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Unit 3.1 – Protein Synthesis DAY 1 Journal Questions A question given to you every few days To be checked on Tuesdays during Eagle time Mrs. Nedrow and Mrs. Mahan’s class go to other Bio teacher Turn all 6 in with test Receive 6 extra credit points (1/q) Warm Up INDIVIDUALLY: Create a thinking map to compare and contrast DNA to RNA. Where in the cell is it? What is it made of? Nitrogen Bases? Types Warm Up In small groups: Compare your thinking maps Make changes to yours if you need to RNA vs. DNA DNA Double stranded Deoxyribose sugar Bases: C,G A,T RNA Single stranded Ribose sugar Bases: C,G,A,U Both contain a sugar, phosphate, and base. Protein Structure Made up of amino acids Polypeptide- string of amino acids 20 amino acids are arranged in different orders to make a variety of proteins Assembled on a Ribosome Questions to be answered today How do we get from the base sequences found in DNA to a bunch of amino acids? How do we get from a bunch of amino acids to proteins? Replication •DNA double helix unwinds •DNA now single-stranded •New DNA strand forms using complementary base pairing (A-T, C-G) •Used to prepare DNA for cell division •Whole genome copied/replicated DNA makes new DNA Transcription and Translation: An Overview (aka the Central Dogma) DNA Transcription RNA Translation Protein Transcription and Translation Cells are governed by a cellular chain of command We call this the “Central Dogma” Transcription DNA RNA protein traits Is the synthesis of RNA under the direction of DNA Produces messenger RNA (mRNA) Translation Is the actual synthesis of a polypeptide, which occurs under the direction of mRNA Occurs on ribosomes We’ll start discussing this process tomorrow. Closing Write a short paragraph comparing DNA to RNA - types, locations, structure, etc. COMPLETE SENTENCES! DAY 2 Warm Up What type of RNA copies DNA? mRNA What is this process called? Transcription Transcription RNA forms base pairs with DNA C-G A-U (NOT T) Primary transcriptlength of RNA that results from the process of transcription TRANSCRIPTION ACGATACCCTGACGAGCGTTAGCTATCG UGCUAUGGGACU Major players in transcription Messenger RNA mRNA- type of RNA that encodes information for the synthesis of proteins and carries it to a ribosome from the nucleus Major players in transcription RNA polymerase 2 functions: Unwind DNA sequence strings together the chain of RNA nucleotides Does what both Helicase and DNA Polymerase did in DNA Replication mRNA Processing Primary transcript is not mature mRNA DNA sequence has coding regions (exons) and non-coding regions (introns) Introns must be removed before primary transcript is useful mRNA and can leave nucleus Let’s Practice! Closing Write a “journal response” using the Transcription vs. Translation Handout as a guide…ONLY FILL IN TRANSCRIPTION: Purpose Process Location in cell End product DAY 3 Warm Up Separate this DNA sequence into codons Transcribe this sequence & Splice out UAA ATTGCGATGTCGGCTGACCCC ATT GCG ATG TCG GCT GAC CCC UAA CGC UAC AGC CGA CUG GGG UAA CGC UAV AGC CGA CUG GGG What is this process called and why is it important? Gene splicing, to control gene expression Transcription is done…what now? Now we have mature mRNA transcribed from the cell’s DNA. It is leaving the nucleus through a nuclear pore. Once in the cytoplasm, it finds a ribosome so that translation can begin. We know how mRNA is made, but how do we “read” the code? Translation Second stage of protein production Translation Translation is the RNA-directed synthesis of a polypeptide Translation involves: mRNA Ribosomes - Ribosomal RNA Transfer RNA Genetic coding - codons Step 1 Translation from mRNA to Protein • As translation begins, one end of mRNA strand coming from the nucleus attaches to a ribosome. mRNA strand Ribosome Reading the DNA code Every 3 DNA bases pairs with 3 mRNA bases Every group of 3 mRNA bases encodes a single amino acid Codon- coding triplet of mRNA bases How many bases code for each amino acid? 3 bases = 1 codon 1 codon = 1 amino acid 3 bases = 1 amino acid Step 2 Translation from mRNA to Protein • tRNAs bring amino acids to the ribosomes. mRNA Coming from Nucleus RIBOSOME Amino acid Each tRNA only carries one amino acid. Transfer RNA Bound to one amino acid on one end Anticodon on the other end that complements the mRNA codon • There are also three nucleotides on the bottom of the tRNA called an anti-codon. • Anti-codons complementary base pair with the codons on mRNA. (this is to make sure they are bringing the correct amino acidIf the anti-codon doesn’t base pair with the codon, then the wrong amino acid was brought) Anti-codon • AUG is the first codon on the mRNA strand. • This signals the ribosome to START making a protein Methionine • A tRNA with anticodon UAC comes and binds with this codon and drops off it’s amino acid “Methionine”. Step 3 • After the first tRNA binds with its codon, the mRNA slides down so that the ribosome can read the next codon. Step 4 • A new tRNA molecule carrying an amino acid pairs with the