* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch. 10- Structure and Analysis of DNA and RNA p. 262-288
Genomic library wikipedia , lookup
Genetic testing wikipedia , lookup
Mitochondrial DNA wikipedia , lookup
Frameshift mutation wikipedia , lookup
Cancer epigenetics wikipedia , lookup
DNA polymerase wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Bisulfite sequencing wikipedia , lookup
RNA silencing wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
Genealogical DNA test wikipedia , lookup
DNA vaccination wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Epigenomics wikipedia , lookup
Molecular cloning wikipedia , lookup
Genetic code wikipedia , lookup
Epitranscriptome wikipedia , lookup
Helitron (biology) wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
Non-coding RNA wikipedia , lookup
Genetic engineering wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Point mutation wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Nucleic acid tertiary structure wikipedia , lookup
DNA supercoil wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Nucleic acid double helix wikipedia , lookup
Non-coding DNA wikipedia , lookup
History of RNA biology wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Microevolution wikipedia , lookup
Primary transcript wikipedia , lookup
History of genetic engineering wikipedia , lookup
Name: __________________________ Date: _________________ Hour: _____________ Ch. 10- Structure and Analysis of DNA and RNA p. 262-288 1. The functions attributed to genetic material are replication, expression, storage, and mutation. What does each of these terms mean? (p. 263) Replication: one facet of the cell cycle, a fundamental property of all living organisms. Once genetic material is replicated, it is divided equally into daughter cells. During gamete formation, the genetic material is also replicated, but each cell only gets half the original genetic material. Expression: complex process; the basis for the concept of information flow within the cell. First- transcription of DNA, resulting in the synthesis of three types of RNA- mRNA (translated into proteins), tRNA, rRNA. Translation occurs in conjunction with rRNA- containing ribosomes and involving tRNA, which acts as an adaptor to convert the chemical information in mRNA to the amino acids making up the proteins. Storage: genetic information that is present as a repository of all hereditary characteristics of an organism (information may or may not be expressed). Cells contain a complete complement of DNA, at any given point they express only part of this genetic potential. Mutation: (variability) genetic material is the source of newly arising “variability” among organisms through the process of mutation (a change in the chemical composition of DNA). If a mutation occurs, the alteration will be reflected during transcription and translation, often affecting the specified protein. If a mutation is present in gametes, it will be passed to future generations and, with time, may become distributed in the population. Genetic variation (including the rearrangement between and within chromosomes) provides the raw material for the process of evolution. 2. Contrast the various contributions made to an understanding of transformation by Griffith, by Avery, and his coworkers, and by Taylor. (p. 264-268) Griffith- Critical experiment involved an injection into mice of living IIR cells combined with heat-killed IIIS cells. Neither cells type caused the death in mice when injected alone, so Griffith expected that the double injection would not kill them either. After five days all the mice were dead. Analysis of the blood revealed large numbers of the living type IIIS bacteria! Based on the control, he knew that a mutation had not occurred- some type of interaction between the living IIR and heat-killed IIIS must have happened- he called this phenomenon transformation. He suggested that the transforming principle might be some part of the polysaccharide (carbohydrate) capsule or some compound required for capsule synthesis, but it was not the capsule alone. Griffith’s work led other physicians and bacteriologists to research the phenomenon of transformation. Avery- (with MacLeod and McCarty)- published work in what is now regarded the classic paper in the field of molecular genetics. They reported that they had obtained the transforming principle in a purified state, and that beyond reasonable doubt; the molecule responsible for transformation was DNA. They used large quantity of IIIS virulent that were centrifuged, heat-killed, and homogenized. To solidify their findings, they sought to eliminate all probable contaminants from their final product. After treatments the transforming activity still remained. Chemical testing of the final product gave strong positive reactions for DNA. Their final experiment involved experiments using crude samples of DNA- digesting enzyme deoxyribonuclease. Digestion with this was shown to destroy transforming activity leaving little doubt that the active transforming principle was DNA. Taylor: isolated an extremely rough (ER) mutant strain from a rough (R) strain. This ER strain produced colonies that were more irregular then the R strain. The DNA from the R accomplished the transformation of ER to R. The R strain was shown to also to be able to serve as the DNA donor in transformation. 3. What observations are consistent with the conclusion that DNA serves as the genetic material in eukaryotes? List and discuss them. (p. 271-272) 1. Distribution of DNA- aside from the nucleus, DNA is found in chloroplasts and mitochondria which perform genetic functions. A close correlation exists between the amount of DNA and the number of sets of chromosomes. No such correlation can be observed between gametes and diploid cells for proteins- providing circumstantial evidence favoring DNA over proteins as the genetic material for eukaryotes. 