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Chapter 8 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Homework. Chapter 7. Chapter 8. P 151 Do the 3 Questions under intro on sickle cell anemia Concept Review #1, 2, 3,4,5,6,7,9,11. Concept Review
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Chapter 8 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Homework Chapter 7 Chapter 8 P 151 Do the 3 Questions under intro on sickle cell anemia Concept Review #1, 2, 3,4,5,6,7,9,11 • Concept Review • #1, 2, 3, 6, 8 Draw diagram that illustrates how photosynthesis and respiration are related
Review • What is transcription? • What is translation? • What are the DNA bases? • What are the RNA bases? • How do they pair up?
What were some of the organisms that you learned about in the first lab exercise yesterday? • What is a mutation? • What is a gene?
DNA and the Importance of Proteins • The recipes for proteins are found in the cell’s DNA. • DNA is organized into genes. • Each gene is a recipe for different proteins.
Nucleic Acid Structure and Function • DNA accomplishes two things: • Passes genetic information to the next generation • Controls the synthesis of proteins • DNA is able to accomplish these things because of its unique structure. • So, how do we know DNA’s structure?
Important Researchers in the Search for DNA’s structure • Frederick Griffith, Linus Pauling, Chargaff, Oswald Avery and associates, Alfred Hershey and Martha Chase
The race to determine the structure of DNA X-ray diffraction image of DNA taken by Rosalind Franklin in 1951 Maurice Wilkins Rosalind Franklin Photo 51 Wet DNA
Nobel Prize 1962: Watson, Crick, Wilkins What about Rosalind Franklin?
DNA Structure • DNA is a nucleic acid. • Nucleic acids • Large polymers made of nucleotides • A sugar molecule • Deoxyribose for DNA • A phosphate group • A nitrogenous base • Adenine • Guanine • Cytosine • Thymine
DNA Structure • DNA is double- stranded. • Held together by hydrogen bonds between the bases • A-T, G-C • Why do you think they pair this way?
Base Pairing Aids DNA Replication • DNA replication • Why does the cell need to replicate its DNA? • Is the process by which DNA is copied • This is done before cell division. • Provides the new cells with a copy of the genetic information • Relies on the base-pairing rules
Base Pairing Aids DNA Replication • Is accomplished by DNA polymerase and other enzymes • DNA Helicase binds to DNA and forms a replication bubble (or replication fork) by separating the two strands. • DNA polymerase builds new DNA strands that will pair with each old DNA strand. • Where there is an A on the old strand, polymerase will add a T to the new strand. • When DNA polymerase finishes a segment of new DNA, it checks its work and corrects mistakes if they happen.
DNA Replication Helicase: unzips DNA Polymerase: incorporates nucleotides into new strand
DNA replication • http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=related
Handout on DNA Replication • Complete the handout and questions; you may work together
Repairing Genetic Information • If a mistake is made when building the new strand • The old strand still has the correct information. • This information can be used to correct the new strand.
The DNA Code • The order of bases in the DNA molecules is the genetic information that codes for proteins. • The sequence of nucleotides forms words that are like a recipe for proteins. • Each word contains three base letters. • (base triplet) • ATGC are the four letters that are used to make the words. • Each three-letter word codes for a specific amino acid. • The order of amino acids in the protein is determined by the order of nucleotides in DNA.
RNA Structure and Function • RNA vs. DNA • RNA has ribose sugar (DNA has deoxyribose). • RNA contains the bases • Adenine • Guanine • Cytosine • Uracil (DNA has thymine)
DNA vs. RNA • RNA’s, like DNA’s, base sequence carries information. • RNA is made in the nucleus and transported to the cytoplasm (DNA stays in the nucleus). • The protein coding information in RNA comes from DNA. • Like DNA replication, RNA synthesis follows the base-pairing rules (A-U; G-C). • RNA is typically single-stranded (DNA is typically double-stranded). • Three types of RNA participate in protein synthesis • mRNA • tRNA • rRNA
Protein Synthesis • The sequence of nucleotides in a gene dictates the order of amino acids in a protein. • Before a protein can be made • The information in DNA must be copied into RNA. • This process is called transcription. • The information in the RNA can then be used to make the protein. • This process is called translation.
