2 Review of DNA DNA is a double Helix that is a code for something What?Structure/Shape explains how it is replicated, but not how genes work.Helicase and DNA PolymeraseChargaff’s RuleNucleotide5 Carbon Sugar (Deoxyribose), Phosphate and Nucleic Acid (Guanine, Cytosine, Adenine, Thymine)
3 First Step in Decoding Messages: Copy DNA (Deoxyribonucleic Acid) into RNA (Ribonucleic Acid)Note: “Deoxyribo” in Deoxyribonucleic Acid is in reference to the 5-Carbon Sugar in the backbone of the moleculeDeoxyriboseSo what do you think the 5-Carbon Sugar is in the backbone of Ribonucleic Acid?Ribose
4 Differences (Between DNA and RNA) DNA RNADeoxyribose RiboseDouble Stranded Single StrandedThymine Uracil
5 RNA is a disposable copy of DNA 3 Types of RNAmRNAMessengers – they carry copies of the instructions for proteins. (From Nucleus to Ribosome)rRNARibosomal – where the proteins are assembled.Reminder: Ribosomes are made up of protein and RNAtRNATransfers each amino acid to the ribosome
6 How is a copy made? Transcription RNA Polymerase Where does it start? “Transcribe” orwrite a codeOnly 1 strandis made!RNA PolymeraseSeparates DNA strands (at Hydrogen bonds) and acts as “Police” in creating the mRNAWhere does it start?There are “start sites” called PromotersJust like promoters for events let people know what is going on.
7 Introns Exons Codons “Extra” parts that are cut out of the final mRNA strand.Exons“Good” parts that are splicedtogether to make the final mRNAstrandCodons3 (consecutive) nucleotides longEach one specifies for one of 20 amino acids64 different codons
8 Special Codons:Start Codon: AUGStop Codons: UAA, UAG, UGA
10 Translation “Translates” from one language to another Creates a chain of amino acidsKnown as a protein.It is the process of translating codons (mRNA) by using anti-codons (tRNA) into the amino acids they code for (which makes proteins)Occurs at the RibosomesAnti-codons are complementary to codons
11 Translation Can you identify the following: 1. mRNA 2. Codon 3. Anti-Codon4. Amino Acid5. Protein
12 What is the big picture? DNA is the Master Plan mRNA is the Blueprint Remains safe in the nucleusmRNA is the BlueprintDisposable copyrRNA is the Building sitetRNA are the buildersWorkers that make the proteins (amino acid chains)DNA makes proteins and proteins express genes!
13 Mutations Changes in the letter sequence of the DNA Chromosomal Gene Whole chromosome has been changedChange in the number of chromosomes or their structure.GeneSingle gene change (one or more letters)Two typesPointFrameshift
14 Point MutationOne nucleotide changes – May change the Amino Acid it codes for (and it may not)
15 Frameshift Mutation Typically makes the entire protein not useable. DeletionRemoval of one or more NucleotidesInsertionAddition of a Nucleotide