the structure of DNA and protein synthesis

• DNA strands are polymers made up of many repeating units called nucleotides
• each nucleotide consists of a phosphate molecule, a sugar molecule and a base
• the sugar and phosphate groups in the nucleotides alternate
• the four possible bases in a nucleotide are A, G, C and T
• in nucleotides, the base always pairs to the sugar molecule
• base A always pairs up to base T and base G always pairs up to base C
• the order of bases in a gene decides the order of amino acids in a protein
• each amino acid is coded for by a sequence of threee bases in a gene
• amino acids produced in a cell are joined together to make various proteins, depending on the order of the gene's bases
• there are parts of DNA that don't code for proteins. some of these parts switch genes on and off, so they control whether or not a gene is expressed
• proteins are made in the cell cytoplasm in ribosomes
• to make proteins, ribosomes use the code in DNA
• mRNA is the molecule that copies the code from DNA and acts as a messenger between the DNA and the ribosome
• the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
• when a chain of amino acids has been assembled, it folds into a unique shape which allows the protein to perform the tast it's meant to do
• examples of proteins include: enzymes, hormones and structural proteins
• protein synthesis consists of two stages: transcription and translation