Unit 6 - Nucleic Acids The Genetic Code Transcription,...

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1 Nucleic Acids The Genetic Code Chem 004 - Spring 2007 Transcription, Translation and Replication Blackboard: http://blackboard.gwu.edu Office Hours: MW 3:10 – 3:55 PM, 1957 E street, room 213 or by appointment Deoxyribonucleic acid (DNA) - Mainly found in the cell nucleus - Very large molecules - Double stranded - Store genetic information Ribonucleic acid (RNA) - Found in the nucleus and in the cytoplasm of a cell - Large molecules, but small compared to DNA - Single stranded - Involved in protein synthesis P O - O O - O - Phosphate Chemical units of DNA Chemical units of DNA In RNA, deoxyribose is replaced by ________, O H H O O O H O H and Thymine by __________ H N N H O O O H H O O O H Sugar Deoxyribose N N N H N H 2 N CH 3 H N N H O O N N H N H 2 O H 2 N H N N N H N O Base Adenine Thymine Cytosine Guanine AC TG N N N N N H 2 O O H O P -O O - O O O O H N N O O N H N N O N H 2 N O O O P O -O O N N N H 2 O O O P O -O O O O H H N N O O P O -O -O P O DNA segment Thymine Cytosine Guanine Thymine
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2 Simplified representation of a single strand of DNA/RNA sugar P sugar P sugar P sugar P sugar P sugar P A G T C A G The Base compositions of DNA of Various Species 21.6 21.0 29.0 28.4 Bacillus subtilis (bacterium) 25.6 25.5 24.3 24.6 Escherichia coli (bacterium) 24.6 24.5 25.3 25.6 Zea mays (corn) 26.6 27.1 23.3 23.0 Neurospora crasa (mold) 22.5 22.5 27.6 27.3 Drosophila melanogaster (fruit fly) 18.4 19.1 31.5 31.0 Homo sapiens (human) Cytosine Guanine Thymine Adenine Species Chargaff’s rules: In every species, N N N H N N H H Adenine H 3 C N H H N O O Thymine N N H N O H H Cytosine N H N N N H N O H H Guanine Base pairing S S S S S S P P P P P P S S S S S S P P P P P P C T G A A G T C T C A G
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3 DNA is packaged into structures called chromosomes A G C C C C G G G A A A A T T T T T T G C T T C G G T C C T G A A A A A Replication (in the cell nucleus) Double strand of DNA How is the genetic information stored in DNA transferred to proteins? DNA RNA RNA molecules are produced The base sequence is translated to an amino acid sequence Protein
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4 The genetic code is written in groupings of three DNA bases called codons This information is transferred to an mRNA molecule during the transcription process. Each group of three bases (triplet) codifies for one amino acid. There are 64 possible codons and only 20 amino acids. There is redundancy in the code. Alanine Threonine Glutamine Leucine Arginine Serine Termination Transcription (in the cell nucleus) A G C C C C G G G A A A A T T T T T T G C T T C G G T C C T G A A A A A DNA strand A G C C C C G G G A A A A T T T T T T G C T T C G G T C C T G A A A A A C A A A A G G G C C C U U U U A G U mRNA Transcription (in the cell nucleus) C A A A A G G G C C C U U U U A G U Translation (in the cytoplasm) U A U transfer RNA (tRNA) mRNA
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5 C A A U A U C A A A A G G G C C C U U U U A G U Translation mRNA Immune System and Immune Response Getting sick is often a sign that your body is responding, fighting off invaders from outside Immune system : complex network of cells and organs that work together to defend your body from viruses, bacteria, fungi, and protozoa.
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Unit 6 - Nucleic Acids The Genetic Code Transcription,...

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