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DNA and RNA Chapter 12 -1
GENETIC MATERIAL In the middle of the 1900’s scientists were asking questions about genes. What is a gene made of? How do genes work? How do genes determine characteristics of organisms?
DO PROTEINS CARRY THE GENETIC CODE? At the time most scientists believed proteins that _____ had to be the molecules that made up genes. There were so many different kinds proteins and DNA seemed to be too monotonous. . . repeating the same 4 subunits. ___
GRIFFITH’s EXPERIMENT 1928 – Frederick Griffith looked at pneumonia bacteria trying to figure out what made people die S (SMOOTH) strain - killed mice R (Rough) strain -mice lived
If he heated the LETHAL strain first the mice lived. ________ The heat killed the bacteria and they were no longer LETHAL.
BUT. . . If he mixed heat-killed LETHAL bacteria with live harmless bacteria the mice DIED ! ________ When he looked inside dead mice, he found LIVE LETHAL _______ bacteria! Somehow the heat killed LETHAL bacteria passed their characteristics to the harmless bacteria.
Griffith called this process TRANSFORMATION _________ because one strain of bacteria had been changed permanently into another. But what was the factor that caused the transformation? A protein ? A lipid ? A carbohydrate ? A nucleic acid ?
http: //en. wikipedia. org/wiki/Oswald_Avery 1944 Oswald Avery’s team of scientists repeat Griffith’s experiments looking for the transforming molecule. After heat killing the LETHAL Pneumonia bacteria, he treated them with digestive enzymes that destroy specific kinds of molecules. If proteins, polysaccharides, lipids, or RNA’s were destroyed. . . Transformation still occurred! _______________ http: //cystitis-cystitis. com/Images/testtube. jpg http: //faculty. uca. edu/~johnc/mbi 1440. htm
But when they treated the heat-killed LETHAL bacteria with enzymes to DNA there was NO destroy _____ transformation!. . . the mice lived! DNA was the molecule that caused the genetic change. http: //web. jjay. cuny. edu/~acarpi/NSC/12 -dna. htm
GRIFFITH EXPERIMENT (PNEUMONIA-RAT) Showed genetic ______ material could be passed between bacteria & cause a change. AVERY EXPERIMENT (Digestive enzymes) showed that the genetic material DNA was _____
Scientists are skeptical… it takes more than one experiment to convince them. 1952 -Alfred Hershey and Martha Chase experimented with viruses that infect bacteriophages bacteria = _________ Knew bacteriophages were made of proteins and _______ DNA ____ Hear about their cool experiment
BACTERIAL VIRUSES http: //faculty. uca. edu/~johnc/mbi 1440. htm
http: //www. mun. ca/biology/scarr/hersheychase-experiment. jpg
HERSHEY-CHASE BLENDER EXPERIMENT only DNA not protein Showed________ entered cell during infection. Conclusion Genetic material in virus was DNA _____________ NOT protein
DNA is a DOUBLE HELIX http: //www. time. com/time 100/scientist/profile/watsoncrick. html http: //en. wikipedia. org/wiki/Rosalind_Franklin X-ray experiments by Rosalind Franklin led James Watson and Francis Crick to the discovery of the structure of DNA in 1953
Section 12 -1 Figure 12– 7 Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
NUCLEIC ACIDS are built from subunits called NUCLEOTIDES __________ Image by: Riedell SUGAR in DNA is ________ deoxyribose
NITROGEN BASES in DNA _______= A ADENINE _______ =G GUANINE _______ CYTOSINE = C _______ THYMINE = T No URACIL
DEOXYRIBONUCLEIC ACID DOUBLE _______ STRANDED Image from: http: //www. tokyo-med. ac. jp/genet/picts/dna. jpg Backbone (sides of ladder) made of PHOSPHATES _______ and sugars _______
Nitrogen bases =“Steps of ladder” A Phosphate group G Deoxyribose sugar C T Purines (2 rings) Pyrimidines (1 ring) © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
CHARGAFF’S RULES A = T G = C _________ At time no one knew why… now we know its because Adenine always bonds THYMINE across with______ Guanine always bonds CYTOSINE across with ______ Image from: http: //evolution. berkeley. edu/evosite/evo 101/images/dna_bases. gif
DOUBLE HELIX Hydrogen _______ bonds between nitrogen bases hold the two strands together. Image from: http: //evolution. berkeley. edu/evosite/evo 101/images/dna_bases. gif
Interest Grabber 12 -2 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.
Interest Grabber Answers 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? Lines will likely look similar. 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? Overlaying the papers will show variations in the lines. 4. How could you use the original paper to draw exact copies of the line without tracing it? st Use 1 line as a template to draw the line on another sheet of paper. 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original? Each cell must have the correct DNA, or the cell will not have the correct characteristics.
