RNA and Protein Synthesis Chapter 12.3a RNA and Protein Synthesis

Genes are coded DNA instructions that control the making of proteins within the cell. The first part of processing the genetic message is copying sequences of DNA into RNA.

The Structure of RNA RNA is made of a chain of nucleotides. There are 3 differences between DNA and RNA: The sugar in RNA is ribose, instead of deoxyribose in DNA. RNA is single-stranded while DNA is double stranded. RNA does not contain thymine (T) instead it has uracil (U).

Types of RNA There are 3 types of RNA: messenger RNA, ribosomal RNA, and transfer RNA. Messenger RNA carries the information from DNA out of the nucleus into the cytoplasm. Ribosomal RNA makes ribosomes. Transfer RNA is a molecule that brings the correct amino acid to the ribosome.

Transcription Transcription is the process where a part of DNA is made into RNA. Transcription requires RNA polymerase – this is an enzyme that binds to DNA and separates the DNA strands and uses one of the strands to make a strand of RNA. RNA polymerase needs to bind at the beginning of a gene. It knows where that is because there is a promoter – these are areas of DNA that have a specific sequence.

RNA Editing RNA molecules usually have introns and exons. Introns are areas on RNA that are not involved in coding for proteins. Exons are the parts that are essential for the protein. When RNA is made it has both introns and exons – before proteins are actually made the introns are cut out of the RNA strand. The remaining exons are then glued together to make the functioning gene.

The Genetic Code Proteins are made by putting together many amino acids into a long chain called a polypeptides. There are 20 different amino acids. 3 bases of RNA makes a codon that codes for a specific amino acid. For example: the strand UCGCACGGU would be broken into groups of 3 UCG – CAC – GGU Each of these groups of 3 codes for a specific amino acid – UCG codes for the amino acid serine, CAC codes for histidine, and GGU codes for glycine.