biology topic 21
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- Created on: 25-03-16 18:46
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- Biology Topic 2
- Fertillisation
- Term used to describe when nuclei of female and male gametes fuse
- For Animals
- 1. Sperm swim towards the egg cell in the oviduct
- 2. Once one sperm makes contact with the zona pellucida of the egg cell, the acrosome reaction occurs-This is where digestive enzymes are released from the acrosome of the sperm
- 3. These enzymes digest the zona pellucida, so that the sperm can move through it to the cell membrane of the egg cell
- 4. The sperm head fuses with the cell membrane of the egg cell. This triggers the cortical reaction- the egg cell releases from the contents of vesicles called cortical granules into the space between the cell membrane and the zona pellucida
- 5. The chemicals from the cortical granules make the zona pellucida thicken, which makes it impenetrable to other sperm. This makes sure that only one sperm fertilises the egg cell
- 6. Only the sperm nucleus enters the egg cell- its tail is discarded
- 7. The nucleus of the sperm fuses with the nucleus of the egg cell-HAZAH FERTILISATION!
- 6. Only the sperm nucleus enters the egg cell- its tail is discarded
- 5. The chemicals from the cortical granules make the zona pellucida thicken, which makes it impenetrable to other sperm. This makes sure that only one sperm fertilises the egg cell
- 4. The sperm head fuses with the cell membrane of the egg cell. This triggers the cortical reaction- the egg cell releases from the contents of vesicles called cortical granules into the space between the cell membrane and the zona pellucida
- 3. These enzymes digest the zona pellucida, so that the sperm can move through it to the cell membrane of the egg cell
- 2. Once one sperm makes contact with the zona pellucida of the egg cell, the acrosome reaction occurs-This is where digestive enzymes are released from the acrosome of the sperm
- 1. Sperm swim towards the egg cell in the oviduct
- Cell differentiation
- 1. Stem cells all contain the same genes, but not all of them are expressed because not all of them are active
- 2. Under the right conditions, some genes are activated and other genes are inactivated
- 3. mRNA is only transcribed from the active genes
- 4. The mRNA from the active genes is then translated into proteins
- 5. These proteins modify the cell-they determine the cell structure and control cell processes (including the activation of more genes, which produce more proteins)
- 6. Changes to the cell produced by these proteins cause the cell to become specialized (differentiate). These changes are difficult to reverse, so once a cell has differentiated it stays specilaized
- 5. These proteins modify the cell-they determine the cell structure and control cell processes (including the activation of more genes, which produce more proteins)
- 4. The mRNA from the active genes is then translated into proteins
- 3. mRNA is only transcribed from the active genes
- 2. Under the right conditions, some genes are activated and other genes are inactivated
- 1. Stem cells all contain the same genes, but not all of them are expressed because not all of them are active
- Stem cells
- Cell differentiation
- 1. Stem cells all contain the same genes, but not all of them are expressed because not all of them are active
- 2. Under the right conditions, some genes are activated and other genes are inactivated
- 3. mRNA is only transcribed from the active genes
- 4. The mRNA from the active genes is then translated into proteins
- 5. These proteins modify the cell-they determine the cell structure and control cell processes (including the activation of more genes, which produce more proteins)
- 6. Changes to the cell produced by these proteins cause the cell to become specialized (differentiate). These changes are difficult to reverse, so once a cell has differentiated it stays specilaized
- 5. These proteins modify the cell-they determine the cell structure and control cell processes (including the activation of more genes, which produce more proteins)
- 4. The mRNA from the active genes is then translated into proteins
- 3. mRNA is only transcribed from the active genes
- 2. Under the right conditions, some genes are activated and other genes are inactivated
- 1. Stem cells all contain the same genes, but not all of them are expressed because not all of them are active
- Totipotency- the ability to produce all cell types, including all the specialised cells in an organism and extraembryonic cells (cells of the placenta and umbilical cord)
- Pluoripotency- the ability of a stem cell to produce all specialized cells in an organism (but not extraembryonic cells)
- Unspecialized cells that can develop into any type of cell
- Medical uses
- Stem cell therapies
- Leukemia patients can have bone marrow transplants
- Spinal cord injuries
- Heart disease
- Damaged caused by heart attacks
- Save many lives
- Donor organs restocked fully
- Cure blindness-replaces old eye cells with cells created by newly formed eye cells
- Stem cell therapies
- Sources
- Adult stem cells
- Found in bone marrow
- Simple operation
- Little risk involved
- Not as flexible-Can only differentiate into a limited type of cells
- Embryonic
- Embryonic stem cells
- Obtained from early embryos
- Created in a laboratory using IVF
- 4-5 days old stem cells are removed
- Embryo is destroyed in process
- Can differetiate into all cell types
- Obtained from early embryos
- Adult stem cells
- Cell differentiation
- Fertillisation
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