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Updated SQ 1-4.doc

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University of Waterloo
BIOL 308
Dragana Miskovic

STUDY QUESTIONS: LEC 1-4 1. What information(s) could you obtain from a genetic approach of studying mutants defective in a particular process? A. Function and importance of a protein (isolation, identification, permissiveness of mutation) B. Number of genes involved in a certain process C. Location/order of the genes in the process (complementation analysis) D. Interactions between different genes by using genetic suppression. NOTE: B, C and D are carried out by the Lac Operon 2. How would you define permissive conditions in respect to temperature sensitive mutants? Permissive conditions are those under which a mutation is silenced. Eg: In temperature sensitive mutations, at low temperature (permissive conditions), the mutation will be almost silent and the organism will be able to survive. On the other hand, at higher temperatures, the organism will fail to survive due to loss of function. 3. Define: a) gene expression; transcription; replication; translation; b) gene; allele Gene Expression Transcriptio Replication Translatio n n Definitio Process by which The process The process of The n information from a of formation forming process of gene is used in the of RNA from multiple formation synthesis of a DNA by RNA copies of DNA of protein functional protein polymerase by semi- from or RNA product. conservative mRNA. replication Steps DNA replication, transcription, post- transcriptional modifications, translation and post-translational modifications Cell Mainly in S phase All phases Cycle interphase of the cell cycle Genes are sequences of nucleotides in a genome that contain information coding for the synthesis of a functional protein or RNA product. Alleles are alternative sequences of a particular gene; more specifically, two homologous chromosomes may contain different sequences of a specific gene at a particular locus, and thus contain different “alleles”. 4. Explain by using your own words the meaning/significance of gene expression. Gene expression forms the central dogma of life. Without gene expression, there would be no passing of genetic information to off springs, no formation of proteins and life will cease to exist. Moreover, all cells in an organism contain the same DNA, however, not all cells carry out the same functions. The process of gene expression is selective. Different tissue types express different proteins depending on their function. This selectivity of the gene expression helps the cell conserve energy and resources by not forming unwanted proteins and therefore, increases the viability of the cell. 5. What are the roles of model organisms in molecular biology studies? Choose two model organisms and explain your reasoning. Model organisms are used in molecular biology studies because they have many benefits, including simplicity, relative ease to use, cheapness, and often short reproductive times. They are also used as standards because so much information has been collected on them and continue to be collected. In this way, vast and specific amounts of information about these model organisms are obtained, and can be extrapolated to other organisms, including humans. For example, mice can be used to model mammalian species such as humans due to highly conserved biological pathways and processes, and they have relatively quick turnover rates compared to other similar organisms. Escherichia coli are used to model metabolic processes due to their simplicity, and the conservation of metabolic processes throughout many species. 6. What are three main functions of DNA? Explain the importance of each of them. Stores information – for the production of all proteins required for life. These instructions are then passed on to daughter cells providing them with the essential information to synthesize their own required proteins. Replicates faithfully – by a semi-conservative mechanism. The two strands separate and each is used to form a second strand. This mechanism ensures that both the parent and the new strand are exactly identical. It also ensures that if a mutation were to occur, it would only be replicated on one of the two new strands. Can mutate - The only source of variability in DNA is mutations. Mutation can lead to the formation of new alleles which if selected for by the natural selection process can result in evolution. 7. What is (are) the role(s) of phospho-diester bonds in DNA structure? What is (are) the role(s) of hydrogen bonds in DNA structure? What is (are) the role(s) of hydrophobic interactions in DNA structure? Phosphodiester bonds provide the rigid backbone for DNA structure, and also help stabilize the molecule as they are negatively charged and repel from each other, allowing H-bonding to occur between the bases instead. Hydrogen bonds in DNA structure provide minimal stabilization, but also allow for hybridization between strands due to complementary hydrogen bonding between A and T, and between G and C. Hydrophobic interactions make it favourable for DNA strands to be hybridized in order to minimize the water molecules that form the cage around the molecule – thus, provide an entropically favorable way for DNA duplex formation. 8. What noncovalent interactions are involved in maintaining the double-helical conformation of DNA? Ionic bonds, hydrogen bonds, van der Waals interactions, and hydrophobic interactions. • Ionic bonds are formed between the negatively charged phosphate groups on DNA and the positively charged ions. They help reduce the repulsion between the 2 DNA strands and therefore
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