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CHAPTER 13: DNA, RNA, and Proteins FIZZ 1 Essential Questions: 1. What is the Central Dogma of Biology? CHAPTER 13: DNA, RNA, and Proteins FIZZ 1 Essential Questions: 2. What is DNA? CHAPTER 13: DNA, RNA, and Proteins FIZZ 1 Essential Questions: 3. How is DNA related to traits? CHAPTER 13: DNA, RNA, and Proteins FIZZ 1 Essential Questions: 4. What is the Genetic Code? DNA- The Genetic Material • Why should I care about DNA? • DNA stores the information that tells cells which proteins to make • Your proteins give you your physical/chemical/ identity • Your DNA is different from everyone else’s DNA on earth Does DNA have anything to do with why I am so special? • Yes, it’s the variability of DNA that makes us all different! The Central Dogma of Biology DNA RNA PROTEINS DNA is transcribed into RNA RNA is translated into Proteins Proteins give you your traits or Phenotype Searching for the Genetic Material • Griffith - Discovered the transformation of harmless R strain Bacteria by heat killed S bacteria • Avery – Identified DNA as the transformative agent • Hershey & Chase –Studied bacteriophages and proved DNA was the source of hereditary information Who Discovered the Structure of DNA? James Watson & Francis Crick discovered the structure of DNA after observing an X-ray picture of it taken by Rosalind Franklin The Structure of DNA The Structure of DNA is both complex and simply elegant DNA is a polymer of Nucleotidesremember a polymer is like a chain of beads- DNA is made of 2 chains There are 4 different Nucleotides (beads) abbreviated as A, T G, or C The Base on one chain “complements” and makes a bond with the base on the opposite chain The bases are bound together by hydrogen bonds. The two strands are twisted together DNA Structure DNA is a polymer of nucleotides (the beads on the chain) Each Nucleotide contains 1 Nitrogenous base + 1 phosphate group + 1 sugar In DNA the sugar is deoxyribose Nucleotide Nitrogenous Bases The Structure of DNA There are 4 different Nucleotides identified by their Nitrogenous Bases: Adenine Guanine (the pyrimidines) Cytosine Thymine (the purines) The Bases are said to “complement” one another - A bonds to T, G bonds to C according to the base pairing rules(also called Chargraffs Rules) The bases are bound to each other by hydrogen bonds. The Structure of DNA The DNA Double Helix is composed of 2 interconnected nucleotide chains The nucleotide chains are composed of a Sugar-Phosphate backbone, with bases in the middle The Nucleotides are joined by Phosphodiester bonds The two strands are twisted together and joined by Hydrogen bonds between he bases Structure of DNA DNA Replication Why does DNA replicate? Cells get worn out, new cells must be made New cells must make exact copies of themselves Copies of replicated genes can be passed on to offspring How is DNA Replicated? 1. Helicase breaks hydrogen bonds in the middle of the strand, creating a replication fork 2. Unpaired bases form new bonds with free nucleotides in the cell How is DNA Replicated? 3. New strand is rewound together by DNA Polymerase, creating 2 identical DNA molecules 4. Sometimes replication errors make a mistake (A bonds to a G); 5. There are 3 x 109 bases in the average cell 6. Takes about 4 hours for a cell to replicate its DNA 3. The process is SEMIConservative, ie each new DNA molecule has one old strand Transcription DNA is located in the nucleus of the cell DNA CANNOT leave the nucleus of the cell because it is double stranded So How does it get out? http://www.dnalc.org/resources/3d/12-transcription-basic.html Transcription Mr. Dougherty! I am afraid for the DNA, it can’t get to the ribosome! What will it do? Relax, RNA is the key! What is RNA? •A nucleic acid that is similar to DNA •Ribose is the sugar •Instead of thymine, Uracil •Single stranded Steps of Transcription 1. DNA strand unwinds via RNAPolymerase (not helicase) 2. Free nucleotides bond to bases, except U in RNA bonds to A from DNA 3. RNA polymerase joins single stranded RNA together 4.Messenger RNA (mRNA) moves to the ribosome in the cytoplasm (or on the Rough ER) Transcription Animation of Transcription! http://www.johnkyrk.com/DNAtranscription.html Translation (Protein Synthesis) What is protein synthesis? The Conversion of RNA to Amino Acids which make up proteins Why is it called translation? The genetic code (ATCG) is translated into a protein Where does it occur? At the ribosome in the cytoplasm Globular Protein found in Human Blood (serum albumin) Translation and the Genetic Code RNA is composed of 3 letter “words” called CODONS Each codon of RNA represents a specific Amino Acid For instance AUG is the start codon, and UUU represents the amino acid Phe (phenylalanine) Why is it called translation? The genetic code (ATCG) is translated into a protein Translation and the Genetic Code RNA is composed of 3 letter “words” called CODONS Each codon of RNA represents a specific Amino Acid For instance AUG is the start codon, and UUU represents the amino acid Phe (phenylalanine) Why is it called translation? The genetic code (ATCG) is translated into a protein Genetic Code Problem If the DNA code is AAT GCG TTT CGC ATA TAT Then the RNA compliment is ___ ___ ___ ___ ___ ___ and the Amino Acid sequence that results is ____ ____ ____ ____ ____ ____ How Does Translation Occur? The 3 Steps of Translation 1. Initiation A. Ribosome attaches to mRNA (each 3 bases is called a codon) B. tRNA brings anticodon and AA to ribosome 2. Elongation A. More tRNA’s bring more AA’s to ribosome B. AA’s connected together to make polypeptides (by peptide bonds) 3. Termination A. Ribosome reaches a STOP signal on mRNA