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Lesson Overview 12.1 Identifying the Substance of Genes Lesson Overview Identifying the Substance of Genes Griffith’s Experiments Griffith isolated two different strains of bacteria. Only one caused pneumonia. Lesson Overview Identifying the Substance of Genes Griffith’s Experiments When injecting mice with disease-causing bacteria, the mice died. When injecting mice with harmless bacteria, the mice stayed healthy. Lesson Overview Identifying the Substance of Genes Griffith’s Experiments First, Griffith took the S strain, killed them, and then injected the them into mice. Mice survived, showing that it wasn’t a toxin the bacteria produce. Lesson Overview Identifying the Substance of Genes Griffith’s Experiments In Griffith’s next experiment, he mixed the heat-killed S-strain with harmless R strain and injected the mixture into mice. The mice died. Lesson Overview Identifying the Substance of Genes Transformation Process called transformation - one type of bacteria is changed into another. Because transformed bacteria inherited ability to cause disease, Griffith concluded the transforming factor was a gene. Lesson Overview Identifying the Substance of Genes The Molecular Cause of Transformation Avery destroyed proteins, lipids, carbohydrates, and RNA. Transformation still occurred. Lesson Overview Identifying the Substance of Genes The Molecular Cause of Transformation Then destroyed DNA and transformation did not occur. Therefore, DNA was the transforming factor. Meant that DNA stores and transmits genetic information. Lesson Overview Identifying the Substance of Genes Bacteriophages Bacteriophage - virus that infects bacteria Lesson Overview Identifying the Substance of Genes The Hershey-Chase Experiment Hershey and Chase studied a bacteriophage with a DNA core and a protein coat. Wanted to determine if the protein or DNA changed bacteria Hershey and Chase grew viruses containing P-32 and S-35 Lesson Overview Identifying the Substance of Genes The Hershey-Chase Experiment Bacteria contained P-32 , found in DNA. Hershey and Chase confirmed Avery’s results - that DNA was the genetic material found in genes. Lesson Overview Identifying the Substance of Genes The Role of DNA DNA can store, copy, and transmit genetic information Lesson Overview 12.2 The Structure of DNA Lesson Overview Identifying the Substance of Genes Nucleic Acids and Nucleotides Located in nucleus. Made up of nucleotides. Three components: a 5-carbon sugar called deoxyribose, a phosphate group, and a nitrogenous base. Lesson Overview Identifying the Substance of Genes Nucleic Acids and Nucleotides DNA has four nitrogenous bases: adenine, guanine, cytosine, and thymine, or AGCT Lesson Overview Identifying the Substance of Genes Chargaff’s Rules Chargaff discovered the amount of [A] and [T] bases are almost equal. The same is true for guanine [G] and cytosine [C]. - [A] = [T] and [G] = [C] is known as “Chargaff’s rules.” Lesson Overview Identifying the Substance of Genes Franklin’s X-Rays Rosalind Franklin used X-ray diffraction that showed: - DNA has 2 strands twisted around each other. - The nitrogen bases are near the center. Lesson Overview Identifying the Substance of Genes The Work of Watson and Crick Franklin’s X-ray pattern enabled Watson and Crick to build a model of DNA. Built 3-D model of DNA in a double helix Lesson Overview Identifying the Substance of Genes Antiparallel Strands DNA strands are “antiparallel”— they run in opposite directions. Lets nitrogenous bases join at center and allows each strand to carry nucleotides. Lesson Overview Identifying the Substance of Genes Hydrogen Bonding Hydrogen bonds form between bases and hold strands together. Hydrogen bonds are weak and allow strands to separate. Lesson Overview Identifying the Substance of Genes Base Pairing Fit between A–T and G–C nucleotides called base pairing. EUKARYOTIC DNA REPLICATION Step 1 – Helicase unzips the DNA molecule. Step 2 – DNA Polymerase adds on complementary nucleotides. Step 3 – The lagging strand replicates in fragments instead of continually like the leading strand. Leading Strand Lagging Strand OKAZAKI FRAGMENTS Step 4 –Enzyme ligase joins the fragments on lagging strand. Step 5 – As replication continues, the strands twist back