The Central Dogma … From DNA to proteins

How your cell makes proteins… The synthesis (production) of proteins: 2 phases Transcription Translation DNA  RNA  Protein

Before making a protein… Your cell must first make RNA How does RNA differ from DNA? DNA RNA Deoxyribose sugar Ribose sugar Thymine (T) Uracil (U) Double stranded Single-stranded

Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) Carries instructions from DNA to ribosome and tells it what kind of protein to make Transfer RNA (tRNA) Brings amino acids to ribosomes during proteins synthesis Ribosome RNA (rRNA) Guides the translation of mRNA into protein All are produced in the nucleus!

If the cell were Westlake… Nucleus – Main office Nucleolus – Mrs. Bates’ office DNA – Mrs. Bates Ribosomes – Cafeteria ladies mRNA – email that Mrs. Bates sends to the lunch ladies to tell them what to make

Transcription (DNAmRNA) RNA molecules are produced by copying part of a DNA strand into a complementary sequence of RNA (remember – U replaces T!!) The process is started and controlled by an enzyme called RNA polymerase

Transcription Animation

Translation The process of making proteins from mRNA – takes places in ribosomes The sequence of mRNA bases determines the amino acid sequence of a protein There are 20 amino acids

Translation Each series of THREE (3) mRNA bases is called a CODON and corresponds to a specific amino acid This is known as the genetic code tRNA molecules carry an amino acid at one end and an ANTICODON at the other The anticodon is made up of three bases that are complementary to codons on the mRNA strand Ex: AUG on mRNA = UAC on tRNA

Steps of Translation 1. Initiation Process begins at the start codon (AUG). AUG codes for the amino acid Methionine Met will be the first amino acid in this sequence

Steps of Translation 2. Elongation Individual tRNA molecules continue to carry amino acids to the ribosome and place them in the order determined by the mRNA sequence

Steps of Transloation 3. Termination The process of translation is completed when the ribosome reaches any one of the three STOP codons on the mRNA strand The stop codons are: UAA, UAG or UGA

Translation Animation Video Clip

Checkpoint: If given the anticodon ACC which belongs to the amino acid tryptophan, what would be the DNA base code for this amino acid?

The Codon Wheel

The Codon Chart: