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8.4 •SetTranscription up Cornell Notes on pg. 5 8.4 Transcription 2.1 Atoms, Ions, and Molecules •Topic: 8.4 Transcription 1. 2. •Essential Question: 1. What is the central dogma? 2. Why can an mRNA strand made during transcription, be thought of as a mirror image of the DNA strand from which it was made? What is the central dogma? Why can an mRNA strand made during transcription, be thought of as a mirror image of the DNA strand from which it was made? KEY CONCEPT Transcription converts a gene into a singlestranded RNA molecule. 8.4 Transcription On Your OWN: The Central Dogma P.4 Draw fig 8.10 (pg.239)- color code • Red • Blue • Green Make a double-bubble map comparing and contrasting DNA and RNA (239-240) 3.2 Cell Organelles REVIEW: rough endoplasmic reticulum Have bumps called ribosomes which link amino acids together to form proteins 8.4 Transcription Proteins are used for movement, eyesight, and digestion and practically everything else you do. 8.4 Transcription KEY CONCEPT Transcription converts a gene into a single-stranded RNA molecule. RNA DNA 8.4 Transcription Connect • Suppose you want to play skeeball at a arcade. The game only takes tokens, but you only have quarters. What do you do? – You exchange your quarters for tokens. • In a similar way, your cells cannot make proteins from DNA. • They must convert the DNA into RNA in order to make proteins • This process is known as transcription 8.4 Transcription RNA carries DNA’s instructions. • The central dogma states that information flows in one direction from DNA to RNA to proteins. 8.4 Transcription • The central dogma includes three processes. 1. Replication • Copies DNA replication 2.Transcription • • • Converts DNA into RNA RNA is a link between DNA and proteins “quarters tokens” transcription translation 3.Translation • Interprets an RNA message into a string of amino acids that will make up a protein 8.4 Transcription • Protein Synthesis: the process whereby biological cells generate new proteins. Includes DNA replication, transcription, and translation. 8.4 Transcription Location of Protein Synthesis • Prokaryotic cells: replication, transcription, and translation all occur in the cytoplasm (remember there is no nucleus), at approx the same time • In Eukaryotic cells, where DNA is located inside the nucleus, these processes are separated by location and times. – Replication and transcription occur in the nucleus – Translation occurs in the cytoplasm 8.4 Transcription • RNA differs from DNA in three major ways. RNA Ribose Sugar Uracil (U) Single-Stranded Please add a drawing to each side of your double-bubble map DNA Deoxyribose Sugar Thymine (T) Double-Stranded 8.4 Transcription • RNA is similar to DNA in a few ways – Both are a chain of nucleotides – Each is made of a sugar, a phosphate group, and a nitrogen containing base – Each has A, C, & G 8.4 Transcription Protein Synthesis Video • Transcription 2m50s 8.4 Transcription • Transcription copies specific genes from DNA to make a complementary strand of RNA. – Only a gene, NOT the entire DNA strand is transcribed 8.4 Transcription To transcribe is to make a copy of DNA into a complementary messenger RNA strand 8.4 Transcription Get out 3 Colors and MAKE A KEY on the top of your handout -DNA -RNA - Transcription Complex (RNA Polymerase) 8.4 Transcription 1. RNA polymerase and other proteins, (which we call a transcription complex) recognize the start of a gene and unwind a segment of it. transcription complex start site nucleotides 8.4 Transcription Why must the DNA strands unwind and separate before transcription can take place? – The bases must be exposed so that the DNA can be read transcription complex start site nucleotides 8.4 Transcription 2. RNA polymerase, using the DNA as a template, strings together a “complementary” strand of RNA • Uracil bonds with Adenine U=A (no Thymine) • The DNA helix winds again as the gene is transcribed. RNA DNA RNA polymerase moves along the DNA 8.4 Transcription How does the base sequence of the RNA transcript being formed compare with the sequence on the template strand? • It is complementary RNA DNA RNA polymerase moves along the DNA 8.4 Transcription Transcription Practice Transcribe this DNA strand into a mRNA strand *Remember: No Thymine. Instead use Uracil. A=U DNA AAA TAG GAT ATC GGA TAC AGT RNA UUU AUC CUA UAG CCU AUG UCA 8.4 Transcription 3. The RNA strand detaches from the DNA once the gene is transcribed. • The transcription complex falls apart • DNA re-zips RNA 8.4 Transcription Where will the RNA transcript go after it separates from the DNA in step 3? • It is processed and LEAVES the nucleus, heads to the cytoplasm RNA 8.4 Transcription • Transcription makes three types of RNA. – Messenger RNA (mRNA) which has been transcribed from the DNA, carries the message that will be translated to form a protein. – Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made. – Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome. make a Replication vs. Transcription Double 8.4Please Transcription Bubble (bottom of pg. 4) Pg. 242 in book • Transcription and replication are similar, but have different end results. Please create a double-bubble map comparing and contrasting the two processes. – Replication copies all of the DNA – Transcription copies a specific gene. one gene – Replication makes one copy (only happens once) – Transcription can make many copies (happens almost continuously) growing RNA strands DNA 8.4 Transcription Similarities between DNA replication and Transcription? • • • • • Occur within the nucleus Both are catalyzed by enzymes Both unwind DNA “complementary” base pairing Highly regulated (very carefully done- we want NO mistakes) Differences? • End results are different • Replication makes an identical copy of ALL of the DNA • Happens only once during the cell cycle • Transcription only makes a complementary strand of segments of DNA • Can happen over and over again at anytime 8.4 Transcription Practice DNA A T C G A A A T C G G G A T T RNA U A G C U U U A G C C C U A A