DNA Notes

DNA Basics A long molecule made of strand of the bases A, T, C and G Sections of genes are in DNA that make specific proteins Sequence of bases control which amino acids are made and joined to create a new protein or enzyme molecule   Enzymes: Large molecules that speed up chemical reactions in cells. Each enzyme does one specific job.

Aerobic Respiiration Most of our energy comes from this It takes place in the mitochondria of cells Mitochondria are oval structures in the inner membrane Occur in liver and muscle cells that require a lot of energy 

Enzyme Structure Soluble protein molecules that speed up chemical reactions in cells  Like all proteins they consist of a string of different amino acid sub units Amino acids must be in correct sequence for the enzyme to work Sequence Controlled by genetic protein for the code, codes held in DNA molecules 

DNA  DNA molecules are very long but packed with chromosomes Each molecule consists of two twisted strands of bases, they form a double helix Two strands held together by hydrogen bonds between the bases When the cell grows it divides into two. The DNA molecules must duplicate by: bonds breaking between the two strands then new bases joining each old strand to make new strands.

Genetic Code A bonds with T and C bonds with G Makes it possible to predict the order of bases

Genetic Code

Extracting DNA from cellsPossible in several ways, the simplest is: Salt water, detergent and peas are mashed together Mixture left for 15 mins at 60ºC   Filter the mixture and pour iced ethanol on to the filtrate DNA rises to the surface

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The discovery of DNA 20th century: Scientists tried to study DNA 1950: two scientists, Rosalind Franklin and Maurice Wilkins used x-rays to produce a photo of DNA This photo allowed James Watson and Francis Crick to work out the 3D structure of DNA - A double helix

The human genome project (HGP) Aimed to work out the order of 3 billion base pairs in a humans genome To develop faster methods to sequence DNA To discover all genes 2001: sequencing project finished but still working on identifying all genes in the genome Involved scientists from 18 different countries and showed how scientists collaborate We all have different DNA unless your an identical twin so they predicted a average DNA sequence

Genetic engineering  Certain enzymes are cut from DNA from one organism and joined into the gap of another organisms DNA New organism with inserted genes has one or more new characteristics New organism could produce a useful substance or perform a new function We say this organism has been genetically engineered Used to produce insulin: human cell that makes insulin cut and a small slot from plasmid in bacterium is cut. The human insulin gene is put into the plasmid which multiplies and creates insulin

For genetic engineeringProduces useful genetically modified animals and plants including: Sheep produce genes to treat the symptoms of cystic fibrosis (a disease which causes sufferers to produce abnormally thick and sticky mucus in their lungs, leading to many health problems) and creates insulin for diabetic people Tobacco plants that glow on the dark when they need watering  Some people are excited by the almost limitless possibilities Against genetic engineering Some people say its unethical and should be banned: We don't know the effects it could have on animals and plants in the future If it was in the wrong hands it could be used badly

Wild Rice Rice that has a extra gene that produces beta carotene Beta carotene is needed by humans to make vitamin A  Used in areas where Vitamin A deficiency (third world countries) is common and so can help prevent blindness This is bad because: it could crossbreed and contaminate wild rice; GM foods could harm people; beta carotene aren't high enough to make a difference and GM foods are expensive

GM Insulin Natural insulin taken from pig or cow pancreas is limited in supply and doesn't suit everyone Its now made synthetically (man made or non natural) Used to produce insulin: human cell that makes insulin cut and a small slot from plasmid in bacterium is cut. The human insulin gene is put into the plasmid which multiplies and creates insulin This is good because: its easier to make; more of it; less likely to cause adverse reaction and overcomes ethical concerns 

Herbicide resistant crops Added genes to crop plants that make them resistant to herbicides Reduces the quantity of herbicide that needs to be used This is bad because: the potential development of herbicide-resistant weeds and kills species of weed that feed animals

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