into helix. TELOMERES Are the tips of chromosomes make sure genes aren’t lost during replication. PROKARYOTIC DNA REPLICATION Starts at single point, and goes in 2 directions until the chromosome is copied. PROKARYOTIC VS. EUKARYOTIC DNA Replication Process [3D Animation] – Biology / Medicine Animations HD https://www.youtube.com/watch?v=27TxKoFU2Nw Lesson Overview Fermentation Lesson Overview 13.1 RNA Lesson Overview Fermentation The Role of RNA First step - copy DNA into RNA. RNA, like DNA, is a nucleic acid made of nucleotides. RNA uses the base sequence copied from DNA to make proteins. Lesson Overview Fermentation Comparing RNA and DNA Each nucleotide in both DNA and RNA is made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. Three differences between RNA and DNA: (1) Sugar in RNA is ribose (2) RNA is single-stranded. (3) RNA contains uracil (U) instead of thymine (T). Lesson Overview Fermentation Comparing RNA and DNA The cell uses DNA “master plan” to prepare RNA “blueprints.” DNA stays in nucleus, while RNA goes to ribosomes. Lesson Overview Fermentation Functions of RNA RNA is like a disposable copy of a segment of DNA, a working copy of a single gene. RNA assembes amino acids into proteins. Lesson Overview Fermentation Functions of RNA Three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA. Lesson Overview Fermentation Messenger RNA The RNA molecules that carry instructions are known as messenger RNA (mRNA) Lesson Overview Fermentation Ribosomal RNA Ribosomal RNA (rRNA) make up ribosomes. Lesson Overview Fermentation Transfer RNA Transfer RNA (tRNA) transfers amino acids to the ribosome Lesson Overview Fermentation Making RNA - Transcription Transcription – Turning DNA into RNA. Lesson Overview Fermentation Transcription In prokaryotes, RNA and protein synthesis occurs in the cytoplasm. In eukaryotes, RNA is produced in the nucleus and moves to the cytoplasm to produce proteins. Lesson Overview Fermentation Transcription Requires RNA polymerase, which separates DNA strands to assemble complementary strand of RNA. Lesson Overview Fermentation Promoters RNA polymerase binds to promoters. Promoters show RNA polymerase where to begin making RNA. Similar signals cause transcription to stop. Lesson Overview Fermentation RNA Editing Parts of RNA are cut out and stay in the nucleus are called introns. The remaining pieces, known as exons, are joined together into the final mRNA, which exits the nucleus. Lesson Overview Ribosomes and Protein Synthesis Lesson Overview 13.2 Ribosomes and Protein Synthesis Lesson Overview Ribosomes and Protein Synthesis The Genetic Code First step - transcribe DNA to RNA. Contains code for making proteins. The genetic code is read three “base letters” at a time and corresponds to a single amino acid. Lesson Overview Ribosomes and Protein Synthesis The Genetic Code Proteins are made by joining amino acids together into long chains, called polypeptides. There are about 20 amino acids. Lesson Overview Ribosomes and Protein Synthesis The Genetic Code The type and order of amino acids determine the properties of proteins. Order of amino acids affects the shape of the protein, which determines its function. Lesson Overview Ribosomes and Protein Synthesis The Genetic Code Each three-letter “word” in mRNA is known as a codon. A codon specifies a single amino acid. Lesson Overview Ribosomes and Protein Synthesis Start and Stop Codons The “start” codon AUG begins protein synthesis. Then mRNA is read, three bases at a time, until it reaches a “stop” codon, which ends translation. Lesson Overview Ribosomes and Protein Synthesis Translation The decoding of mRNA into amino acids is called translation. Lesson Overview Ribosomes and Protein Synthesis Steps in Translation mRNA is transcribed in the nucleus and then translated in the cytoplasm. Lesson Overview Ribosomes and Protein Synthesis Steps in Translation Translation begins when a ribosome attaches to mRNA. As the ribosome reads mRNA, it directs tRNA to bring amino acid. Lesson Overview Ribosomes and Protein Synthesis Steps in Translation Each tRNA molecule carries one amino acid. Each tRNA has three unpaired bases, called the anticodon — which compliment one mRNA codon. Lesson Overview Ribosomes and Protein Synthesis Steps in Translation Peptide bonds form