Chapter 12 DNA & RNA - PowerPoint Presentation

Chapter 12 DNA & RNA

I.DNA A. Griffith & Transformation Frederick Griffith was trying to figure out how bacteria made people sick-how they cause a certain type of pneumonia. He isolated 2 strains(types) from mice-both cultured well,but only one caused pneumonia.The culture of the disease causing bacteria were __________________colonies while the other was rough. smooth

1-Griffith’s experiments (1928) Mice injected w/ disease –causing strain got sick and died and nothing happened if injected w/other strain…He wondered if the disease-causing type made a toxin…? So he took some of disease strain and heated to kill bacteria and then injected into mice….mice survived suggesting it was not a toxin producing disease

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment

Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment

2-Transformation He mixed his heat –killed w/ live harmless bacteria and injected into mice…..________________________ Somehow the disease –causing strain passed their disease capacity to harmless bacteria….. disease –causing strain found in lungs He called this changing of one bacteria by the genes of another _____________________....Thus a factor(gene) from heat killed disease –causing strain was passed on. Mice developed pneumonia transformation

B. Avery & DNA Team of scientists lead by Avery in 1944 repeated Griffith’s experiment in order to determine which molecule was responsible for the transformation.They made an extract from the heat-killed bacteria and treated it w/enzymes that kill proteins,lipids and other molecules,inc. RNA

Avery cont’d ____________________still occurred so the above molecules were not responsible for transformation They repeated the experiment but used enzymes that kill____________, stopping transformation…. Therefore ________caused the transformation and thus stores and transmits genetic info transformation DNA DNA

C. The Hershey –Chase Experiment 1952-Alfred Hershey and Martha Chase studied viruses-disease-causing particles smaller than a cell. ______________________-virus that infects bacteria.They have a DNA or RNA core and a protein coat…They attach to the surface of a bacterium and inject genetic info into cell.The viral genes act to produce many new bacteriophages and eventually destroy bacterial cell,w/_____________bursting out. bacteriophage viruses

They grew viruses in cultures containing _________________________________,mixed them w/bacteria and waited a few min. for viruses to inject genetic material. Then they separated the bacteria from the viruses and tested bacteria for radioactive marker…..nearly all the radioactivity was P-32-found in _________----thus concluding it was the genetic material was DNA ! Radioactive markers DNA

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Section 12-1 Figure 12–4 Hershey-Chase Experiment

D. The Components and Structure of DNA Scientists questioned how the DNA molecule could do three things 1)carry info from 1 generation to the next 2)putting that info to work and 3)could be easily copied DNA is a long molecule made of units called ___________________________________________- nucleotides

The nucleotide is made of 3 basic parts:______________________(sugar), a phosphate group and a_________________________________ deoxyribose Nitrogenous base

2 nitrogenous bases are purines(have 2 rings):___________________________(A)and_______(G) 2 other nitrogenous bases are pyrimidines (have 1 ring):____________________(C)and ____________________________(T ) Adenine ,guanine Cytosine and thymine -- backbone made by sugar and phosphate w/ bases sticking out sideways

Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose Figure 12–5 DNA Nucleotides Section 12-1

1-_______________________Rules-discovered that %’s of Cytosine and guanine were almost equal in DNA and the same was true for adenine and thymine….Thus A pairs w/T and C w/ G-BASE PAIRING Chargaff’s Rules

Percentage of Bases in Four Organisms Section 12-1 Source of DNA A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.8 27.5 22.2 22.6 Human 30.9 29.4 19.9 19.8

2- X-ray evidence-1950’s –Rosalind Franklin used X-ray diffraction to learn about DNA structure----The scattered X pattern seen begins to show the __________-partial TWISTED STRUCTURE of DNA helix

3---Double helix_ Watson and Crick -2 strands wound around each other---like the twisted ladder or spiral staircase Strands held together by H-bonds

Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Figure 12–7 Structure of DNA Section 12-1

Interest Grabber A Perfect Copy When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells. Section 12-2

I Section 12-2 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

II. Chromosomes & DNA Replication A-DNA & Chromosomes In cytoplasm in prokaryotes In _______________________found in cell nucleus in the form of a number of chromosomes(46 humans,8 Drosophilia and 22 Sequoia trees) eukaryotes

1--DNA length 1.6 mm in E.coli(has 4,639,221 base pairs)---obviously it must be tightly folded

2-Chromosome Structure Eukaryotic cells have about 1000 times as many base pairs of DNA than a bacterium Humans cells have ~ 1 m DNA Eukaryotic chromosomes contain DNA and a protein ,which together make _____________________-consisting of DNA tightly packed around proteins called histones chromatin

DNA and histone together make beadlike_____________________________ Nucleosomes pack together to make thick fibers,drawn together during mitosis…also separating Role of nucleosomes-fold great lengths of DNA into tiny spaces nucleosomes