CHROMOSOMES & DNA REPLICATION 12 -2
Chromosome Structure in Prokaryotes Approximately 5 million base pairs 3, 000 genes Chromosome E. coli bacterium Bases on the chromosome DNA molecule in bacteria is: SINGLE _______ CIRCULAR _______ CYTOPLASM (NO nucleus) Found in _____ © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
DNA in EUKARYOTES is packaged into chromosomes http: //www. paternityexperts. com/images/DNA-of-life. jpg Humans have approximately 3 billion base pairs (1 m long) 60, 000 to 100, 000 genes If the diameter of the DNA (2 nanometers) was as wide as a fishing line (0. 5 millimeters) it might stretch as far as 21. 2 km (or 13. 6 miles) in length which would all have to be packed into a nucleus, the equivalent size of 25 cm in diameter. That is some packaging!
THINK ABOUT IT How could you get This piece of string into the container? http: //www. artzooks. com/files/3966/AZ 533823_320. jpg
Chromosome Structure of Eukaryotes © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved Chromosome Nucleosome DNA double helix Coils Supercoils DNA is: multiple _______ in chromosome bundles _______ Found in _____ nucleus Histones
Chromosome Structure of Eukaryotes © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved Eukaryotic chromosomes are Nucleosome made of PROTEINS DNA _____ & _____ (called ______) HISTONES Together the DNA & histone protein forms a bead-like NUCLEOSOME structure called a _______ Histones DNA double helix
© Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved Chromosome Structure of Eukaryotes Nucleosome Chromosome DNA double helix Coils Supercoils Histones Nucleosomes pack together to form thick coiled fibers. When cell is NOT dividing, these fibers are spread out in nucleus as CHROMATIN (Allows reading of code) ______.
Chromosome Structure of Eukaryotes © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved Chromosome Nucleosome DNA double helix Coils Supercoils Histones When cell gets ready to divide, the fibers pack even more tightly to form chromosomes ______. (Makes it easier to move DNA during mitosis)
Image from: http: //evolution. berkeley. edu/evosite/evo 101/images/dna_bases. gif HOW IS DNA COPIED? The structure of DNA explains how it can be copied. Each strand has all the info needed to construct matching the _____other half. If strands are separated, base-pairing rules allow _______ you to fill in the complementary bases.
Figure 12– 11 DNA Replication Section 12 -2 New strand Original strand DNA polymerase Growth Replication fork Nitrogenous bases Replication fork New strand Original strand Sites where strand separation and replication forks replication occur are called _______
REPLICATION STEPS 1. Enzymes “unzip” molecule by breaking ________ Hydrogen bonds that hold the strands together and unwind it. DNA polymerase joins nucleotides 2. ________ using original strand as template and spell checks _______for errors. opposite directions 3. Copying happens in ____ along the two strands & in _____ multiple places at once.
See a video clip about DNA REPLICATION (12 B)
Section 12 -3 Interest Grabber Information, Please DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out.
Interest Grabber 1. Why do you think the library holds some books for reference only? Possible answers: The books are too valuable to risk loss or damage to them. The library wants to make sure the information is always available and not tied up by one person. 2. If you can’t borrow a book, how can you take home the information in it? Students may suggest making a photocopy or taking notes. 3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell? Students will likely say that the cell has some way to copy the information without damaging the DNA.
RNA and PROTEIN SYNTHESIS 12 -3 © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
RNA- the Other Nucleic Acid NUCLEOTIDES Also made of ______ RIBOSE instead Sugar is _______ of deoxyribose. SINGLE stranded RNA is _____ URACIL Contains _____ instead of thymine. http: //images 2. clinicaltools. com/images/gene/dna_versus_rna_reversed. jpg
3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS RIBOSOMAL _________RNA (r. RNA) Combines with proteins to form ribosomes TRANSFER _________RNA (t. RNA) Matches m-RNA codon to add correct amino acids during protein synthesis _________RNA (m. RNA) MESSENGER carries code from DNA to ribosomes r. RNA and t-RNA images from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved m. RNA image from http: //wps. prenhall. com/wps/media/tmp/labeling/1140654_dyn. gif
Section 12 -3 Figure 12– 14 Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase RNA DNA RNA POLYMERASE Enzyme called ___________ separates strands, then uses one strand as a template to assemble an RNA copy.
How does RNA POLYMERASE know where a gene starts and stops? Enzyme binds to places with specific DNA PROMOTERS sequences called ________. RNA POLYMERASE PROMOTERS tell _________ where to start. Signals at the end of the gene code cause transcription to _____ stop. http: //images 2. clinicaltools. com/images/gene/dna_versus_rna_reversed. jpg
Video 3 See another transcription movie See a video clip about TRANSCRIPTION (12 D)
RNA’s require EDITING before use Image by Riedell
WHY WASTE IT? Why spend energy making a large RNA and then throw parts away? May allow same gene to be used in different ways in different kinds of cells. May have a role in evolution… allows small changes in genes to have a big effect.
