B5- Growth and Development

B5- Growth and Development: Revision Notes:DNA- The DNA molecule is a double helix, the strands of DNA are made up of units linked by chemicals called bases. There are 4 bases A, T, C and G which always have to pair up in the same way so A with T and C with G. The order of bases in a gene makes up the genetic code. This is the code that gives instructions for the assembly of a protein.Protein synthesis-In plant and animal cells, the genetic code that carries the instructions for protein synthesis is on the DNA in the nucleus. Protein synthesis occurs in the cytoplasm. Genes do not leave the nucleus, so in order to carry the genetic code to the cytoplasm, messenger RNA (mRNA) is produced in the nucleus, using DNA as the template (during which time the two stands of the DNA separate). Proteins are assembled on organelles in the cytoplasm called ribosomes.

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