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Published byMatilda Welch Modified over 9 years ago
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Cell Growth & Division What problems does growth pose for cells?
My sisters keeper 9 -11min (Diagnosis) 23:30-29 (Mom- shaves head feel bad for pain she caused to everyone) 41: :35 (she meets taylor
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Why do cells need to be small?
DO NOW Why do cells need to be small?
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Why do cells need to be small?
Trouble moving enough nutrients and wastes across the cell membrane Organization The larger a cell becomes, the more demands on its DNA
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SA to Volume Ratio plays a role in determining cell size
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Purpose of cell division?
We start out as one cell! We need to make more and more cells until we have about one hundred trillion!
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Before it divides condenses into chromosomes
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Chromosomes Chromosome number is unique to every species
Humans: 46 chr. Chimpanzees: 48 chr. Yeast: 32 chr. Adders-Tongue Fern: 1440 chr.!
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Quality of the Genetic Material and NOT the Quantity
Moral: Quality of the Genetic Material and NOT the Quantity give an organism complexity
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23 THESE HAVE BEEN DUPLICATED- look closely
Humans have 46 chromosomes- 23 from mom/ 23 from dad Hey Mom thanks for the 23 chromosomes REMINDER: each coil DNA that are the instructions for our traits 23
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Chromosomes Humans have 46 chromosomes in every cell
During S-phase of the cell cycle, all 46 are copied When the cell splits in half, each new cell has the exact same chromosome # as before
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MITOSIS Daughter Parent Cell Cells
1:30 seconds Why cant a cell just split into two? Parent Cell to daughter cells- Note daughter cells look genetically identical to parent cells DNA replication
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Checkpoints G1 Checkpoint: G2 Checkpoint M checkpoint Cell size
DNA can be replicated G2 Checkpoint DNA intact DNA duplicated M checkpoint - Chromosomes are properly attached to the spindle fibers.
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What happens if the cell cannot pass through the checkpoint?
Repair the damage OR 2. Self-destruct APOPTOSIS (Programmed Cell Death) Stop here !!
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1. Gap 1 cell grows, doubles organelles
I. Interphase: 90% of the time! 1. Gap cell grows, doubles organelles 2. Synthesis Duplication of the DNA 3. Gap cell grows
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Steps of Mitosis: (PMAT)
MITOSIS : NUCLEAR DIVISION During Mitosis the movement of the chromosomes (DNA) are guided by spindle fibers which are long proteins that grow from the centrioles (in animal cells) or the membrane (in plant cells). Steps of Mitosis: (PMAT) Prophase Metaphase Anaphase Telophase
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1. Prophase- Chromatin fibers condense Nuclear membrane breaks down
Spindle of microtubules forms from centrioles [animals only]
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2. Metaphase- “middle” Spindle fibers from centrioles attach to centromeres Spindles move Chromosomes to line up in the middle Centriole Spindle
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3. Anaphase: “away phase”, form “A’s”
Spindle fibers contract Pull sister chromatids apart Chromosomes move towards opposite ends Each side has own copy of DNA Individual chromosomes
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4. Telophase- “end phase”
Nuclear membranes reform at each pole Chromosomes unwind Spindle disappears
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(NOT a phase of Mitosis)
Cytokinesis (NOT a phase of Mitosis) During cytokinesis, the cytoplasm cuts in half Each daughter cell has an identical set of duplicate chromosomes
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Cytokinesis in Plants In plants, a structure known as the cell plate forms midway between the divided nuclei. No centrioles attach to cell wall
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Cytokinesis in Animals
Animal cells contract an actin fiber across middle of cell and “pinch” into 2 new cells. - called a “cleavage furrow”.
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Cancer Cells… - Do not stop dividing when they contact other cells - Do not respond to signal and divide uncontrollably - Don’t stop at checkpoints and do not do apoptosis - Form masses of cells called tumors - Metastasis: tumor cells break loose and spread in body
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Contact Inhibition Normal cells will reproduce until they contact other cells. When this happens, they stop growing.
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How are cancer cells different from other cells?
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Tumors - mass of cancer cells
Tumors - mass of cancer cells. The cells attract new blood vessel growth (this is called angiogenesis)
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Causes of Cancer/Carcinogens
Random Mutations Genetics Chemicals- asbestos, cigarettes, formaldehyde, pesticides, nitrates Radiation Certain viruses (HPV) Poor Diet/ Obesity
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Prevention of Cancer Genetic screening BRCA 1 and BRCA 2 Do not smoke
limit alcohol consumption Maintain a proper diet exercise prevent sunburns Get Proper health screenings
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Mutations typically happen in two types of genes 1
Mutations typically happen in two types of genes 1. Proto-oncogenes are normal genes that regulate cell growth Oncogenes are mutated proto-oncogenes 2. Tumor suppressor genes – genes that stop the cell cycle or promote apoptosis ex. p53 gene
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p53 gene, Tumor suppressor gene "guardian of the genome", usually functions to properly control the cell cycle p53 is mutated in over 50% of all human cancers.
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Biopsy- way to diagnose cancer by surgically
removing piece of tissue and examining it Staging - Describes the severity of a person’s cancer - Aids in planning the treatment
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MEIOSIS Sperm and egg.
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Meiosis - the production of haploid cells with unpaired chromosomes - word means "to diminish".
-process creates gametes (sperm and eggs), cells that are haploid (1N) -gametes combine to create a zygote which is diploid (2N)
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Meiosis is actually TWO divisions, this results in FOUR daughter cells, each with HALF the number of chromosomes. These cells are HAPLOID!
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Homologous Chromosomes
- each chromosome has a match, called a homolog. This is why normal organisms always have an even number of chromosomes. Chromosomes are numbered and paired according to their size. Karyotype showing homologous pairs.
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Why Meiosis increases Genetic Variation
During Prophase I - homologous chromosomes pair up and exchange DNA. - this is called CROSSING-OVER
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During metaphase, chromosomes line up in PAIRS, but they line up randomly. This picture shows all the different possible arrangements for an organism with 6 chromosomes. This is called INDEPENDENT ASSORTMENT
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Fertilization = combining the genes of two different parents.
When gametes combine, offspring show variation due to independent assortment and crossing over
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The Phases of Meiosis Similar in plants and animals. Plant cells lack centrioles.
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Meiosis creates gametes (sperm and eggs)
Meiosis ensures variability in offspring Gametes combine to create a zygote which is diploid (2N) - process of sexual reproduction
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Figure 10.9a
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3 small polar bodies are formed
During OOGENESIS, cytoplasm divides unevenly during each cytokinesis, resulting in only ONE viable egg cell. 3 small polar bodies are formed 1 large OOCYTE has potential to be fertilized
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The process results in 4 daughter cells Daughter cells are haploid (N)
Key points of Meiosis The process results in 4 daughter cells Daughter cells are haploid (N) Daughter cells have unique combinations of chromosomes
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Check for understanding
1. What phase directly follows metaphase I? 2. How many cells are present at the end of meiosis I ? 3. A cell has a diploid number of 60, what is the organism's haploid number? 4. Meiosis occurs in what type of cells? 5. In what phase do homologous chromosomes pair up and crossing-over can occur? 6. In what phase do the CHROMATIDS separate? anaphase I 2 30 gametes prophase 1 anaphase 2
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Pg 180 Which of these pictures is metaphase I of MEIOSIS and which is metaphase of MITOSIS? Mitosis Meiosis
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Mitosis Videos
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Twilight DOES IT TOO!
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