DNA MASTER PLAN stays safe in nucleus © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved TRANSCRIPTION (DNA→ RNA) & PROCESSING takes place in nucleus TRANSLATION (RNA→ proteins) takes place on ribosomes in cytoplasm “Blueprints” of master plan are carried to building site http: //www. home-improvement-resource. com/images/architect. jpg
HOW CAN JUST 4 BASES GIVE DIRECTIONS TO MAKE 20 AMINO ACIDS? CODON Message is read in groups of 3 = _____ UCGCACGGU UCG-CAC-GGU Serine - Histidine - Glycine Codons represent different amino acids
The m-RNA Code Section 12 -3 64 possible codons Some amino acids have more than one codon. AUG START= _______ STOP 3 codons for _____
ANTICODON ______ on t. RNA EACH t. RNA carries only one kind of amino acid _______ matches up with CODON ____ on m. RNA Images modified from © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
Section 12 -3 Figure 12– 18 Translation
Section 12 -3 Figure 12– 18 Translation (continued)
Video 4 SEE ANOTHER Translation Animation See a video clip about PROTEIN SYNTHESIS (12 D) Video 4
Mendel/flower images from: http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Book. TOC. html Blood cell by Riedell GENES & PROTEINS Proteins are the connection between the gene code in the DNA and how that gene is expressed. A gene that codes for an enzyme (protein) to make a pigment can control the color of a flower. A gene that codes for an enzyme (protein) adds carbohydrates to glycoproteins to produce your blood type. Enzymes catalyze and regulate chemical reactions so proteins build and operate all cell components.
REPLICATION DNA → DNA ______ TRANSCRIPTION DNA → RNA ______ RNA→ Protein TRANSLATION ______
Concept Map Section 12 -3 can be also called which functions to from also called to which functions to to make up also called which functions to
Concept Map Section 12 -3 RNA can be Messenger RNA also called Ribosomal RNA which functions to m. RNA also called which functions to r. RNA holds t. RNA to m. RNA Carry instructions from DNA to Ribosome to make up Polypeptides (amino acid chans) Transfer RNA also called which functions to t. RNA Bring amino acids to ribosome
MUTATIONS 12 -4
REMEMBER! MUTATIONS ________ are changes in the genetic material. Mutations can happen when cells make mistakes _______ in copying their own DNA radiation or be caused by ________ or chemicals in the enviroment. ______
KINDS OF MUTATIONS Mutations that produce changes in a single GENE MUTATIONS gene = ___________ Mutations that produce changes in whole chromosomes = ___________ CHROMOSOMAL MUTATIONS
GENE MUTATIONS One or a few Mutations involving ________ = _________ nucleotides Point mutation because they occur at a single point in the DNA sequence. TYPES OF POINT MUTATIONS: ___________ substitutions deletions ___________ insertions ___________
SUBSTITUTION Changes one base for another ATTCGAGCT ATTCTAGCT
SICKLE CELL ANEMIA CAUSE: (autosomal recessive) A changed to T (glu to val) gene on chromosome #11 that codes for part of hemoglobin protein (carries oxygen in blood)
DELETION ____________________ Piece of DNA code for one gene is lost Image from: http: //www. biology-online. org/2/8_mutations. htm
Duchenne Muscular Dystrophy CAUSE: (X linked recessive) DELETION in gene that codes for a muscle protein
Karyotype- image of all chromosomes aligned
Sex Linked Genetic Disorders These disorders are inherited from your mom or dad on their X or Y chromosome. Boys have– X Y chromosomes (X from mom, Y from dad) DAD –X Y Girls have– X X chromosomes (X from mom, X from dad) MOM X X Children: Boy Girl X Y X X
INSERTION Piece of DNA is copied too many times Image from: http: //www. biology-online. org/2/8_mutations. htm
GENE MUTATIONS Substitutions usually affect no more than a Amino acid but deletions and single ______, insertions can have a more dramatic effect. IMAGE FROM BIOLOGY by Miller and Levine; Prentice Hall Publishing© 2006
FRAME SHIFT MUTATIONS Change multiple bases in code thefatcatatetherat the fat cat ate the rat __________ INSERTION thefatcatateatetherat the fat cat att eth era t DELETION thefatcatatetherat the fat ata tet her at
FRAME SHIFTS Frame shift mutations change every Amino acid ______ in the ______ protein that follows the shift. Frame shifts can alter a protein so function much it is unable to _______
CHROMOSOMAL MUTATIONS Mutations involving changes in the Number structure _______ or _______ of whole chromosomes TYPES OF CHROMOSOMAL MUTATIONS: deletions ___________ duplications ___________ inversions ___________ translocations ___________
DELETION Piece of chromosome is lost ____________________ Image from: http: //www. biology-online. org/2/8_mutations. htm