B. Polypeptide (protein) is broken off and becomes part of the human body C. Golgi apparatus modifies completed protein; ER transports it in/out of cell Translation- The Movie Translation Animation Part 2! Translation Animation Scary Translation Scary Animation of Translation! http://www.youtube.com/watch?v=983lhh2 0rGY The processes of transcription and translation are the same in all living organisms! Blue Whale Tarantula CHAPTER 14: Genes in Action Essential Questions: What is DNA? What is the Central Dogma of Biology? What is the Genetic Code? How is DNA related to traits? Control of Gene Expression in Eukaryotes In eukaryotes, cells differ in which genes are being expressed based on cell function – ex. nerve vs. muscle. •Genes in eukaryotic cells are turned on and off like a light switch. The genes that are turned on in a muscle cell are different than the genes that are turned on in a nerve cell. •Gene expression is what makes cells different in a multicellular organism Nerve Cell vs. Muscle Cell Gene Mutations A Mutation is a change in the sequence of bases within a gene Causes: • Mutations can be spontaneous or caused by environmental influences called mutagens. • Mutagens include radiation (X-rays, UV radiation), and organic chemicals (in cigarette smoke and pesticides). Types of Mutations Frameshift mutations – • one or more bases are inserted or deleted from a sequence of DNA • can result in nonfunctional proteins • can result in no protein at all – stop codon where there shouldn’t be one Point mutations (3 Types) – • One base is substituted for another • May result in change of amino acid sequence • May not affect protein at all Types of point mutations • 1. Silent mutation - the change in the codon results in the same amino acid • Ex: UAU UAC both code for tyrosine • 2. Nonsense mutation - a codon is changed to a stop codon; resulting protein may be too short to function – Ex: UAC UAG (a stop codon) • 3. Missense mutation - involves the substitution of a different amino acid, the result may be a protein that cannot reach its final shape – Ex: Hbs which causes sickle-cell disease Repair of Mutations • DNA polymerase proofreads the new strand against the old strand and detects mismatched pairs, reducing mistakes to one in a billion nucleotide pairs replicated. • If errors occur in sex cells – mutation may be passed onto offspring • If errors occur in body cells - cancer may result Genetic Diseases Autosomal dominant disease Presence of dominant allele means that individual will have the disease Autosomal recessive disease Disease only present when BOTH recessive alleles are present Sex-linked Dominant Disease present when dominant allele is present on either sex chromosome Sex-linked Recessive Disease present when recessive allele is present on either sex chromosome Common Genetic Diseases Huntington’s Disease Autosomal dominant ; Neuromuscular disease; degeneration of muscle tissue; onset in early 30’s. Folk Singer Woody Guthrie had the disease Cystic Fibrosis Autosomal Recessive; Defective Protein is made that creates excess mucus; clogs lungs. Color Blindness Sex-linked recessive Inablity to distinguish colors (8% of male population) Some Genetics Diseases Hemophilia Sex-linked recessive Inablity of blood to clot Nicholas, Czar of Russia (Mid 1800’s) child was hemophiliac Muscular Dystrophy Sex-linked recessive Tay-Sach’s Disease Autosomal Recessive Degeneration of Central Nervous System; infant mortality Changes in Chromosome Number • Nondisjunction – occurs when: – In meiosis I, homologous pair both go into the same daughter cell or – In meiosis II, the sister chromatids both go into the same gamete. • The result: – Trisomy (3 copies of a single chromosome) or – Monosomy (1 copy of a single chromosome) Nondisjunction in Meiosis I Changes in Chromosome Structure • Mutation - a permanent genetic change. • Chromosome mutation - a change in chromosome structure • Radiation, organic chemicals, or even viruses may cause chromosomes to break, leading to mutations. • Types of chromosomal mutations: inversion, translocation, deletion, and duplication. Deletions • Deletions occur when a single break causes a lost end piece, or two breaks result in a loss in the interior. • An individual inherits a normal chromosome from one parent and a chromosome with a deletion from the other parent • No longer has a pair of alleles for each trait • A syndrome can result – type depends on chromosome(s) affected. Williams Syndrome • Chromosome 7 loses an end piece • Children have a pixie look (turned-up noses, wide mouth, small chin, large ears) • Poor academic skills, good verbal and musical abilities • Skin ages prematurely from lack of the gene that controls the production of elastin (also affects cardiovascular health). Duplication • Duplication results in a chromosome segment being repeated in the same chromosome – Produces extra alleles for a trait. • Ex: An inverted duplication in chromosome 15 causes inv dup 15 syndrome – Poor muscle tone, mental retardation, seizures, curved spine, and autistic characteristics Duplication Translocation • Translocation is exchange of chromosomal segments between two, non-homologous chromosomes. – Ex: Alagille syndrome results from a deletion of chromosome 20 or a translocation that disrupts an allele on chromosome 20. – Distinctive face, abnormalities of eyes & internal organs, and severe itching. Translocation: Alagille Syndrome Inversion • Inversion involves a segment of a chromosome being turned 180 degrees • The reverse sequence of alleles can alter gene activity. • Crossing-over between inverted and normal chromosomes can cause duplications and deletions in resulting chromosomes. Inversion