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C11- DNA and Genes Chapter 11 Contents • • • • 11-1 DNA: The Molecule of Heredity 11-2 From DNA to Protein Protein Synthesis video 11-3 Genetic Changes 11-1 DNA: The Molecule of Heredity • Genetic info in DNA controls organism’s traits 11-1 DNA: The Molecule of Heredity • Genetic info in DNA controls organism’s traits • Determines structure of proteins built 11-1 DNA: The Molecule of Heredity • Genetic info in DNA controls organism’s traits • Determines structure of proteins built • Hershey & Chase (1952) used radioactively tagged viruses to infect bacteria and proved DNA is genetic material 11-1 DNA: The Molecule of Heredity • Genetic info in DNA controls organism’s traits • Determines structure of proteins built • Hershey & Chase (1952) used radioactively tagged viruses to infect bacteria and proved DNA is genetic material Nucleotide Structure • DNA polymer of repeating units called nucleotides. Nucleotide Structure • DNA polymer of repeating units called nucleotides. • 3 parts – Simple sugar – Phosphate • Phosphorus w/ 4 O – Nitrogenous base Nucleotide Structure • DNA polymer of repeating units called nucleotides. • 3 parts – Simple sugar – Phosphate • Phosphorus w/ 4 O – Nitrogenous base • C ring w/ 1 or more N & a base – Adenine (A) – Cytosine (C) – Guanine (G) – Thymine (T) Nucleotides • Join in long chains • with phosphates connecting • to sugar of next unit • to form a backbone Nucleotides • Join in long chains • with phosphates connecting • to sugar of next unit • to form a backbone • with the bases sticking out like the teeth of a zipper. • Adenine = Thymine • Guanine = Cytosine Structure of DNA • James Watson & Francis Crick (1953) unraveled the structure of DNA. • Double Helix structure Nucleotide Sequence • Forms unique genetic information of organism Nucleotide Sequence • Forms unique genetic information of organism • Can be used to determine evolutionary relationships between organisms Nucleotide Sequence • Forms unique genetic information of organism • Can be used to determine evolutionary relationships between organisms • Or familial relationships • DNA can identify victims or criminals Replication of DNA • Copies DNA in chromosome during interphase Replication of DNA • Copies DNA in chromosome during interphase • Enzyme breaks the hydrogen bond between bases Replication of DNA • Copies DNA in chromosome during interphase • Enzyme breaks the hydrogen bond between bases • Complimentary base pairing allows duplication Replication of DNA • • • • Copies DNA in chromosome during interphase Enzyme breaks the hydrogen bond between bases Complimentary base pairing allows duplication Each strand is a template 11-2 From DNA to Protein • DNA controls the production of proteins. • Proteins are key cell structures & regulators of cell functions. 11-2 From DNA to Protein • DNA controls the production of proteins. • Proteins are key cell structures & regulators of cell functions. • RNA, another nucleic acid carries out DNA’s instructions 11-2 From DNA to Protein • DNA controls the production of proteins. • Proteins are key cell structures & regulators of cell functions. • RNA, another nucleic acid carries out DNA’s instructions • Structure differs 3 ways – Single-stranded – Sugar is ribose – Uracil replaces thymine Three Types of RNA • • • • Protein assembly line: Messenger RNA (m-RNA) Ribosomal RNA (r-RNA) Transfer-RNA (t-RNA) Three Types of RNA • Protein assembly line: • Messenger RNA (m-RNA) – Brings instructions from DNA to ribosome in the cytoplasm • Ribosomal RNA (r-RNA) • Transfer-RNA (t-RNA) Three Types of RNA • Protein assembly line: • Messenger RNA (m-RNA) – Brings instructions from DNA to ribosome in the cytoplasm • Ribosomal RNA (r-RNA) – Reads instructions to assemble protein by binding to m-RNA • Transfer-RNA (t-RNA) Three Types of RNA • Protein assembly line: • Messenger RNA (m-RNA) – Brings instructions from DNA to ribosome in the cytoplasm • Ribosomal RNA (r-RNA) – Reads instructions to assemble protein by binding to m-RNA • Transfer-RNA (t-RNA) – Delivers amino acids for assembly to ribosome Transcription • Occurs in the nucleus by enzymes copying part of the DNA – Enzyme unzips DNA – Assembles singlestrand copy Transcription • Occurs in the nucleus by enzymes copying part of the DNA – Enzyme unzips DNA – Assembles singlestrand copy – DNA rezips after mRNA detaches Transcription • Occurs in the nucleus by enzymes copying part of the DNA – Enzyme