Biology- Unit 2- DNA and meiosis- The cell cycle

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  • Created by: FireDwarf
  • Created on: 31-01-14 21:23
What are the two stages of cell divison?
Nuclear division and cell division
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When the nucleus divides, examples mitosis and meiosis
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Cell division?
When the entire cell divides and this follows nuclear division.
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what must happen before a nucleus divides?
It must replicate its DNA, to ensure the daugther cells are capable of producing the protiens it needs.
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What is the fancy name given to this proccess?
Semi-conservative replication
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The proportion of DNA which is being copied is unravelled. The enzyme DNA helicase then breaks the H bonding between complementory organic base pairs between the two polynucleotide strands.
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This causes the two polynucleotide strands to be seperate. Each strand then must pair with free nucleotides, with complementory organic bases.
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What must be given for that to occur?
Energy, to activate the free nucleotides.
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H bonds form between the organic base pairs, and the enzyme dna polymercase ensures the nucleotides join together via condensation reactions.
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What has overall occured?
The original 2 strands become seperate and each individual strand has a replicated second strand which is now bonded.
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why is it called semi-conservative?
because half of the original DNA molecule has been conserved, while the other half has been replicated.
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What is mitosis?
A nuclear division which produces two daughter cells which are genetically identicial, thus having the same number of chrmosomes (diploid)
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What are the four stages of mitosis?
Interphase, prophase, metaphase, anaphase, telophase
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Cell makes a copy of its chromosomes via semi-conservative replication. Cell grows and ungoes normal functions.
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Chromosomes coil and become shorter and fatter. They are now visible. Nuclear envolope disspears. Nucleolous disspears.
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Chromosomes line up in the center of the cell. Spindle fibres attatch to the centrimere of the sister chromatids.
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The centrimere divides. The spindle fibres then contract which pulls each chromatid to opposite poles of the spindle.Now refered to as chromosomes.
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Where are spindle fibres produced from?
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Seperate chromosomes collect at opposite ends of the cell. New ncuelar envolope forms around them& nucleolous forms. Spindles disintergrate. Cell division then begins to commence.
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What is cell division labelled as?
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What are the 3 stages of the cell cycle? (and 3 stages of stage 1)
Interphase, Nuclear division, cell division. First stage (interphase breaks down into G1,S,G2)
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G1? S? G2?
First growth, G1, protiens from which the cell organelle are sythessised are produced. S, DNA replicated, G2, Organelle grow and divide and energy stores increased.
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What is cancer?
Growth disorder in cells, causing uncontrollable cell division. If gene gets effected which controls, occurs.
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How to be prevented?
Stop cell division.
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When the nucleus divides, examples mitosis and meiosis

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Cell division?


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Card 4


what must happen before a nucleus divides?


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What is the fancy name given to this proccess?


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