DNA and Genes

DNA contains genes which are instructions for proteins

• Genes are sections of DNA. They are found on chromosomes.
• Genes code for proteins (polypeptides) - they contain the instructions to make them.
• Proteins are made from amino acids.
• Different proteins have a different order and number of amino acids.
• It's the order of nucleotide bases in a gene that determines the order of amino acids in a particular protein.
• Each amino acid is coded for by a sequence of three bases (called a triplet) in a gene.
• Different sequences of bases code for different amino acids.
• The base sequence of a gene determines the amino acid sequence in a polypeptide)

Not all DNA in eukaryotic cells codes for proteins

• Genes in eukaryotic DNA contain sections that don't code for amino acids.
• These sections of DNA are called introns (all the bits that do code for amino acids are called exons).
• Introns are removed during protein synthesis. Their purpose isn't known for sure.
• Eukaryotic DNA also contains regions of multiple repeats outside of genes.
• These are DNA sequences that repeat over and over (e.g. ccttccttcctt)
• These areas don't code for amino acids either.

The nature and development of organisms is determined by genes

• Enzymes speed up most of our metabolic pathways - chemical reactions that occur in the…