What is gene expression?

Gene Expression and Protein Synthesis The Genetic Code Gene-a section of DNA that codes for an amino acid sequence (on RNA), which is a building block for proteins.

Amino Acids and Codons

These three letter words are called codons Genes can be made up of 20 different amino acids made up of three letter words (four letters to choose from-nitrogenous bases of RNA [A, U, G, C]). These three letter words are called codons Example: Codon AUG, codes for methionine.

50 Cents favourite codon: UAG

Simple Summary DNA produces an RNA strand in the nucleus RNA single strand leaves the nucleus through a nuclear pore RNA enters cytoplasm RNA attaches to a ribosome RNA molecule is decoded/”read” and produce a protein

From DNA RNA Protein Step One: Transcription -RNA molecule is made that is complimentary to DNA molecule DNA sequence: AAGCT RNA complimentary sequence: UUCGA -RNA polymerase is the enzyme used to split apart the DNA and join the RNA nucleotides together -messengerRNA (mRNA ) is released into the cytoplasm and reaches a ribosome

transcription

2. Step Two: Translation: -The information on the mRNA is translated and codes for a specific amino acid (needed to make the polypeptide protein) Transfer RNA (tRNA)-attach to an amino acid and brings it to the ribosome (containing rRNA)

Steps of Translation Initiation: A start codon on mRNA, AUG methionine, allows translation to begin mRNA codon pairs with the complimentary tRNA anticodon Example codon on mRNA: AUG Anticodon on tRNA: UAC

Amino Acid tRNA Anticodon mRNA strand codon tRNA synthetase helps bind the amino acid to the tRNA molecule tRNA Anticodon mRNA strand codon

II. Elongation-polypeptide gets longer one amino acid at a time III. Termination-synthesis stops due to a stop codon The three stop codons on the mRNA strand are: ___, ____, ____ Refer to page 330 (or 299)

Just like a recipe that you follow…instead of eggs, its amino acids…instead of samosas, it’s proteins (gene expression)

DNA RNA Double strand Single strand Helix (spiral) Straight (Deoxyribonucleic Acid) RNA (Ribonucleic Acid) Double strand Single strand Helix (spiral) Straight Sugar present: deoxyribose Sugar present: ribose Nitrogen bases: Adenine, Thymine, Guanine, Cytosine Adenine, Uracil, Guanine, Cytosine (Uracil replaces thymine) Found in the nucleus Found in the nucleus and the cytoplasm (not confined in the nucleus)

Three Classes of RNA Messenger RNA (mRNA): Takes a message made from DNA in the nucleus to a ribosome in the cytoplasm

Ribosomal RNA (rRNA): A part of/embedded in the ribosome and the site in which polypeptides are made. (two subunits: small and large ribosome)

Transfer RNA (tRNA): Transfers amino acids to the ribosome (helps translate the message)

The tRNA synthetase (enzyme) recognizes which amino acid belongs to which tRNA molecule