Unit 4 Protein Synthesis Notes PDF

Unit 4 Notes Protein Synthesis PLEASE NOTE THAT THIS PRESENTATION IS DIVIDED INTO SECTIONS. ALL SECTIONS ARE NEEDED TO FULLY COMPLETE YOUR NOTES DUE ON THURSDAY, 10/17.  Part 1: DNA vs. RNA *Your notes outline is...

Unit 4 Notes Protein Synthesis PLEASE NOTE THAT THIS PRESENTATION IS DIVIDED INTO SECTIONS. ALL SECTIONS ARE NEEDED TO FULLY COMPLETE YOUR NOTES DUE ON THURSDAY, 10/17.  Part 1: DNA vs. RNA *Your notes outline is a summary of big ideas. If you are unable to distinguish between the 3 types of RNA or any of this information is new to you, you should include it in your notes.  DNA Review Double Helix Monomer: Nucleotides ○ Deoxyribose Sugar ○ Nitrogenous Bases: Adenine, Thymine, Cytosine, Guanine ○ Phosphate Group  DNA Review Where is DNA found? The Nucleus because DNA is TOO BIG to leave the nucleus What does DNA code for? Genes that make proteins. BUT the protein factory (ribosome) is in the cytoplasm, NOT in the nucleus. Since DNA can’t leave the nucleus, we need a little helper: RNA.  Ribonucleic Acid RNA – acts as a messenger between DNA and ribosomes, and carries out the process by which proteins are made from amino acids.  4 Differences Between RNA 1. Sugar: and DNA ○ RNA – ribose ○ DNA – deoxyribose 2. Number of Strands: ○ RNA – single strand of nucleotides ○ DNA – double strand of nucleotides 3. Where are they found? ○ RNA found – inside and outside nucleus ○ DNA found – inside nucleus only – TOO BIG TO LEAVE!  4 Differences Between RNA and DNA 4. Base Pairing: RNA has uracil instead of – thymine ○ RNA cytosine (C) pairs with DNA – guanine (G) ○ RNA guanine (G) pairs with DNA – cytosine (C) ○ RNA adenine (A) pairs with DNA – thymine (T) ○ RNA uracil (U) pairs with DNA – adenine (A) DN RN A A  3 types of RNA 1. mRNA (messenger RNA) 2. tRNA (transfer RNA) 3. rRNA (ribosomal RNA)  3 Types of RNA: mRNA Messenger RNA (mRNA): copies the code from DNA in the nucleus and takes the code to the ribosome (factory)  3 Types of RNA: tRNA Transfer RNA (tRNA): transfers (or carries) one amino acid to the ribosome to match up with the mRNA and build a protein.  3 Types of RNA: rRNA Ribosomal RNA (rRNA): along with proteins, makes up the ribosomes Part 2a: Gene Expression  RECALL: Chromosomes are divided into segments called genes Basic unit of heredity that occupies a specific location on the chromosome. Most genes code for directions for building all the proteins needed by an organism  Gene Expression When the product of a gene (a specific protein) is being actively produced by a cell. Not all genes are active (expressed; gene is turned on) at the same time: some genes are rarely expressed – adrenaline some genes are constantly expressed – hair growth, blood pressure some genes are expressed for a time, then turned off (cyclical) – estrogen  Protein Synthesis A TWO stage process where DNA is used to produce proteins which code for traits. Also called Gene Expression (Central Dogma) Central Dogma  Why is it important that gene expression be regulated? Because the cell would produce many molecules that it does NOT need – waste of energy and raw materials Different kinds of cells require different kinds of molecules to function Cell Differentiation: All of your cells have specific functions ex: RBC’s need hemoglobin to bind O2, but other cells do not  RECALL: Where do amino acids come from in our body? Proteins are composed of amino acids – there are 20 different amino acids Different proteins are made by combining these 20 amino acids in different combinations (only 11 our body can produce naturally)  Two Steps of Protein Synthesis (Gene expression) Transcription: Transferring information from DNA to mRNA so it can leave the nucleus and travel to the ribosome. Translation: tRNA decodes the message from mRNA by carrying amino acids to make a protein at the ribosome.  