unzips DNA – Assembles singlestrand copy – DNA rezips after mRNA detaches – m-RNA leaves nucleus by nuclear pore to enter cytoplasm Transcription • Occurs in the nucleus by enzymes copying part of the DNA – Enzyme unzips DNA – Assembles singlestrand copy – DNA rezips after mRNA detaches – m-RNA leaves nucleus by nuclear pore to enter cytoplasm – Carries instructions to ribosome Translation • Occurs in the ribosome • Process of converting series of bases into chain of amino acids forming a protein Translation • Occurs in the ribosome • Process of converting series of bases into chain of amino acids forming a protein – r-RNA reads sequence of 3 bases (codon) Translation • Occurs in the ribosome • Process of converting series of bases into chain of amino acids forming a protein – r-RNA reads sequence of 3 bases (codon) – t-RNA anticodon matches up with the codon from m-RNA and supplies the amino acid needed Translation • Occurs in the ribosome • Process of converting series of bases into chain of amino acids forming a protein – r-RNA reads sequence of 3 bases (codon) – t-RNA anticodon matches up with the codon from m-RNA and supplies the amino acid needed – Ribosome translates the next codon until finished assembling the protein RNA & Protein Synthesis RNA Processing • Introns- noncoding nucleotide sequences • Exons- expressed sections of nucleotides • Enzymes cut out the introns & paste the exons together Genetic Code • Amino acids are the building blocks of proteins. • A sequence of 3 nucleotide bases code for each of the 20 amino acids. • 64 different codons in mRNA • AUG start codon • UAA stop codon • All organisms use the same genetic code. Translating the m-RNA Code • T-RNA leaves amino acid in position to form peptide bond with previous amino acid Translating the m-RNA Code • T-RNA leaves amino acid in position to form peptide bond with previous amino acid • The ribosome continues to assemble amino acids until stop codon is reached. Translating the m-RNA Code • T-RNA leaves amino acid in position to form peptide bond with previous amino acid • The ribosome continues to assemble amino acids until stop codon is reached. • Translation is complete Translating the m-RNA Code • T-RNA leaves amino acid in position to form peptide bond with previous amino acid • The ribosome continues to assemble amino acids until stop codon is reached. • Translation is complete • Amino acid chain is released & twists into complex folded shape of protein Translating the m-RNA Code • T-RNA leaves amino acid in position to form peptide bond with previous amino acid • The ribosome continues to assemble amino acids until stop codon is reached. • Translation is complete • Amino acid chain is released & twists into complex folded shape of protein • Become enzymes & structures 11-3 Genetic Changes • Mutation- any change in DNA sequence • Caused by errors in – Replication – Translation – Cell division – Or by external agents such as UV or chemical exposure Mutations in Reproductive Cells • Changes in the sequence of nucleotides can cause: – Altered gene in offspring – New traits – Nonfunctional protein with structural or functional problems in cells – Embryo may not survive – Positive effect Mutations in Body Cells • Does not pass on to offspring • May cause problems for the individual • Impair function of the cell • Contributes to aging • Can cause cancer by making cells reproduce rapidly Effects of Point Mutations • Point mutation - Change in a single base pair in DNA • Can change entire structure of the protein • Error may or may not affect protein function • Ex. Sickle cell anemia Frameshift Mutations • A single base is added to or deleted from DNA • Shifts the reading of the codons by one base • Nearly every amino acid after the insertion or deletion will be changed Chromosomal Alterations • Chromosomal mutations • Deletions -Parts break & are lost during mitosis or meiosis • Insertions- Parts rejoin incorrectly • Inversions- Rejoin backwards • Translocations- Join other chromosomes • Common in plants Causes of Mutations • Mutagens- agents that cause change in DNA – Radiation • X-rays • Gamma rays • Ultraviolet light • Nuclear radiation – Chemicals • Dioxins • Asbestos • Benzene • Formaldehyde – High temperatures 6-legged frog aflatoxin Repairing DNA • Repair mechanisms have evolved: • Enzymes proofread DNA & replace incorrect nucleotides. • The greater the exposure to the mutation, the less likely it can be corrected. • Limit exposure to mutagens.