DUPLICATION Piece of DNA is copied too many times ________________________ Image from: http: //www. biology-online. org/2/8_mutations. htm
HUNTINGTON’S • Degenerative brain disorder • Symptoms appear age 30 -40 • Lose ability to walk, think, talk, reason • Cause = ADDITION of extra CAG repeats
Similar to duplication sometimes WHOLE chromosomes can be copied. • Down Syndrome (trisomy 21)– is a genetic disorder in which a child has 3 copies of chromosome 21
INVERSION Segment flips and reads backwards Image from: http: //www. biology-online. org/2/8_mutations. htm
TRANSLOCATION Segment breaks off and joins a different non-homologous chromosome Image from: http: //www. biology-online. org/2/8_mutations. htm
MUTATIONS neutral Most mutations are ______ meaning they have little or no effect on gene ______. function defective proteins Mutations that cause ________ HARMFUL are usually ______ Harmful mutations are associated with many genetic disorders and can cause ________ cancer
MUTATIONS Mutations are also a source of Genetic variability _________ and can be beneficial _______ Can help an organism _________ Survive and reproduce variation Provide _____ in population natural selection for ______ to act upon MORE ON THIS 2 nd SEMESTER!
POLYPLOIDY Condition in which an organism has extra sets of chromosomes POLYPLOIDY = ________ LETHAL _____ in humans, but beneficial in some ______. plants 3 N or tetraploid (___) 4 N plants Triploid (___) are often ________ larger and stronger than diploid plants (2 N=Normal, 2 sets).
GENE REGULATION 12 -5 http: //www. awesomebackgrounds. com/s-energy-and-power. htm
Only a fraction of genes in a cell are expressed (made into RNA) at any given time. How does the cell decide which will be turned on and which will stay “silent”? PROMOTER You already know about _______ regions that show RNA polymerase where to start. REGULATORY SITES that There are other ___________ control whether a gene is ON or OFF.
Typical Gene Structure Section 12 -5 Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription
E. Coli lac operon See a MOVIE choose animation/narrated Group of genes that operate together are OPERON called an ________ Genes code for enzymes needed to digest lactose sugar. Only needed if glucose is not available http: //www. life. uiuc. edu/bio 100/lectures/s 97 lects/16 Gene. Control/lac_operon_ind. GIF
Most of time glucose is available so OFF by a lac operon is turned _____ REPRESSOR ______ molecule that sits on a regulatory site next to the promoter OPERATOR called the ______
What if there’s NO GLUCOSE? Cells need to get rid of the repressor ON and turn _____the lac genes to digest lactose instead. The presence of lactose causes a change in the ______ REPRESSOR molecule so so it can’t bind the operator site. Image modified from: http: //www. life. uiuc. edu/bio 100/lectures/s 97 lects/16 Gene. Control
Cells turn genes ON & OFF as needed Many genes are regulated by REPRESSOR _______ proteins that keep them turned off until needed. Others use proteins that speed up transcription ________ or affect protein synthesis __________
EUKARYOTES are more COMPLEX Additional regulatory sequences: ENHANCER regions 1. ______ upstream from promoters bind many different regulatory proteins TATA box 2. _____ (TATATA or TATAAA) helps position RNA POLYMERASE Image by Riedell
DEVELOPMENT & DIFFERENTIATION Gene regulation is also important in shaping way organisms develop How does a zygote become a multi-cellular organism? How does it know what kind of cell to be?
DEVELOPMENT & DIFFERENTIATION Cells DIFFERENTIATE ________ by turning different genes on and off. http: //www. ncu. edu. tw/~ls/graph/faculty_pictures/whole_time/SLC_lab-1. jpg BUT… How does a cell know where it is in the body? and what genes it should turn on? and when?
In the 1980 s, researchers discovered a series of genes in fruit flies called Hox genes ______ These genes control the organization of the developing embryo and tell parts where to grow and when. Mutations to Hox genes can cause a leg to grow where an antenna should sprout. http: //evolution. berkeley. edu/evosite/history/hox. shtml
Since that time, HOX genes with almost identical sequences have been found in a variety of organisms including HUMANS ______ © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
HOX GENES Similar genes controlling the eyes of insects and our own eyes have also been discovered. Our version of the gene can be inserted in a fly and still trigger the building of an insect eye! http: //evolution. berkeley. edu/evosite/history/hox. shtml
SO WHAT? The similarities between HOX gene sequences in very different organisms and the ability of these genes to trade places and still function in different species suggests that these organisms share a common ancestor _____________