2. Mutagenesis- (Indirect evidence) UV light is capable of inducing mutations in the genetic material. Bacteria can be irradiated with various wavelengths of UV light and the effectiveness of each wavelength is measure by the number of mutations it induces. Both DNA and RNA absorb UV light most strongly at 260 nm which is also the most mutagenic wavelength. Protein most strongly absorbs at 280 nm, but no significant mutagenic effects are observed at this wavelength. 3. Eukaryotic Data- strongest evidence has been provided by the application of molecular analysis referred to as recombinant DNA technology. Segments of eukaryotic DNa corresponding to specific genes are isolated and literally spliced into bacterial DNA. Such a complex is inserted into a bacterial cell and its genetic expression is monitored. If a eukaryotic gene is introduced, the presence of the corresponding eukaryotic protein product demonstrates directly that this DNA is not only present, but functional in a bacterial cell. 4. What are the exceptions to the general rule that DNA is the genetic material of all organisms? What evidence supports these exceptions? (p. 272-273) Some viruses contain an RNA core rather than once composed of DNA. In these viruses, it would appear that RNA might serve as the genetic material- an exception to the general rule that DNA performs this function. This was demonstrated that when purified RNA from tobacco mosaic virus (TMV) was spread on tobacco leaves, the characteristic lesions caused by TMV would appear later on the leaves. It was concluded that RNA is the genetic material of this virus. 5. Describe the chemical structure of the three components of a nucleotide. What are the two types of nitrogenous bases? What is different about the pentose sugars of RNA and DNA? (p. 274) Nucleotides are the building blocks of all nucleic acid molecules. These structural units consist of three essential components: a nitrogenous base, a pentose sugar, and a phosphate group. There are two types of nitrogenous bases: purines (nine-membered double-ringed) and pyrimidines (six-membered single ring). The pentose sugars found in nucleic acids give them their names. Ribonucleic acids (RNA) contain ribose, while deoxyribonucleic acids (DNA) contain deoxyribose. Deoxyribose is missing one hydroxyl group at the C-2’ position compared with ribose. The presences of a hydroxyl group at C-2’ position distinguishes RNA from DNA. 6. Describe the various characteristics of the Watson-Crick double-helix model for DNA. (p. 278-283) 1. Two long polynucleotide chains are coiled around a central axis, forming a right-handed double helix. 2. The two chains are antiparallel that is, their C-5’- toC-3’ orientations run in opposite directions. 3. The bases of both chains are flat structures, lying perpendicular to the axis; they are “stacked” on one another, 3.4 Å (0.34 nm) apart, and are located on the inside of the structure. 4. The nitrogenous bases of opposite chains are paired to one another as the result of the formation of hydrogen bonds; in DNA, on A-T and G-C pairs are allowed. 5. Each complete turn of the helix is 34 Å (3.4 nm) long; thus, 10 bases exist in each chain per turn. 6. In any segment of the molecule, alternating larger major grooves and smaller minor grooves are apparent along the axis. 7. The double helix measures 20 Å (2.0 nm) in diameter. 7. List the three main differences between DNA and RNA. 1. RNA also has as its building blocks nucleotides linked into polynucleotide chains, the sugar ribose replaces deoxyribose and the nitrogenous base uracil replaces thymine. 2. Most RNA is usually considered to be single strandedhowever they sometimes fold back on themselves to form double-stranded regions following their synthesis. Some animal viruses that have RNA as their genetic material contain it in the form of a double stranded helix. 3. Size and sedimentation behavior in a centrifuge classify RNA. DNA stores the genetic information; RNA functions in the expression of that information. 8. What are the three types of RNA molecules? How is each related to the concept of information flow? (p. 283- 285) 1. Ribosomal RNA (rRNA)- largest of the molecules- constitutes 80% of RNA in a cell. They are important structural components of ribosomes, which function as a nonspecific workbench during the synthesis of proteins during translation. 2. Messenger RNA (mRNA)- carry genetic information from the DNA of the gene to the ribosome, where translation occurs. 3. Transfer RNA (tRNA)- smallest class of RNA- carry amino acids to the ribosome during translation. 9. What component of the nucleotide is responsible for the absorption of ultraviolet light? How is this technique important in the analysis of nucleic acids? (p. 285) UV light and the ring systems of the purines and pyrimidines interact. Any molecule containing a nitrogenous base can be analyzed using UV light. It is important in the localization, isolation, and characterization of nucleic acids. IT is used in conjunction with standard procedures that separate molecules. 10. What is the basis for determining base composition using density gradient centrifugation? (p. 285-287) The mixture can be loaded on top of a solution prepared so that a concentration gradient has been formed from top to bottom. A density gradient is created that overlaps the densities of the individual components of a mixture of molecules (usually a heavy metal salt). During centrifugation the molecules migrate until they reach a point of neutral buoyant density- the force on them is equal and opposite to the upward diffusion force and no more migration occurs. If DNAs of different densities are used, they will separate as the molecules of each density reach equilibrium. The gradient may be fractionated and the components isolated. This technique provides high resolution in separating mixtures of molecules varying only slightly in density. 11. What is the physical state of DNA following denaturation? (p. 287-288) The hydrogen bonds of the duplex structure break, the duplex unwinds, and the strands separate.