AP Bio Ch. 12, Cell cycle
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Transcript of AP Bio Ch. 12, Cell cycle
![Page 1: AP Bio Ch. 12, Cell cycle](https://reader035.fdocuments.net/reader035/viewer/2022062319/555039b2b4c9058f2f8b5548/html5/thumbnails/1.jpg)
The Cell Cycle & Mitosis
Ch. 12
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Main goals for this lecture
1. Distinguish between chromosomes, chromatids, and chromatin
2. Correctly model and identify in pictures each stage of the cell cycle
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The Main Ideas
1. Cell division results in 2 genetically identical daughter cells
2. The mitotic phase alternates with interphase in the cell cycle
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The unity of life
• All living things reproduce
• Reproduction occurs at the cellular level
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The many functions of cell division
• REPRODUCTION: In unicellular organisms - leads to an increase in the size of the population
• In multicellular organisms - – GROWTH: a single fertilized egg (zygote) divides to
form a new organism– REPAIR: Repairs and renews old or damaged cells
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Cell Division results in identical daughter cells
• The DNA is copied and divided between the 2 new cells
• Each new cell (daughter) contains an exact copy of the original DNA
• In human cells, there is about 6 feet of DNA to copy and neatly and accurately divide between the 2 new cells!
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Quick Think
What is the purpose of mitosis?
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DNA• A cell’s genetic information
is called its genome– In bacteria (prokaryotic cells)
it is usually 1 long circular DNA molecule
– In plants, animals, and fungi (eukaryotic cells) is it usually several linear molecules of DNA
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Chromosomes• The individual molecules of DNA are
packaged into chromosomes• Each species has a characteristic number of
chromosomes– Humans - 46– Camel 70– Alligator - 32– Chicken - 78– King crab - 208– Corn - 20
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Quick Think
Is the complexity of the organisms directly
proportional to the number of chromosomes? Explain
your answer.
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Chromosomes• Chromosomes
are made of chromatin– DNA + proteins
• THE DNA PART: Each chromosome is a single long piece of DNA coding for 100s or 1000s of genes
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Chromosomes
• THE PROTEIN PART: the proteins help keep the shape of the chromosome and help control the activity of the genes
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Quick Think
• So…what’s a chromosome?
• What is it made of?
• What is it’s purpose?
• Where is it found?
• How many do we have?
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Chromosomes• When the cell is dividing the DNA is tightly
packed into X-shaped chromosomes• When the cell is not dividing, the DNA is more
loose - just chromatin strands
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Quick Think
• How does the appearance of chromatin and chromosomes vary?
• Draw them…?
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Getting the DNA ready for cell division
• Before a cell divides, the DNA (chromatin) condenses and folds into a neat, tightly packed chromosome
• Each chromosome is made up of 2 sister chromatids - identical copies of that particular chromosome
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Chromosomes
• The 2 sister chromatids are attached with sticky proteins
• The place where they are attached is called the centromere
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Quick Think
Distinguish between chromatin,
chromosomes, and chromatids?
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Chromosomes• During cell division, the 2 sister
chromatids are pulled apart to opposite ends of the cell and repackaged into new nuclei
• They are now considered individual chromosomes
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Mitosis
• The formation of 2 daughter nuclei
• Followed by the division of the cytoplasm and organelles called cytokinesis
Notice! Not 2 new cells. 2 new nuclei.
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Mitosis and Interphase
• Mitotic (M) phase - ~10% of a cell’s life
• Interphase - ~90% of a cell’s life
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Interphase• During this time
the cell:– grows– produces proteins
& organelles – copies its
chromosomes– Prepares for cell
division
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Interphase• 3 phases:
– G1 phase = first gap• Cell is making proteins and
organelles
– S phase = synthesis• Cell is making proteins and
organelles• DNA IS COPIED
– G2 phase = second gap• Cell is making proteins and
organelles
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Mitosis• 5 subphases:
– Prophase– Prometaphase– Metaphase– Anaphase– Telophase
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What happens in each phase
• At the end of interphase:– DNA has been copied– DNA not in chromosomes yet– Nucleus intact– The centrosome (an organelle
that helps organize the mitotic spindle fibers) replicates
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What happens in each phase• Prophase:
– Chromosomes now tightly coiled– Sister chromatids joined together– Nucleoli disappear– Mitotic spindle begins to form
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What happens in each phase• Prometaphase:
– Nuclear membrane breaks up– Microtubles from spindle start to connect with
chromosomes– Each sister chromatid has a kinetochore protein in
the centromere where the spindle fiber attaches
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• What is the primary difference between prophase and prometaphase?
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What happens in each phase
• Metaphase:– The spindle fibers push
the sister chromatids until they are all lined up at the metaphase plate (the middle of the cell)
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What happens in each phase
• Anaphase:– The sister chromatids are pulled apart by
the spindle fibers
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What happens in each phase• Telophase:
– New daughter nuclei begin to form around each set of chromosomes
– Chromosomes start to unwind
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Quick Think
Explain what happens to the chromosomes
during mitosis
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What happens in each phase
• Cytokinesis:– Division of the
cytoplasm– In animal cells, the
two new cells “pinch” apart
– In plant cells, a new cell wall forms between the 2 new daughter cells
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What phase is this cell in?
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Mitosis Modeling
• One chromosome before the DNA has been copied
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Mitosis Modeling
• 2 chromosomes AFTER the DNA has been copied
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Mitosis Modeling
• 1 sister chromatid
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Mitosis Modeling
• Centromere
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Mitosis Modeling
• Interphase – G1
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Mitosis Modeling
• Interphase – S
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Mitosis Modeling
• Interphase – G2
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Mitosis Modeling
• Prophase
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Mitosis Modeling
• Prometaphase
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Mitosis Modeling
• Metaphse
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Mitosis Modeling
• Anaphase
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Mitosis Modeling
• Telophase
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Mitosis Modeling
• Cytokinesis
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Chromosome Challenge!
• With your chromosomes….show me:
• Metaphase
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Chromosome Challenge!
• With your chromosomes….show me:
• Early Anaphase
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Chromosome Challenge!
• With your chromosomes….show me:
• Late Anaphase
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Chromosome Challenge!
• With your chromosomes….show me:
• End of Telophase
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Chromosome Challenge!
• With your chromosomes….show me:
• A cell before it has copied the DNA
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Chromosome Challenge!
• With your chromosomes…show me:
• All four stages with the people in your row…in order