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Summary DNA - Code of life - Life Sciences
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Summarised notes on Matric DNA - Code of Life from the Mind Action series Life Science textbook.
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Dna - The Code of LifeNucleic acids are the molecules of life
They control synthesis of protein which make up the structure of the body but (as enzymes) control chemical
processes in cells
2 nucleic acids:
1. Deoxyribonucleic acid (DNA)
2. Ribonucleic acid (RNA)
Deoxyribonucleic Acid - DNA
Discovered by:
- Maurice Wilkins
- Rosalind Franklin
- Francis Crick
- James Watson
Location
- Found mainly in the nucleus where it forms part of the chromosomes in chromatin network
- DNA is coiled to fit in nucleus with ± 2 metres in each cell
- Extranuclear DNA: DNA found in mitochondria (plants & animals) and chloroplasts (plants only)
Structure
- Long, twisted ladder to form double helix
- DNA is a polymer made up of nucleotides (monomers)
- Each nucleotide is made up of
- Sugar molecule - deoxyribose
- Phosphate molecule
- nitrogenous bases
- Adenine
- Thymine
- Guanine
- Cytosine
- The bases are the foundation of the genetic code instructing cells on how to synthesise enzymes &
proteins
, How the double helix is made up
- 2 outer strands formed by chain of alternating sugar/phosphate links with strong bonds
- Rungs of the ladder are from pairs linked by weak hydrogen bonds
- Base pairs attached to sugar molecules
Base pairing
- Shape & size differ so that:
- Adenine will bond with thymine or uracil (RNA) by 2 hydrogen bonds
- Cytosine will only bond with guanine by 3 hydrogen bonds
Classification
- 2 groups: purines & pyrimidines
- Purines: 2 fused rings of nitrogen, carbon & hydrogen atoms. (G & A)
- Pyrimidines: 1 ring of similar atoms therefore small than purines (T, C & U)
- Bases are made of 1 pyrimidine & purine
- Four nucleotides are the same in all organisms difference comes in the sequence of them
- If the sequence is the same then identical organisms
- Therefore the sequence of nucleotides determines the genetic code of an organism
Role of DNA
- Carry hereditary info in cells in the form of genes
- Provide blueprint for coding of protein synthesis
- Replicate to pass on genetic info to daughter cells during mitosis
Non-coding DNA
- Less than 2% of DNA codes the rest is non-coding DNA
- Protein-coding is aka exons which is interrupted by introns (non-coding)
- Complex organism have more introns than less complex organism
- Intron regions were thought to be ‘evolutionary junk’ but now are known to form functional RNA
molecules which have functions
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