Cell Division

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DNA

DNA =

  • Deoxyribose
  • Nucleic
  • Acid
  • Contains the "instructions" to put an organism together and make it work.
  • It's found in the nucleus of and animal and plant cells.
  • It's comes in really long molecules called chromosome.

Genes:

  • A gene is a section of DNA.
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Mitosis

Mitosis is asexual cell reproduction

  • Body cells normally have two copies of each chromosome, however with mitosis they don't.
  • When a body cell divides it needs to make new cells identical to the original cell.
  • This type of cell division is called mitosis.

 

Process of mitosis:

  • In a cell that's not dividing the DNA is in long strings.
  • If the cell is going to divide it duplicates its DNA to form x-shaped chromosomes.
  • The chromosomes then line up in the center of the cell, and get pulled apart.
  • Membranes form around each of the sets of chromosomes. These become Nuclei of the two cells.
  • The cytoplasm divides
  • You have two new identical cells carrying the same DNA
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Meiosis

Meiosis is a sexual cell reproduction

 During sexual reproduction, two cells called gametes combine to form a new individual.

  • Gametes only have one copy of each chromosome.
  • This is because you have a cell from the mother and a cell from the father and still have the same number of chromosomes, for example the human body cells have 46 chromosomes.
  • The new individual will have a mixture of two sets of chromosomes, so it will inherit features from the mother and the farther.

Process of meiosis:

  • Before the cell starts to divide, it duplicates its DNA. one arm of each chromosome is an exact copy of the other arm.
  • In the frst devision in meiosis, the chromosome pairs line up in the center of the cell.
  • The pairs are then pulled apart, so each new cell only has one copy of each chromosome.
  • In the second division the chromosomes line up again in the center of the cell.like mitosis the arms are pulled apart.
  • You get four gametes each with only a single set of chromosomes in it.
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Stem Cells

  • Differentiation is the process by which a cell changes to become specialised for its job.
  • Some cells are undifferentiated. They can develop into different types of cell depending on what instructions they're given. These cells are called stem cells.
  • Stem cells are found in early human embryos, they have the potential to turn into any kind of cell.
  • Medicine already uses adult stem cells to cure diseases.
  • Scientists can also extract stem cells from very earl human embryos and grow them.
  • Some people are against stem cell research because they feel that human embryos shouldn't be used for experiments since each one is a potential human being.
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