Transcription animation • http://www.youtube.com/watch?v=ztPkv7wc3yU
Transcription • During transcription • DNA is used as a template to make RNA • Accomplished by RNA polymerase and follows the base-pairing rules • The process of transcription • Occurs in the nucleus • RNA polymerase separates the two strands of DNA. • Only one of the two strands will be used to create the RNA. • The coding strand • The other DNA strand is called the non-coding strand.
The Process of Transcription • Only a segment of the DNA strand will be used to create each RNA. • These segments are called genes. • Each gene starts with a promoter. • The RNA polymerase binds to the promoter to start building an RNA strand. • Each gene ends with a terminator sequence. • The RNA polymerase will stop transcribing at the terminator sequence.
Translation animations • http://www.youtube.com/watch?v=B6O6uRb1D38&feature=related • http://www.youtube.com/watch?v=5bLEDd-PSTQ&feature=related
Translation • Three types of RNA participate in translation. • mRNA carries the recipe for making the protein. • tRNA and rRNA are used to read the recipe and build the amino acid chain. • Codons are sets of three nucleotides on mRNA that code for specific amino acids. • tRNA reads the codons and brings the correct amino acids.
Translation • Ribosomes are organelles that build proteins. • rRNA is found in ribosomes. • mRNA is read on ribosomes. • Ribosomes are found in two places in the cell. • Free-floating in the cytoplasm • Bound to the endoplasmic reticulum
Translation Initiation • Translation begins when • The small ribosomal subunit binds to the beginning of the mRNA and searches for the AUG start codon. • At this point, a tRNA brings the first amino acid. • The anticodon in the tRNA matches with a codon on the mRNA. • Each tRNA carries a specific amino acid based on its anticodon. • The start codon, AUG, binds to a tRNA that carries a methionine. • Finally, the large ribosomal subunit joins the complex and the next step, translation elongation, can proceed.
Translation Elongation • The next tRNA binds with the next codon on the mRNA. • The ribosome adds this amino acid to the growing polypeptide. • The ribosome then moves down to the next codon. • The process repeats itself. For each step, a new amino acid is added to the growing protein.
Translation Termination • Elongation continues until the ribosome encounters a stop codon. • UAA, UAG, UGA are stop codons. • A release factor binds to the stop codon. • This causes the ribosome to release the polypeptide. • The ribosomal subunits separate and release the mRNA. • The mRNA can be translated again by another ribosome.
The Genetic Code is Nearly Universal • The process of making proteins from the information in DNA is used by nearly all cells. • Nearly all organisms studied to date use the same genetic code. • Because of this, we are able to use bacteria as factories to make massive amounts of proteins. • Insulin, growth factor, etc.
Control of Protein Synthesis • Gene expression is how the cell makes a protein from the information in a gene. • Cell types are different from one another because they express different sets of genes. • Therefore, have different sets of proteins • Cells control gene expression in response to different environmental conditions. • Cells can alter gene expression • Controls the quantity of a protein • Controls the amino acid sequence of a protein
Control of Protein Quantity • Cells can regulate how much of a given protein is made by • Controlling how much mRNA is available for translation • Cells do this in a number of ways: • Regulating how tightly the chromatin is coiled in a certain region • The more tightly the chromatin is coiled, the less likely a gene in that region will be transcribed.
Control of Protein Quantity • By increasing or decreasing the rate of transcription of the gene by enhancer and silencer regions on the DNA • Activation of enhancer regions increases transcription. • Activation of silencer regions decreases transcription. • Through the binding of transcription factors, • These proteins bind to the promoter and facilitate RNA polymerase binding and transcription. • By limiting the amount of time the mRNA exists in the cytoplasm, • Some mRNA molecules are more stable and will exist longer in the cytoplasm, yielding more protein.
Different Proteins from One Gene • Eukaryotic cells can use one gene to make more than one protein. • In eukaryotic genes, non-coding sequences called introns, are scattered throughout the sequence. • After transcription, the introns must be cut out and the coding regions, called exons, must be put back together. • This is called splicing.
Alternative Splicing • Different combinations of exons from a single gene can be joined to build a number of different mRNAs for a number of different proteins.