Part 2b: Transcription  Transcription Purpose: Transfer information from DNA to mRNA Why do we have to do transcription?? DNA has code for protein that needs to be made Proteins are made in the ribosomes DNA is too large to leave the nucleus (double strand) RNA can leave the nucleus (single strand)  Enzyme RNA polymerase RNA Polymerase binds to DNA, unzips it and uses one strand of DNA as a template to build a single stranded mRNA (messenger RNA)  Regulation Before mRNA passes out of the nucleus to enter the cytoplasm, it is processed/edited because we need to remove non-coding regions of DNA. ○ Introns – Non-coding segments– are removed ○ Exons – expressed, code for amino acids, joined together  Regulation 1. Both introns and exons are transcribed by mRNA, but introns do not leave the nucleus ○ Introns may be old DNA no longer used, or may regulate gene expression 2. Before mRNA leaves the nucleus, introns are cut out so just the code for protein production leaves. Then exons are spliced together to form final mRNA that leaves nucleus.  So what next?? After transcription mRNA needs to leave the nucleus and go to the ribosome so translation can happen.  Part 2c: Translation Translation: mRNA→ Protein  Translation: mRNA→ Purpose: Protein Decodes mRNA into a protein tRNA (transfer RNA) carries amino acids to the ribosome and decodes mRNA 3 bases at a time. Amino acids are joined together to make a protein.  What is a codon? A series of three mRNA bases that code for a specific amino acid. Start Codon: AUG (codes for methionine) Stop Codons: UAG, UAA, UGA  How to read a codon Codons correspond to a chart: specific amino acid. Use a codon chart to figure out which amino acid.  How does tRNA help with translation? -tRNA has a triplet of nucleotides Amino acid (Alanine) that is complementary to the codon in mRNA – called an anticodon -tRNA matches the appropriate amino acid -rRNA- part of the ribosome; binds Anticodon with mRNA and tRNA to help read G-C-C mRNA the order of amino acids and link them together  Steps of Translation 1. Initiation- the ribosome assembles around the mRNA; the 1st tRNA is attached at the START codon 2. Elongation- the tRNA transfers an amino acid to the tRNA of the next codon 3. Termination- when the STOP codon is reached, the ribosome releases the polypeptide 1.  Translation Steps Amino acids are joined together to make a protein/polypeptide. 2. 3.  Review: Translation Steps 1. mRNA leaves nucleus and binds to ribosome 2. tRNA with anticodon UAC and amino acid Methionine binds to start codon. 3. Next tRNA comes to ribosome 4. Enzyme joins two A.A.s – creating a peptide bond 5. 1st tRNA leaves 6. 2nd tRNA slides over bringing the mRNA and AA chain along 7. Next codon in ribosome is ready for new tRNA anticodon (Process continues…until STOP codon) 8. When the protein is complete, the ribosome complex falls apart releasing new protein. Protein Synthesis Review DNA → RNA → PROTEIN→ TRAIT Part 3: Gene Mutations  Gene Mutations Gene Mutations are errors made when DNA is copied during replication– produces a change in a single gene ○ Rare occurrence: 1 in every 100,000,000 bases Errors can have a major effect on the protein being made: UGU codes for cysteine Error: UGA codes for the stop codon  Gene Mutations Point Mutation: occurs at a single point (change to ONE base) There are 3 different “types” of point mutations: Substitution, Deletion, and Insertion. Each of these changes will have a different effect on the protein being made.  Types of Point Mutations Substitution – one base (one nucleotide) is changed for another The effects of substitution can be silent, missense, or nonsense. Silent: the errors do NOT affect the protein being made. Ex. UGU codes for amino acid cysteine Error: UGC – still codes for cysteine Missense: the error affects ONE amino acid in the protein chain, which could have a range of effects on the protein as a whole, but will have some impact. Ex. See picture to the left Nonsense: the error causes an early STOP to be reached. This terminates the polypeptide chain sequence early and does not allow for the entire protein to be formed. This will severely affect the protein being made. Ex. DNA: ACG 🡪 ACA  Types of Point Mutations Deletion or Insertion – base removed or inserted from the DNA sequence→ these both will cause a frameshift Frameshift mutation – shifts the reading frame of genetic message frame shift mutation may change every amino acid that follows the point of mutation this can make the protein unable to function  Causes of Gene Mutations 1. Can occur spontaneously in the cell 2. Environmental agents (mutagenic agent--causes mutations through disrupting replication) → (examples: UV light, radiation) 3. Cancer causing agents – carcinogens ○ examples: chemicals (cigarette smoke), viruses (HPV)