second mRNA codon. Alanine Step 5 • The amino acids then bond together. • Once the first tRNA lets go of it’s amino acid, it is released from the ribosome. Methionine Alanine bond • A chain of amino acids is formed until the stop codon is reached on the mRNA strand. The end result is a protein Stop codon Transcription vs. Translation Review Transcription Process by which genetic information encoded in DNA is copied onto messenger RNA Occurs in the nucleus DNA mRNA Translation Process by which information encoded in mRNA is used to assemble a protein at a ribosome Occurs on a Ribosome mRNA protein PRACTICE!!! Closing Write a “journal response” using the Transcription vs. Translation Handout as a guide…FILL IN TRANSCRIPTION & TRANSLATION: Purpose Process Location in cell End product DAY 4 Warm Up Translate the following mRNA strand into an amino acid strand using the codon chart. AUGCACUGUCCUUUCGCUGAC The Genetic Code Genetic information is encoded as a sequence of nonoverlapping base triplets, or codons So now we get to the codon table! Locate the first letter of your codon using the left side of the table. Ex. AUG Look for the A Now move to the second letter of your codon which is ‘U’ Look across the top of the table Find the letter ‘U’ and follow it down until it intersects with the letter ‘A’ from the left side(1st letter). You should see four amino acids (isoleucine, isoleucine, isoleucine, and (start) methionine. Codon: AUG Down to the last letter of the codon! Look to the right hand side for the third letter. Find the letter ‘G’ which will intersect with the box that had the four choices. Trace from the ‘G’ on the left over to the left and you should land on ….. Methionine (start) Yes you did it!!! Now try another codon Codon: AUG Try the codon CAC Did you get the amino acid ‘histidine’? What do these codons have to do with proteins? Each codon represents an amino acid that will eventually form a protein that is used within a cell. Proteins are made up of hundreds of amino acids in a specific sequence. When they get “out of order’ a mutation occurs. Long string of amino acids will form ACGATACCCTGACGAGCGTTAGCTATCG UGCUAUGGGACUGCU Let’s Practice… DAY 5 Warm Up What is a mutation? Any changes that take place in DNA Explain how a mutation can be a benefit to an organism. The classic example of evolutionary change in humans is the hemoglobin mutation that makes red blood cells take on a curved, sickle-like shape. With one copy, it resists malaria, but with two copies, it causes the illness of sickle-cell anemia. Mutations • Any change in DNA sequence is called a mutation. • Mutations can be caused by errors during replication, transcription, translation, or cellular division. Types of Mutations you need to know: Point Mutations Frameshift Mutations Insertion Deletion Some mutations are inherited from parents • Mutations on sex cells (gametes) - passed on to offspring. • If a sperm or egg cell has a mutation and is fertilized, the altered gene would become part of the genetic makeup of the offspring. Every cell in that person would contain the mutation. • Sometimes a mutation can have no effect at all. For instance, if a codon sequence was suppose to be AUU Why would it have no effect on the person if a mutation caused the codon sequence to be AUC Some mutations occur “randomly” in BODY CELLS (any cell that is not a sex cell) • What happens if powerful radiation hits the DNA of a body cell, such as in skin, muscle, or bone? Will that affect this person’s offspring? • If a body cell’s DNA is changed, this mutation would not be passed on to offspring. Types of Mutations • A point mutation is a change in a single base pair in DNA. THE DOG BIT THE CAT. THE DOG BIT THE CAR. • Does this one letter change the meaning of the entire sentence? • Result: A change in a single nitrogenous base can change the structure of a protein causing it to not function properly. Because one base was changed from a G to an A, it caused the wrong amino acid to be put in the protein. mRNA Normal Protein Stop Replace G with A mRNA Point mutation Protein Stop It is called a point mutation, because it happens at one point. Types of Mutations • A mutation in which a single base is added or deleted from DNA is called a frameshift mutation because all the codons shift from one base. • Also may be called: deletion mutation or insertion mutation Deletion of U Types of Mutations Result: • Instead of just one amino acid being wrong, this changes ALL the amino acids after the mutation. • This causes much bigger problems than a point mutation. Deletion of U Causes of Mutations • Many mutations are caused by factors in the environment, such as radiation, chemicals, and even high temperatures. • Any external agent that can cause a change in DNA is called a mutagen. Repairing DNA • Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. • These repair mechanisms work extremely well, but they are not perfect. • The greater the exposure to a mutagen (such as UV light), the more likely that a mistake will not be corrected. Cowabunga!!!