between amino acids At the same time, the bond holding tRNA to its amino acid is broken. Lesson Overview Ribosomes and Protein Synthesis Steps in Translation The polypeptide chain grows until the ribosome reaches a “stop” codon, which completes translation. Lesson Overview Ribosomes and Protein Synthesis The Roles of tRNA and rRNA in Translation rRNA holds ribosomal proteins in place. Lesson Overview Ribosomes and Protein Synthesis The Molecular Basis of Heredity Genes contain instructions for assembling proteins. Lesson Overview Ribosomes and Protein Synthesis The Molecular Basis of Heredity Gene expression - the way DNA, RNA, and proteins put genetic information into action in living cells. Lesson Overview Ribosomes and Protein Synthesis The Molecular Basis of Heredity There is a near-universal nature in the genetic code. Although some organisms show slight variations in the amino acids assigned to particular codons, the code is always read three bases at a time and in the same direction. Despite their enormous diversity in form and function, living organisms display remarkable unity at life’s most basic level, the molecular biology of the gene. Lesson Overview Ribosomes and Protein Synthesis Lesson Overview 13.3 Mutations Lesson Overview Ribosomes and Protein Synthesis Types of Mutations Cells can make mistakes, called mutations Lesson Overview Ribosomes and Protein Synthesis Types of Mutations All mutations fall into two basic categories: Gene mutations - changes in a single gene Chromosomal mutations changes in whole chromosomes. Lesson Overview Ribosomes and Protein Synthesis Gene Mutations Point mutations - changes in one or a few nucleotides. Changes can be passed on to every cell that develops from the original one. Lesson Overview Ribosomes and Protein Synthesis Gene Mutations Point mutations include substitutions, insertions, and deletions. Lesson Overview Ribosomes and Protein Synthesis Substitutions In a substitution, one base is changed to a different base. Usually affect a single amino acid Lesson Overview Ribosomes and Protein Synthesis Insertions and Deletions Insertions and deletions are mutations in which one base is inserted or removed. Called frameshift mutations because they shift the “reading frame” of the genetic message. Lesson Overview Ribosomes and Protein Synthesis Chromosomal Mutations Chromosomal mutations involve changes in the number or structure of chromosomes. Four types: deletion, duplication, inversion, and translocation. Lesson Overview Ribosomes and Protein Synthesis Chromosomal Mutations Deletion involves the loss of all or part of a chromosome. Lesson Overview Ribosomes and Protein Synthesis Chromosomal Mutations Duplication produces an extra copy of all or part of a chromosome. Lesson Overview Ribosomes and Protein Synthesis Chromosomal Mutations Inversion reverses the direction of parts of a chromosome. Lesson Overview Ribosomes and Protein Synthesis Chromosomal Mutations Translocation occurs when part of one chromosome breaks off and attaches to another. Lesson Overview Ribosomes and Protein Synthesis Effects of Mutations Genetic material can be altered by natural or artificial means. Resulting mutations may or may not affect an organism, most do not. Some mutations that affect individual organisms can also affect a species or even an entire ecosystem. Lesson Overview Ribosomes and Protein Synthesis Effects of Mutations Many mutations are produced by errors in genetic processes. An incorrect base is inserted roughly once in every 10 million bases. Small changes can accumulate over time. Lesson Overview Mutagens Ribosomes and Protein Synthesis Some mutations arise from mutagens - chemical or physical agents in the environment. Chemical mutagens include certain pesticides, plant alkaloids, tobacco smoke, and environmental pollutants. Physical mutagens include forms of electromagnetic radiation, such as X-rays and UV light. Stress can also be a factor. Lesson Overview Ribosomes and Protein Synthesis Harmful Effects The most harmful mutations dramatically change protein structure or gene activity. Example: Sickle Cell Disease Lesson Overview Ribosomes and Protein Synthesis Beneficial Effects Some mutations can be highly advantageous to an organism or species. Example: Pesticide Resistance and Polyploidy