Biology AS AQA Unit 2 DNA and Meiosis

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:44

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DNA and Meiosis
It is an information carrying molecule.
DNA strand is a polymer of nucleotides.
A DNA molecule is made from two strands.
The strands run antiparralel with each other.
It has hydrogen bonds.
Has a deoxyribose phosphate backbone to protect the
bases and make the molecule more…

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Copy of exact DNA.
Daughter DNA built from new molecules of deoxyribose, phosphate and organic bases.
Could lead to mistakes which would lead to mutation of proteins.

Both strands of DNA molecule act as template for attachment of nucleotides.
Enzyme DNA polymerase catalyses the reaction (ATP needed)
Enzyme DNA…

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DNA doubles.
Organelles replicate.
Protein synthesis occurs.

Chromosomes become visible.

Chromosomes attach to spindle at
the centromere.

Chromosomes lining up on the

Chromosomes migrate to
opposite poles.

Chromosomes disintegrate.
Daughter nuclei form at poles,
Spindles disintegrate and cells
about to divide.…

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Uncontrolled cell division
A single cell loses its mitosis control mechanisms due to mutation in ONCOGENES and divides without

Normal cells stay in G stage until given a specific signal to enter s phase.
Cancer phases has S phase without a signal.

Normal cells are mortal and divide…

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1. Homologous chromosomes (one maternal, one paternal) pair up and their chromatids wrap
round each other. Crossing over of the chromatids may occur. One chromosome from each
pair goes into one of the 2 daughter cells.
2. The chromatids move apart. Four cells have been formed (humans…


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