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Study_question_for_lectures_1-4.doc

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Department
Biology
Course
BIOL 308
Professor
Dragana Miskovic
Semester
Fall

Description
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? [L: 1, S: 9] • The potential function of the protein of interest and how important the protein is for survival  through identification/isolation/survival of MUTANTS • The number of genes involved in certain processes • The order of these genes (proteins) in the process and their relations  by applying a genetic approach called COMPLEMENTATION ANALYSIS • The interactions between different genes (proteins)  by using genetic approach called GENETIC SUPPRESSION 2. How would you define permissive conditions in respect to temperature sensitive mutants? [L: 1, S: 7-8] • Permissive conditions: conditions under which a conditional mutant gene product can function (ex. The permissive temperature for a temperature-sensitive mutant) • Permissive conditions in respect to temperature-sensitive mutants is the temperature at which a temperature-sensitive mutant gene product takes on a normal, functional phenotype; the mutant gene product behaves normally, even though there is a mutant allele present 3. Define (or compare and contrast): a) gene expression; transcription; replication; translation; b) gene; allele [textbook/internet] a) Gene expression: the process by which gene products (RNA transcripts and proteins) are made from the instructions encoded in DNA • Includes both transcription and translation Transcription: the process by which an RNA copy of a gene is made (DNA  RNA) Replication: the process by which the DNA double helix unwinds and makes an exact copy of itself (1 DNA  2 DNA) Translation: the process by which ribosomes decode mRNA to synthesize a protein (RNA  protein) b) Gene: the basic unit of heredity; a complete chromosomal segment responsible for making a functional product Allele: one of a number of alternative forms of a given gene (or DNA sequence) that can occupy a given genetic locus (location) on a chromosome • Ex. The gene (DNA sequence) coding for eye colour has several variations (alleles), such as alleles that code for blue eyes and alleles that code for brown eyes 4. Explain by using your own words the meaning/significance of gene expression. • Gene expression: the process by which gene products (RNA transcripts and proteins) are made from the instructions encoded in DNA • This is important because many cellular processes rely on these gene products (ex. proteins); proteins can act as enzymes which catalyze biological and chemical reactions 5. What are the roles of model organisms in molecular biology studies? Choose two model organisms and explain your reasoning. [L: 1, S: 14-17, textbook pg. 229] • Model organisms are simpler models used to study more complex organisms • Model organisms are useful for medical research because they have specific characteristics that resemble a human disease or disorder • Example 1: Drosophila o Short life cycle (2 weeks) o Ease of culture (easy to maintain) o High prolificacy (females can lay up to 100 eggs/day) • Example 2: Mouse o 85% of the DNA in mice is the same as humans o Less than 1% of mouse genes have no detectable homolog in humans o Physiology is similar to that of humans (since mice are also mammals) 6. What are three main functions of DNA? Explain the importance of each of them. [L: 2, S: 7-17] 1. Stores information – information (sequence of bases) is used in coding for proteins and different RNAs, and used as regulatory signals 2. Replicates faithfully – important in the preservation of genetic information a. DNA replicates semi-conservatively, in which 2 strands of parental DNA separate and each serve as a template for synthesis of a new daughter strand b. Information is preserved since one strand predicts the sequence of the other strand 3. Has ability to mutate – important in the variability of genetic information a. Mutations can form new alleles b. Mutations in the coding sequence could result in alterations in the protein product or cause no product formation (knockout) c. Mutations in the regulatory sequence could alter regulation of expression of the product 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? [textbook pg. 20-24] • Phosphodiester bonds link adjacent nucleotides (of the same DNA strand) to form a DNA chain (bond between phosphate on the 5’ carbon of sugar and OH group at the 3’ carbon on adjacent sugar) • Hydrogen bonds form between the nitrogenous bases on opposite strands of the DNA chains; these bonds provide one type of force that holds the 2 DNA strands together • Hydrophobic interactions in the DNA structure causes the highly negative (hydrophilic) phosphate backbone to face the “outside” of the DNA structure and the non-polar (hydrophobic) bases to face the “inside” of the DNA structure 8. What noncovalent interactions are involved in maintaining the double-helical conformation of DNA? [L: 3, S: 3-6] • Hydrogen bonds – sharing of a hydrogen atom between 2 electronegative atoms (between adjacent bases on opposite DNA strands); in DNA, H-bonds between A & T, and G & C • Van der Waals interactions – a weak electrical attraction between all types of molecules (forming temporary dipoles between adjacent molecules) • Hydrophobic interactions – non-polar groups (ex. Nitrogenous bases) are hydrophobic and thus “hide” from water (causing them to aggregate to the “inside” of the DNA structure) o NOTE: H-bonds, Van der Waals, and hydrophobic interactions are individually weak; but if there are lots of them between 2 molecules, they become very strong 9. Learn to recognize nitrogenous bases (A,T,G,C,U) and respective nucleotides. [L: 3, S: 9] RULES: • Purines: 2 rings TIP: shorter word = bigger structure • Pyrimidines: 1 ring (and vice versa) • Guanine has a =O on top, adenine has a –NH 2 • Base with the O (guanine) will NOT bind to another base with the same O (uracil/thymine) 10. Describe Meselson-Stahl ex
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