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B1 Cell Division (Plant cloning (Meristem cells can be cloned to be…
B1 Cell Division
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DNA
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Human body cells have 46 chromosomes, in 23 pairs
Each chromosome in a pair carries the same types of genes, 23rd pair are sex chromosomes
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Cell Cycle
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Length of time in phase = observed number of cells at stage / total number of cells observed x total length of time of cell cycle
Specialised plant cells
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Spongy mesophyll - Allow gases to circulate for exchange between leaf and environment, some photosynthesis
Guard cells - Open and close to control gas exchange: CO2, water vapour and oxygen
Sieve tubes - Transport photosynthesis products, including sugars and amino acids to where they are needed
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Animal systems
Circulatory - Transport substances, defend the body and regulate temperature
Excretory - Remove waste products and unwanted substances, regulate water content
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Skeletal - Bring about movement, support and protect internal structures, produce blood cells, store and release calcium
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Human stem cells
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An embryo develops from a fertilised egg, so stem cells can be collected from embryos in early development stages
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Adult stem cell locations - brain, eyes, blood, heart, liver, bone marrow, skin and muscle
Adult stem cells can only differentiate into related cell types, like bone marrow into blood and immune system cells
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Stem cell uses
They can be used to transplant into patients to treat conditions and disease such as through replacing cells
Conditions that can be treated: type 1 diabetes, multiple sclerosis, spinal cord or brain injuries
Embryonic stem cells from a 5 day old embryo are ideal but are difficult to obtain and there are ethical issues
Bone marrow transplants can be used to treat blood cell cancer or when blood cells have been destroyed
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Culturing microorganisms
- Sterilise all petri dishes, nutrient broth and agar
- Heat inoculating loop with a bunsen burner to sterilise
- Attach the lid of the Petri dish using adhesive tape
- Place agar plate upside into incubator to prevent moisture dripping onto the bacteria
- Incubate bacteria at 25 degrees to reduce chances of harmful bacteria
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Stem cell ethical issues
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Embryos may be seen as a commodity, not as something that could develop into a person
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Bacterial division
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Binary fission can happen once every 20 minutes if there's enough nutrients and the temperature is suitable
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