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October 27, 2009 • Write down objectives and activities! • Record your test grade (MAJOR) on your new gradesheet for the 2nd nine weeks!! • Review power standards for Photosynthesis, Cellular Respiration and DNA… Protein Synthesis *Gene Expression* After replication… TRANSCRIPTION and TRANSLATION Transcription and Translation DNA RNA (Transcription) RNA Protein (Translation) Where do replication and transcription take place? Why? RNA – The “Other” Nucleic Acid Differs from DNA : 1. RNA is a single strand of nucleotides DNA is a double strand of nucleotides (helix) 2. Ribose is sugar Deoxyribose is sugar in DNA 3. No Thymine, Uracil (U) replaces Thymine Three Forms: •Messenger RNA (mRNA) •Ribosomal RNA (rRNA) •Transfer RNA (tRNA) Key Players: mRNA – messenger RNA Leaves nucleus with instructions! tRNA – transfer RNA Ribosome - rRNA Transcription **Occurs in the nucleus 1. Different enzyme binds to the start signal on DNA 2. Unwinds and separates DNA 3. One side of DNA is used as the template to make the copy of RNA 4. RNA Nucleotides bind with complementary bases (U pairs with A) 5. Complete when enzyme reaches the stop code T T A T G C A T C G What will be the complimentary RNA sequence? New RNA dangles off the enzyme DNA closes back to a double helix shape Working copy of RNA is edited Introns – Noncoding (intervening) sequences– edited out Exons – Code for amino acids – (exit nucleus) spliced together Example: ACAAUGGACAGU is the RNA code If the code for the protein is ACUGGU, what are the introns/exons? Three Types of RNA Made in Transcription mRNA – Blueprint for protein synthesis travels from nucleus to ribosome tRNA – Translates mRNA code to amino acids (monomers of protein!) rRNA – Makes up ribosomes October 29, 2009 • • 1. 2. 3. 4. 5. 6. 7. 8. Write down your objectives and activities! Turn in your “Challenge Questions” if you finished it…if not, get a ZAP pass NOW! Warm Up: (Write the questions!!!) What are the 3 differences between DNA and RNA? Is this DNA or RNA? – TATTAGCTAG Is this DNA or RNA? – AUAAUCGAUC What two processes occur in the nucleus? What is the end result of replication? What is the end result of transcription? What is the end result of translation? What is the end result of protein synthesis? The Genetic Code Instructions for building a protein come from: Codon – 3 base code on mRNA – codes for amino acids or is a stop signal Genetic code is nearly universal for all organisms!! Codons 20 Different kinds of amino acids Sequence of three bases gives enough different combinations to code for all of them = CODONS! 64 possible codons – 61 code for amino acids 3 are stop signals Each codon codes for one AA, but there is more than one codon for most AA. The Genetic Code November 2, 2009 • Write down objectives and activities. • Turn in homework. • Get a ZAP pass if you don’t have it! Warm Up: 1. What is the end result of replication? 2. What is transcription? 3. What is translation? 4. Where are codons located? 5. Where are anticodons located? 6. What kind of RNA is used in transcription? 7. What kind of RNA is used in translation? Remember the Key Players… mRNA tRNA ribosome Translation *Occurs in cytoplasm on ribosomes! *Strings Amino Acids together to form protein that will express a gene! tRNA RNA folded with three loops One loop has three nucleotide sequence (Anticodon) which is complementary to mRNA codon For example, if codon is CAA anticodon would be GUU… “End” of tRNA carries AA that corresponds with the mRNA codon (remember: codon comes from wheel/chart!) No anticodon for codons UAG, UAA, OR UGA (Stop Codons) Translation 1. mRNA leaves nucleus & binds to ribosome 2. tRNA with anticodon UAC and AA Methionine binds to start codon 3. Next tRNA comes to ribosome 4. Enzyme joins two AA Ribosome mRNA tRNA 5. 1ST tRNA leaves Amino Acid Chain 6. 2ND tRNA slides over bringing the mRNA and AA chain along tRNA tRNA anticodon mRNA codon 7. Next codon in ribosome is ready for new tRNA anticodon (Process continues…) 8. Continues until stop codon Finally, Step 9…. Ribosome complex falls apart releasing new protein!!! Concept Map Section 12-3 RNA can be Messenger RNA also called Ribosomal RNA which functions to mRNA Carry instructions also called which functions to rRNA Combine with proteins from to to make up DNA Ribosome Ribosomes Transfer RNA also called which functions to tRNA Bring amino acids to ribosome