproductive organs.
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Why do organisms need sex cells?
• Sex cells are needed so that in sexual
reproduction offspring receive a total of
46 chromosomes.
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How does meiosis compare to
mitosis?
• Meiosis produces haploid cells.
Mitosis produces diploid cells.
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•Q: What is the purpose of meiosis?
•A: To make sex cells (eggs/sperm)
•Q: In Meiosis, if the cell starts with 10
chromosomes, how many should each
cell have at the end of meiosis?
•A: 5 chromosomes each