DNA - The Code of Life
• Nucleic acids (molecules of life) - controls synthesis of proteins & structure and functioning of
organisms
• Nucleic acids in cells:
- Deoxyribonucleic acids (DNA)
- Ribonucleic acid
Deoxyribonucleic acid:
• Francis Crick & James Watson
• Found in nucleus of cells & forms part of chromosomes that make up chromatin network
Chromatin: Chromosomal material made up of DNA, RNA and histone proteins as found in a non-
living cell.
• DNA coiled to t inside nucleus (2 metres long)
• Extranuclear DNA: Small amounts of DNA in mitochondria
• DNA molecule: 2 strands twisted into 3D double helix
• 46 chromosomes in a cell: (23 homologous pairs)
• DNA molecule = polymer made up of monosomes (nucleotides)
Histones: Proteins that chromosome material coils around
• Nucleotide made up of:
- Sugar molecule (deoxyribose)
, - Phosphate molecule
- Nitrogenous base: (adenine, thymine & guanine, Cytosine)
• 4 bases = foundation of genetic code
• 4 di erent bases = 4 di erent nucleotides
• Double helix made up of:
- 2 outer strands = chain of altering sugar links with strong bonds
- Rungs of helix = pairs of bases attached to sugar molecules (base can't attach to phosphate)
• Shape and size of 4 bases di er so that:
- Adenine and thymine bond by 2 hydrogen bonds (A double hydrogen bonded to T)
- Cytosine and guanine bond by 3 hydrogen bonds (C triple hydrogen bonded to G)
• 2 groups of nitrogenous bases:
- Purines: 2 fused rings of nitrogen, carbon and hydrogen atoms eg. Adenine and Guanine
- Pyrimidines: 1 ring of similar atoms eg. Thymine and Cytosine
• Base pair is always made up of 1 purine and 1 pyrimidine
• Base di erentiation in organisms:
- 4 nucleotides in di erent sequences
- Sequence of nucleotides determines genetic code
• Nucleic acids (molecules of life) - controls synthesis of proteins & structure and functioning of
organisms
• Nucleic acids in cells:
- Deoxyribonucleic acids (DNA)
- Ribonucleic acid
Deoxyribonucleic acid:
• Francis Crick & James Watson
• Found in nucleus of cells & forms part of chromosomes that make up chromatin network
Chromatin: Chromosomal material made up of DNA, RNA and histone proteins as found in a non-
living cell.
• DNA coiled to t inside nucleus (2 metres long)
• Extranuclear DNA: Small amounts of DNA in mitochondria
• DNA molecule: 2 strands twisted into 3D double helix
• 46 chromosomes in a cell: (23 homologous pairs)
• DNA molecule = polymer made up of monosomes (nucleotides)
Histones: Proteins that chromosome material coils around
• Nucleotide made up of:
- Sugar molecule (deoxyribose)
, - Phosphate molecule
- Nitrogenous base: (adenine, thymine & guanine, Cytosine)
• 4 bases = foundation of genetic code
• 4 di erent bases = 4 di erent nucleotides
• Double helix made up of:
- 2 outer strands = chain of altering sugar links with strong bonds
- Rungs of helix = pairs of bases attached to sugar molecules (base can't attach to phosphate)
• Shape and size of 4 bases di er so that:
- Adenine and thymine bond by 2 hydrogen bonds (A double hydrogen bonded to T)
- Cytosine and guanine bond by 3 hydrogen bonds (C triple hydrogen bonded to G)
• 2 groups of nitrogenous bases:
- Purines: 2 fused rings of nitrogen, carbon and hydrogen atoms eg. Adenine and Guanine
- Pyrimidines: 1 ring of similar atoms eg. Thymine and Cytosine
• Base pair is always made up of 1 purine and 1 pyrimidine
• Base di erentiation in organisms:
- 4 nucleotides in di erent sequences
- Sequence of nucleotides determines genetic code
