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1. DNA, RNA structure 2. Transcription, translation DNA is a double-stranded helix • James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin Figure 10.3A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA and RNA are polymers of nucleotides • DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Sugar Phosphate group Nitrogenous base (A, G, C, or T) Nucleotide Thymine (T) Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.2A • DNA has four kinds of bases, – Adenine(A), Thymine (T), Cytosine (C), and Guanine (G) Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Figure 10.2B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Each strand of the double helix is oriented in the opposite direction 5 end 3 end P P P P P – Anit-Parellel: means parellel but moving in different directions P P P Figure 10.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3 end 5 end • RNA is also a nucleic acid – different sugar (ribose) – Uracil instead of Thymine – Still has Adenine, Guanine, Cytosine – Single strand, usually Nitrogenous base (A, G, C, or U) Phosphate group Uracil (U) Sugar (ribose) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.2C, D Types of RNA Genetic information copied from DNA is transferred to 3 types of RNA: __________ RNA: mRNA Copy of information in DNA that is brought to the ribosome and translated into protein by tRNA & rRNA. __________ RNA: rRNA Most of the RNA in cells is associated with structures known as ribosomes, the protein factories of the cells. It is the site of translation where genetic information brought by mRNA is translated into actual proteins. ___________ RNA: tRNA Brings the amino acid to the ribosome that mRNA coded for. Copyright © 2003 Pearson Education, Inc. on publishing as Benjamin Cummings From the Virtual Cell Biology Classroom ScienceProfOnline.com Images: Blueprint, clipart; Factory, Andreas Praefcke; Truck, PRA. • The information constituting an organism’s genotype is carried in its sequence of bases – The DNA is transcribed into RNA, which is translated into a chain of amino acids – Bases of Central Dogma DNA TRANSCRIPTION RNA TRANSLATION Protein Figure 10.6A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Transcription produces mRNA RNA polymerase RNA nucleotide Direction of transcription Template strand of DNA Figure 10.9A Newly made RNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA polymerase • In transcription, DNA helix unzips DNA of gene Promoter DNA – RNA nucleotides line up along one strand of DNA, following the base-pairing rules – single-stranded messenger RNA peels away and DNA strands rejoin Initiation Elongation Terminator DNA Area shown in Figure 10.9A Termination Growing RNA Completed RNA Figure 10.9B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA polymerase RNA transcripts of DNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Translation of mRNA into amino acids • The “words” of the DNA “language” are triplets of bases called codons – The codons in a gene specify the amino acid sequence of a protein – In other words, codons are every 3 bases. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Protein Figure 10.7 Amino acid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • An exercise in translating the genetic code Transcribed strand DNA Transcription RNA Start codon Polypeptide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Translation Stop codon Figure 10.8B Transfer RNA molecules serve as interpreters during translation • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a protein • The process is aided by transfer RNAs Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Figure 10.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Each tRNA molecule has a triplet anti-codon on one end and an amino acid attachment site on the other Amino acid attachment site Anticodon Figure 10.11B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes build chains of amino acids Next amino acid to be added to protein Growing protein tRNA molecules P site A site Growing protein Large subunit tRNA P A mRNA mRNA binding site Codons mRNA Small subunit Figure 10.12A-C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An initiation codon marks the start of an mRNA message AUG = methionine Start of genetic message End Figure 10.13A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • mRNA, a specific tRNA, and the ribosome subunits assemble during initiation Large ribosomal subunit Initiator tRNA P site A site Start codon mRNA Small ribosomal subunit 1 Figure 10.13B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 How does translation happen? • The mRNA moves one codon at a time relative to the ribosome – A tRNA pairs