440 likes | 578 Views
Chapter 12. DNA and RNA. 1928 – Griffith Discovered bacteria transferred something between them that changed them into a new strain. Called this “bacterial transformation”. Historical Development. Griffith’s Experiment. Section 12-1.
E N D
Chapter 12 DNA and RNA
1928 – Griffith • Discovered bacteria transferred something between them that changed them into a new strain. • Called this “bacterial transformation”. Historical Development
Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Harmless bacteria (rough colonies) Control(no growth) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
1944 – Avery • Determined the transforming factor was DNA. • He destroyed different parts of the bacteria, and only when the DNA was destroyed did transformation not occur. Historical Development
1952 – Hershey and Chase • Using a blender and bacteriophage, determined that DNA, not protein, was the genetic material. Historical Development
Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium
1952 – Rosalind Franklin • Used x-ray crystallography to show the structure of DNA was a helix. Historical Development
1953 – Watson and Crick • Determined the structure of DNA was a double helix, and proposed a model for DNA replication. Historical Development
DNA is a chain (polymer) of nucleotides. • A nucleotide consists of a sugar, phosphate and nitrogenous base. DNA Structure
DNA Nucleotides Section 12-1 Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose
DNA is a double helix (twisted ladder). • Two nucleotide polymers are held together by weak hydrogen bonds. • Nitrogen bases always pair up this way: • Adenine with thymine A-T • Cytosine with guanine C-G • The backbone of the ladder is alternating sugars and phosphates. • The steps of the ladder are the base pairs. DNA Structure
Structure of DNA Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
12-2 Chromosomes and DNA Replication
Prokaryotic cells (bacteria) • No nucleus • Single circular chromosome • Bacterial DNA is about 1.6mm long • Eukaryotic cells (all else) • 1000X more DNA than bacteria • DNA in nucleus (protected) • Multiple chromosomes • Human DNA (combined) is over 1 meter long DNA and Chromosomes
Prokaryotic Chromosome Structure Chromosome E.coli bacterium Bases on the chromosome
Eukaryotic DNA is tightly packed and folded. It is wound about proteins called histones. DNA and Chromosomes
Chromosome Structure of Eukaryotes Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones
A cell copies its DNA before dividing. • The DNA uncoils. • Then it “unzips” – the two strands separate along the weak hydrogen bonds. • Complimentary nucleotides are added with the help of the enzyme DNA Polymerase. • The result: two identical molecules of DNA. DNA Replication
DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand
C:\Users\Carolyn\Videos\RealPlayer Downloads\How DNA Copies Itself.mp4 DNA Replication
12-3 RNA and Protein Synthesis
Single-stranded chain of nucleotides No thymine - its replaced by uracil Sugar is ribose, not deoxyribose RNA Structure
Messenger RNA (mRNA) • Carries a copy of the genetic code (gene) for a protein into the cytoplasm. • Ribosomal RNA (rRNA) • A component of ribosomes where proteins are made. • Transfer RNA (tRNA) • Carries amino acids to the ribosome for assembly into proteins. Types of RNA
The process of DNA making mRNA in the nucleus is called transcription. • A section of DNA (gene) unwinds and separates • Enzymes add complimentary RNA nucleotides to make mRNA. • mRNA leaves the nucleus and goes to a ribosome in the cytoplasm. • What is the complimentary nucleotide sequence for this DNA sequence? • DNA = A-T-T-C-G-C-G Transcription
Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA
C:\Users\Carolyn\Videos\RealPlayer Downloads\Transcription.flv Transcription
The process of mRNA being read on a ribosome to make a protein is called translation. • mRNA attaches to a ribosome. • tRNA carries amino acids to the ribosome. • The mRNA codon (3 nucleotide sequence) matches up with a complimentary tRNAanticodon (complimentary sequence). • The amino acid is dropped off and added the growing polypeptide chain. • What is the amino acid sequence for the following mRNA sequence? See the universal genetic code chart… • mRNA = AUAAGCGCU Translation
C:\Users\Carolyn\Videos\RealPlayer Downloads\Translation.flv Translation
C:\Users\Carolyn\Videos\RealPlayer Downloads\From DNA to Protein.mp4 Transcription and Translation
C:\Users\Carolyn\Videos\RealPlayer Downloads\DNA Transcription and Protein Assembly.mp4 Transcription and Translation
Proteins are made of several polypeptide chains folded together. • The shape is important to how the protein functions. • One gene codes for the production of one polypeptide. • Therefore, several genes are needed to make one protein. Genes and Proteins
12-4 Gene Mutations
Mistakes made when DNA is copied are called mutations. Two kinds: gene and chromosome mutations Kinds of Mutations
Gene mutations affect only one gene. • There is a change in the sequence of bases in DNA. • This causes the protein made by that gene to be incorrect. (sometimes) • Ex: lactose intolerance Gene Mutations
Changes in the number or structure of chromosomes are called chromosome mutations. • Ex: An extra chromosome causes Down Syndrome. Chromosome Mutations
Substances that can cause mutations are called mutagenic agents. • UV light, chemicals, radiation Mutagens
Inherited only if the mutation occurs in a sex cell. • Harmful mutations – cause many genetic disorders. • Ex: cystic fibrosis • Neutral mutations – have no effect on gene expression or protein function (most). • Beneficial mutations – source of genetic variability. • Breeders artificially select for these traits Significance of Mutations