RNA and Protein Synthesis

Central Dogma (idea) DNA  RNA  Proteins Replication Transcription Translation  Protein Synthesis Proteins are used to build cells and do much of the work inside cells

The Structure of RNA RNA, like DNA, is made up of nucleotides However, there are 3 differences between DNA and RNA: RNA has Ribose instead of Deoxyribose RNA has Uracil instead of Thymine RNA is Single-stranded instead of Double-stranded

3 Types of RNA Messenger RNA (mRNA) – carries the message from the DNA to the ribosomes Ribosomal RNA (rRNA) – make up part of the structure of a ribosome Transfer RNA (tRNA) – transfers amino acids to the ribosomes

Protein Synthesis

Transcription Making RNA from DNA (in the nucleus) DNA helicase unzips the DNA stand RNA polymerase binds to a special region of DNA called a promoter The RNA polymerase then attaches to the DNA strands and uses it as a template to build the mRNA A will now pair with U, T still pairs with A C and G still pair with each other

Transcription

Practice Transcription… DNA – AGC-TCC-GAT-GCA-TAC-TTG RNA – UCG-AGG-CUA-CGU-AUG-AAC DNA – GCC-AGT-GCT-TAC-GAA-CTG RNA – CGG-UCA-CGA-AUG-CUU-GAC

RNA Editing RNA requires a little editing before it is ready to go to the ribosome to make proteins Introns – sections of RNA that do not code for a protein (“in the way”) Cut out Exons – sections of RNA that do code for a protein (“expressed”) spliced back together

RNA Editing

Translation

Translation Making the proteins from the mRNA (“translating the code”) Occurs on the ribosomes

Translation mRNA must be transcribed from the DNA in the nucleus and released into the cytoplasm The mRNA attaches to the ribosome Start Codon is AUG (this tells the ribosome where to start translation) ADD TO YOUR NOTES The tRNA brings the proper amino acid to the ribosome Anticodon – sequence of bases on the tRNA that pair with the mRNA

Translation The amino acids form a peptide bond to hold them together The next amino acid is brought in and is attached This continues until the ribosome reaches a stop codon The completed protein is then released

Translation

The Genetic Code Proteins are made of amino acids There are 20 different amino acids A codon is a 3 base sequence that codes for a specific amino acid There are 64 possible codons

The Genetic Code

Another way to read the codons

The Genetic Code mRNA sequence: UCGCACGGU Separate into codons (groups of 3 bases): UCG-CAC-GGU Identify the amino acids: Serine-Histidine-Glycine

Mutations

Mutations Changes in the DNA sequence that affect genetic information Gene mutations – result from changes in a single gene Chromosomal mutations – involve changes in whole chromosomes

Gene Mutations Frameshift or Point mutations – a mutation that occurs at a single point (only 1 nucleotide is changed) Substitution – a single nucleotide is substituted for another one (A instead of G) Insertion – a single nucleotide is added Deletion – a single nucleotide is removed

Gene Mutations Insertions and deletions cause frameshift mutations because they shift the “reading frame” of the genetic message.

Chromosomal Mutations Deletion – a section of a chromosome is deleted Duplication – a section of a chromosome is copied and inserted Inversion – a section of a chromosome is moved from one spot to another Translocation – a piece of a chromosome is moved from one chromosome to another

Chromosomal Mutations