Biology

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DNA

Structure:

DNA is formed of two strands coiled around eachother to form a double helix, these strands are joined by complementary base pairings, joined by hydrogen bonds. These bases are Adenine with Thymine, and Cytosine with Guanine.

Discovery:

Rosalind Franklin used x-ray christallography to discover DNA's helical two stranded structure.

James Watson and Francis Crick used this to make te first model of DNA.

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Protein Synthesis

A gene is a section of DNA that codes for a protein

Transcription:

In the nucleus of a cell, DNA unzips and one strand is copied into messenger mRNA, with Thyine being replaced with Uracil. The messenger mRNA then leaves the nucleus and into the cytoplasm.

Translation:

Translation occurs in the cytoplasm of cells, the mRNA attaches to a Ribosome, where each three bases re 'read'. The tRNA then fetch the corresponding amino acid, which is brought back to  the Ribosome where it is attached to all of the other amino acids, forming a protein.

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Enzymes

Enzymes are the catalysts produced by your body, they are also proteins

A catalyst is a substance that increases the speed of a reaction, without being used up in the process

Splitting/Joining substrates:

Every enzyme has a specific active site, this is the exact shape of the substrate that will be broken apart. The job of the active site is to join the enzyme and the substrate so it can be broken apart.

Conditions:

Temperature can change th rate of enzyme reactions, is it is too cold, the enzymes will have less energy to find and bind with their substrate slower. However, if it is too hot, the enzyme will become denatured, which means the active site will no longer bind with the substrate.

Ph - If the Phis too high or low, it interferes with the bonds holding the enzyme together, so it will denature

Substrate Concentration - The higher the concentration of substrates, the more likely it is for the enzyme to meet with the substrte, but it is only a limmiting factor up to a point - if all active sites are being used, adding more substrates will make no difference

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Human Genome Project

The Human Genome Project mapped out the 25,000 or so human genes.

Pros:

Predict and Prevent diseases

Develop new and better medicines more tailored to the person

More accurate diagnosis

Improve forensic science

Cons:

Increased Stress - If people think they'll get  disease, they'll be more worried about getting it

Gene-Ism - Peoplle pressured into not having kids if tthey have genetic problems

Discrimination by Employers and Insurers

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Genetic Engineering

Genetic Engineering uses enzymes to 'cut and paste' genes to mass produce a desirable gene, for example insulin. The useful gene is cut out of a human's DNA by enzymes and is inserted by enzymes into the plasmid DNA of a bacteium, the bacteria double in size in twenty minutes so can beusd to mass produce insulin.

Other uses include producing Golden Rice which is used to make fewer people suffer vitamin A deficiency.

However, producing too many GM organisms would reduce biodiversity, and also too much use of for example a herbicide, could lead to a weed that was resistant to it.

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Mitosis and Meiosis

Mitosis:

Mitosis is used for growth and repair. It results in two indentical, diploid daughter cells.

Firstly, DNA is replicated in the nucleus of a cell. The chromasomes then line-up in the middle of the cell where they are pulled apart, the cell then divides creating two identical, diploid daugther cells. This is used for Asexual Reproduction. This reults in exact clones oof the prent cell

Meiosis:

Meiosis is used to form haploid gametes, and results in variation.

The first division is exactly the same as mitosis, but after the first division, th chromasomes line up in the middle of the cell when they are split up, and the next division results in four total daughter cells that are haploid.

As this produces variation, it is a huge advantage of sexual reproduction over asexual reproduction.

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Mitosis and Meiosis

Mitosis:

Mitosis is used for growth and repair. It results in two indentical, diploid daughter cells.

Firstly, DNA is replicated in the nucleus of a cell. The chromasomes then line-up in the middle of the cell where they are pulled apart, the cell then divides creating two identical, diploid daugther cells. This is used for Asexual Reproduction. This reults in exact clones oof the prent cell

Meiosis:

Meiosis is used to form haploid gametes, and results in variation.

The first division is exactly the same as mitosis, but after the first division, th chromasomes line up in the middle of the cell when they are split up, and the next division results in four total daughter cells that are haploid.

As this produces variation, it is a huge advantage of sexual reproduction over asexual reproduction.

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