with each codon, adding an amino acid to the growing protein – A STOP codon causes the mRNA-ribosome complex to fall apart – This results in a chain of amino acids • Amino Acid (AA) + AA + AA + AA…etc = Protein Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Transcription RNA RNA polymerase DNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Translation Lysin e mRN A tRNA Translation direction Ribosome Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pause for Worksheet COMPLETE -PROTEIN SYNTHESIS WORKSHEET -BOOK WORKSHEET Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings b a Red object = ? What molecules are present in this photo? Table 14.2 Types of RNA Type of RNA Functions in Messenger RNA (mRNA) Nucleus, migrates to ribosomes in cytoplasm Transfer RNA (tRNA) Cytoplasm Provides linkage between mRNA and amino acids; transfers amino acids to ribosomes Ribosomal RNA (rRNA) Cytoplasm Structural component of ribosomes Function Carries DNA sequence information to ribosomes Review: The flow of genetic information in the cell is DNARNAprotein • The sequence of codons in DNA spells out the primary structure of a protein – A chain of amino acids form proteins that cells and organisms use Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Overview Eukaryotic Cell ______________ Synthesis of RNA under the direction of DNA (mRNA). ______________ Actual synthesis of a polypeptide (protein) under the direction of mRNA. Copyright © 2003 Pearson Education, Inc. on publishing as Benjamin Cummings From the Virtual Cell Biology Classroom ScienceProfOnline.com Diagram: Transcription & Translation, NIH Pause for Worksheet COMPLETE -DNA MOLECULE & REPLICATION Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings So how is DNA read to make Amino acids • We use the Genetic Coding Chart • Virtually all organisms share the same genetic codethe sequence is what is important Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings This is another one Second Base C U UUU UUC UUA UUG C CUU CUC CUA CUG A AUU AUC ile AUA AUG met (start) ACU ACC ACA ACG G GUU GUC GUA GUG GCU GCC GCA GCG phe leu leu val UCU UCC UCA UCG CCU CCC CCA CCG A ser UAU UAC UAA UAG pro CAU CAC CAA CAG thr AAU AAC AAA AAG ala GAU GAC GAA GAG Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings G tyr stop stop his gln asn lys asp glu UGU UGC UGA UGG CGU CGC CGA CGG AGU AGC AGA AGG GGU GGC GGA GGG cys stop trp arg ser arg gly U C A G U C A G U C A G U C A G Third Base First Base U Before we begin • In DNA – A binds with T (like AT&T) – C binds with G (like Cover Girl) – RNA is the same BUT there is no T • It is a U so A and U bind together Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 1: • Create a DNA sequence with 30 bases – Must start with TAC – Must end with ATT – After that you are good to go with any bases Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 2: • Using your DNA, make a complimentary mRNA strand Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 3: • Using your mRNA strand – Start at the beginning and circle every 3 codons Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 4: • Look at your first codon – Match the first letter, second letter and third letter to the Genetic Coding Chart. – Write the Amino Acid under the circled codon Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Step 5: • Continue until all codons are labeled with an amino acid • Now you have a chain of Amino Acids – Also called a PROTEIN Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Example DNA strand A–T–G–C–C–T–T–T–G T–A–C–G–G–A–A–A–C – mRNA strand A – U – G – C – C – U – U – U – G 1st codon A-U-G amino acid = methionine 2nd codon C-C-U amino acid = proline 3rd codon U-U-G amino acid = leucine methionine proline Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings leucine Pause for Worksheet COMPLETE THE 3 GENETIC CODING WORKSHEETS Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Confused? Here are links to fun resources that further explain genetic transcription & translation: • Molecular Genetics: Transcription & Translation Main Page on the Virtual Cell Biology Classroom of Science Prof Online. • “That Spells DNA” song by Jonathan Coulton. • DNA Transcription • Transcribe & Translate a Gene, from • DNA Transcription and Protein Assembly • Genetic by Sonic Youth. • Transcription and Translation animated movie • “The Protein Synthesis Song” by Kyrk. step-through animation by John University of Utah. animated movie by RedAndBrownPaperBag. from PBS production “DNA: The Secret of Life. MrsPurpleMonster18. (You must be in PPT slideshow view to click on links.) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings From the Virtual Cell Biology Classroom on ScienceProfOnline.com