test2pluskey(mary)

test2pluskey(mary) - GENE'I'ICS I1 Exam(nro325...

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. , , GENE'I'ICS (nro 325) I~AI,~"B~ '* ,Ci - *. . . 'A I1 Exam 1U126104 (11:OO - 12:15 PM) Total @ints: 100 'w ., - 'There are 20 questions in this exam. Each qnestion carries 5 points. Answer a11 20 questioos for a maximum of 100 points. -.- - I. 'The genes A, B, G, H, 1, and T were tested in all possiblc pairs for cotransduction using the generalized transducing phage PI. Only the following pairs of genes were found to be cotransduced: G and H; G and 1,T and A, 1 and B, A and 11. What 1s the order of these genes on the chron~osnme? ti 2. Which of the following dascribes the relationship between Hfi strains and F' strains? (a) An Hfr strain donates DNA to an F strain, thus converting it into an strain. (b) After DNA is Isansferred from an Hfr toan F, the Hfi strain becomes an strain. , < When an Hfr strain is ~isctl for transdwtion, it is called an strain. ljfi strains can beconverted into F' strains through the liberation of the F @ factor and some flank~ng bacterial DNA from the b!cterial chromoso~nc. 3. sfr StrS strain that transfers genes in alphabetical order + +t tll a b c ...... x y z with a' transferred early and z' a tenninal marker, is mated with i St< cells. The mating mixture is agitated violently 15 minutes after mixigto'break apart F conjugating cells and then plated on a medium that lacks nutrient,Z and contains streptomycin. The yield of 2' S{f colonies in this mating is about one per lo7 HfS cells. There are two possible modes of origin of cells with the genotype i Str'. One possibility is that the zi Str' colony originated by a reverse mutation of i to zt in the F recipient. What is the other mode of origin of cells with the genotype Stf? Explain. z+ 5?pr (b) How can the cells that arise by these two dZYerent modes be distinguished?
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4. 111 a generalized transtiustion experimcnt, phages arc collected from an E..i.~li donor strain of genotype cvs' leti' tllr' and uscd to transduce a recipient 01 genotypes cys leu- thf. Initially, the treated recipient popu<~tio$is plated on a rnini~nal rncdinrn supplemented with leucine and threoirihc? :M&) colo,nj&s are , , -. . .,. , obtained. ' i (a) Mihat are thc possible gemiypes of these coloni&4 . 4 $\ . .." . . %. , , (b) lhese colomes are then repllca plated onto three different mcdia: - minimal plus threonine or& - m~nimal plus leucine only rn~rnmal medium What genoty-pes could, in theoy, grow on these three mcdia? 5. In two isolates (one is resistant to ampicillin and the other is sensitive to . ._.I. .'. .- . ampicillin) of a new bacterium, you find that genes encoding ampicillin resistance are being transferred into the ampicillin sensitive strain. To determine if the transfer of the ampicillin resistance gene to the sensj_tive.strain is by transduction or transformation, treat the mixed culture of cells with DNase (an enzyme that degrades DNA). How would addition of DNase into the mixed culture allow you toadistinguish between these two modes of gene transfer?
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6. 'To detem~ine the order of eight gales in E coli, conjugalion experimerlts were conducted using three different prototrophic Hfr strains yji&9:i$cipient strain of genotype rnct'arg-pkg trp. lys-his' thy leu-. Matings .
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test2pluskey(mary) - GENE'I'ICS I1 Exam(nro325...

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