Chromosome E. coli bacterium Bases on the chromosome Prokaryotic Chromosome Structure Section 12-2

Figure 12-10 Chromosome Structure of Eukaryotes Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2

B. DNA Replication Each strand of DNA double helix has all the info to___________________________by base pairing Strands are complementary In prokaryotes,this begins @single point and proceeds-often in 2 directions In Eukaryotes,DNA replication begins @ 100’s of places,going both directions until complete__________________________is where replication occurs Reconstruct the other half Replication fork

1-Duplicating DNA __________________________or duplication of DNA happens before cell division---ensuring each cell has a complete set of DNA molecules Each strand of a double helix serves as a _____________________or model for new strand A pairs w/ T and C w/ G replication template

2-How Replication Occurs Carried out by a series of enzymes that unzip a molecule ____________________________________ joins individual nucleotides to make a DNA molecule….also proof reads the new strands DNA polymerase

Figure 12–11 DNA Replication Section 12-2 Growth Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand

III. RNA & Protein Synthesis The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. A) The structure of RNA Long chain of nucleotides3 main differences between DNA & RNA:1--Sugar is _________________2---Generally single-stranded3---RNA contains ________________(U) in place of thymine (T) genes uracil ribose

B. Types of RNA Main job=_________________-ie the assembly of amino acids into proteins 3 Types: ____________________(mRNA)-carry copies for instructions from DNA to rest of cell ____________________(rRNA)-type of RNA that helps make up ribosomes,where proteins assembled________________(tRNA)transfers each amino acid to the ribosome as it is coded for on mRNA. Protein synthesis messenger ribosomal Transfer

from to to make up Concept Map Section 12-3 also called which functions to also called also called which functions to which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNA Carry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNA Ribosome Ribosomes

C. Transcription -produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA Requires enzyme known as _______________________________________-binds to DNA and separates DNA strands.Then uses one strand as template to make RNAThe enzyme only binds to areas known as promoters-signals that indicate where to make RNA.Similar signals tell where to stop RNA-polymerase

RNA DNA RNA polymerase Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only)

D. RNA editing ________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins _______________________-DNA sequence that does code for protein introns exons

E. Genetic Code ______________________-chain of amino acids=proteins _________________-3 consecutive nucleotides that specify a specific amino acid Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine polypeptide codon

 The Genetic Code Section 12-3

Universal code 64 possible 3 base codons AUG can specify methionine or start codon 3 stop codons that do not code for an amino acid

F. Translation ______________________reads the instructions for the order in which amino acids should be joined by reading mRNA ____________________________is the decoding of an mRNA message into a polypeptide(protein) Before translation occurs,mRNA is transcribed from DNA and released into __________________________. Translation begins when mRNA molecule in cytoplasm attaches to a _____________________. ribosome translation cytoplasm ribosome

As each codon of the mRNA moves through the moves through the ribosome,_____________brings in the proper,indicated amino acid and transferred to polypeptide chain Each tRNA carries one kind of amino acid __________________ is a group of 3 bases on a tRNA that are complementary to a mRNA codon Ribosome forms a _________________bond between amino acids and breaks tRNA bond releasing it Protein keeps growing until ribosome reaches stop codon on mRNA tRNA anticodon peptide

Figure 12–18 Translation Section 12-3

Figure 12–18 Translation (continued) Section 12-3

Mutations=________________________ A.---Kinds of Mutations 1) ________________________________-changes in a single gene _____________________________________-changes in 1 or a few nucleotides-@ a single point in DNA-includes substitutions,insertions and deletionsSubstitutions usually affect no more than 1 amino acid____________________________________-insertions or deletions where the reading frame of the codon message is changed-can VERY much alter or even stop the function of a protein Changes in genetic material Point mutation Frameshift mutation Gene mutation

2)Chromosomal Mutations-change in the # or structure of chromosomes-can change the location of genes on chromosomes and /or number of copies of some genes. 4 types -1)Deletions-loss of all or part of a chromosome2)__________________-extra copies of a part of a chromosome3)________________reverse directions of parts of chromosomes4)____________-part of one chromosome breaks off and attaches to another duplication inversions translocations

Substitution Insertion Deletion Gene Mutations: Substitution, Insertion, and Deletion Section 12-4

Deletion Duplication Inversion Translocation Figure 12–20 Chromosomal Mutations Section 12-4

B. Significance of Mutations Many have no effect Harmful effects include genetic disorders and cancer ________________________-contains extra set of chromosomes-bad in most cases but often helpful in PLANTS. polyploidy

V. Gene Regulation Only a fraction of a gene expressed at one time ___________________-group of genes that operate together ________________-where repressor binds operon (when it)is turned off Operons not usually found in eukaryotes-these genes are usually controlled individually and regulation more complex---mainly because of cell specializationHox genes-control differentiation of cells and tissues in the embryo operon operator

Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription Typical Gene Structure Section 12-5

Karyotypes