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University of Waterloo
BIOL 308
Dragana Miskovic

Study questions for the lectures 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 of the genes in the process (Complementation analysis) d. Interactions between different genes by using genetic suppression. N.B: Remember b, c & d by 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 (or compare and contrast): a) gene expression; transcription; replication; translation; b) gene; allele a) Gene Transcription Replication Translation Expression Def Process by The process of The process of The process of which formation of forming formation of information on RNA from DNA multiple copies protein from DNA is made by RNA of DNA by mRNA. into a polymerase semi- functional gene conservative product replication (protein or mRNA) Steps DNA replication, transcription, post- transcriptional modifications, translation and post- translational modifications Cell Cycle Occurs mainly Occurs in the S Occurs in all in interphase phase of the phases of the cell cycle cell cycle b) Gene: The sequence of nucleotides that code for a particular protein or RNA. It includes the regulatory molecules involved. So in other words, it’s the entire DNA sequence required for production of a functional protein or RNA. Allele: Variants of a single gene. 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. Carrying out experiments on molecular level may not always be very feasible and the experiments are simplified by using less complex organisms and extrapolating the results to the more complicated organisms. This is done because: a. They are simple b. Inexpensive c. Short reproductive period d. Relatively small e. Easy to maintain f. There is lots of data available to aid the researcher g. The results can be extrapolated to higher organisms E.g: The mouse is used as a model for human development. The mouse shows similar genetic defects but it would be impossible to cage human beings and monitor their development and therefore, the mouse is used instead. All the above 7 factors apply as well. Yeast (Saccharomyces cervisiae) is a single celled eukaryotic cell with mutants readily available and easily induced and can therefore be used to study the effects of mutations. 6. What are three main functions of DNA? Explain the importance of each of them. a. Stores information. DNA 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. b. Replicates faithfully. DNA replicates by a semi-conservative mechanism. That is, 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 ensure that if a mutation were to occur, it would only be replicated on one of the two new strands. c. 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? Phospho-diester bonds form between the 5’ phosphate group on one sugar and the 3’ OH group on the next sugar, they form the sugar-phosphate backbone of DNA and RNA. Hydrogen bonds help in base pairing. A binds with T with 2 hydrogen bonds, C binds with G with 3 hydrogen bonds. Hydrogen bonds also help stabilize the molecule by formind hydrogen bonds with different molecules. Hydrophobic interactions are non-polar Vander Waal interactions. They are temporary and are formed by small dipole moments that occur due to the random movement and distribution of electrons. They help stabilize DNA structure by forcing the bases to join inwards away from the polar water molecules. 8. What noncovalent interactions are involved in maintaining the double- heli
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