Protein Synthesis Chapter 13

Protein Synthesis  How does your DNA eventually lead to your different phenotypes (hair color, eye color, etc)

RNA  RNA is a nucleic acid (like DNA) which is made up of nucleotides EXCEPT its sugar is ribose instead of deoxyribose and it has Uracil instead of Thymine. Bases: Adenine (A), Guanine (G), Cytosine (C), & Uracil (U) that bonds with A in RNA

RNA  RNA is also only single-stranded, while DNA is double- stranded.

Three types of RNA  1. Messenger RNA (mRNA) – carries genetic information from DNA in the nucleus out to the ribosomes in the cytoplasm.

Three types of RNA  2. Transfer RNA (tRNA) – single chain folded into a hairpin shape that binds to specific amino acids

Three Types of RNA  3. Ribosomal RNA (rRNA) – Proteins are assembled on ribosomes which are made of subunits. These subunits are made of several ribosomal RNA.

Protein Synthesis  Protein Synthesis = Transcription + Translation

Steps of Transcription  1. Sections of DNA unzip, exposing the base pairs, by using RNA polymerase.  2. Pieces of mRNA come to the DNA strand and match to the proper base starting at the promotor region. ***Note – Uracil takes the place of Thymine and bonds to Adenine

Steps of Transciption  3. This continues until a complete strand of mRNA is made

RNA Editing  mRNA sometimes needs a bit of editing before it is able to be read (kind of like the rough draft of a term paper!)  Introns are portions of the mRNA that are cut out before it leaves the nucleus.  Exons are the remaining portions that are spliced back together to form the final mRNA strand.

Translation  Translation = the process by which mRNA is converted into a string of amino acids (building blocks of protein)  Translation happens in the ribosomes floating in the cytoplasm

Steps of Translation  1. mRNA strand from transcription breaks away from the DNA & moves into a ribosome floating in the cytoplasm.  2. Floating in the cytoplasm are loose tRNA pieces that contain an anticodon – a sequence of 3 nucleotides

Steps of Translation  3. tRNA anticodons match up with their complementary codons on the mRNA molecule. The tRNA brings along the correct amino acid  4. A chain of amino acids is joined to make a specific protein.

Codons and Anticodons  A codon specifies a particular amino acid  Both codons and anicodons are sequences of three base pairs.  Example: AUG or UAG or CGA  AUG signifies the start of an amino acid sequence.

Final Product = Proteins  Proteins – organic molecules made up of amino acids.  There are 20 amino acids  Proteins do such things as control biochemical pathways, direct the production of lipids, and take responsibility for cell movement.

Protein Synthesis Animation  Protein Synthesis Animation Protein Synthesis Animation Protein Synthesis Animation