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Yeast are single-celled eukaryotic organisms that grow in culture as either haploids or diploids. Diploid yeast are generated when two haploid strains fuse together. Seven haploid strains of yeast exhibit similar growth habit: At
Describe the nature of the mutation affecting each of these mutant yeast strains. Explain why strains B and G display different growth habit at
How many different genes are mutated among these seven yeast strains? Identify the strains that represent each gene mutation.
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Genetic Analysis: An Integrated Approach (3rd Edition)
- The intermediates A, B, C, D, E, and F all occur in the same biochemical pathway G is the product of the pathway, and mutations 1 through 7 are all G –, meaning that they cannot produce substance G. The following table shows which intermediates will promote growth in each of the mutants. Arrange the intermediates in order of their occurrence in the pathway at which each mutant strain is blocked. A “+” in the table indicates that the strain will grow if given that substance, an “o” means lack of growth.arrow_forwardFor a haploid fungus, the starting point in the biosynthesis of the amino acid arginine is Compound X, which is always present in and absorbed from the environment. The arginine biosynthetic pathway is: Enzyme A Enzyme B Enzyme Ç Compound X It is know that genes encoding enzymes A and C are on two different chromosomes. Compound Y Compound Z- Arginine A mutant strain of genotype a (lacking only enzyme A) is crossed to a mutant strain of genotype c (lacking only enzyme C) to generate a diploid strain. Sporulation (i.e. meiosis) is subsequently induced in the resulting diploid strain. What proportion of the spores (haploids formed by sporulation) is expected to grow on medium without arginine but supplemented with Compound Y? O 100% 50% 0% 25%arrow_forwardIn E. coli, four Hfr strains donate the following markers,shown in the order donated:Strain 1: M Z X W CStrain 2: L A N C WStrain 3: A L B R UStrain 4: Z M U R BAll these Hfr strains are derived from the same F+ strain.What is the order of these markers on the circularchromosome of the original F+?arrow_forward
- A series of Hfr strains that have genotype m+ n+ o+ p+ q+ r+ are mixed with an F− strain that has genotype m− n− o− p− q− r−. Conjugation is interrupted at regular intervals and the order of the appearance of genes from the Hfr strain is determined in the recipient cells. The order of gene transfer for each Hfr strain is What is the order of genes on the circular bacterial chromosome? For each Hfr strain, give the location of the F factor in the chromosome and its polarity. Hfr5 m+ q+ p+ n+ r+ o+ Hfr4 n+ r+ o+ m+ q+ p+ Hfr1 o+ m+ q+ p+ n+ r+ Hfr9 q+ m+ o+ r+ n+ p+arrow_forwardYou have isolated 8 mutants in yeast that fail to grow on minimal media plates but do grow when they are supplemented with Arginine. You know that Arginine is synthesized in a biochemical pathway within wild-type yeast, but you do not know how many gene products it takes for the pathway. You have all of the lines as both a and a cells and mate each strain to each other in pairwise crosses and plate them on minimal media to see if they grow. You obtain the following results with (+) representing growth, and (-) indicating no growth: a 1 5 1 a 4 5 6 7 8 How many genes are represented? O 1 3 7 O Cannot tell from the data a + + + + + • + + i 0 +, + + + • + + 7 + + + + + , . + + + + + m + + + + + + + 2 + + + + + i + -I + + . . + + +arrow_forwardYou have a strain of Neurospora that is unable to synthesize histidine and thus requires H in the media in order to grow. You have isolated one revertant colony. Predict the expected proportion of the progeny that would be h+ if you cross the colony with the original mutant colony and the reversion occurred by each of the following mechanisms: Precise change of the mutated base back to its original base. A suppressor gene is mutated on a different chromosome A suppressor gene is mutated on the same chromosome but 10mu distant from the mutated gene. The mutant colony is crossed to a wild-type Neurospora colony and the following data are collected. 95% of all asci scored are h+ but 5% are h-. Which mechanism in part a is consistent with these data? Explain why and what has happened on a molecular level.arrow_forward
- Assume that a series of compounds has been discovered in Neurospora. Compounds A–F appear to be intermediates in a biochemical pathway. Conversion of one intermediate to the next is controlled by enzymes that are encoded by genes. Several mutations in these genes have been identified and Neurospora strains 1–4 each contain a single mutation. Strains 1–4 are grown on minimal media supplemented with one of the compounds A–F. The ability of each strain to grow when supplemented with different compounds is shown in the table (+ = growth; o = no growth). Which biochemical pathway fits the data presented? Media Supplement Strain A B C D E F 1 o o o + + + 2 o o o o + + 3 o o o o + o 4 o o + + + + A) A → B → C → D → E → F B) A → B → C → F → D → E C) F → B → C → D → A → E D) A → B → C → D → F → E E) A → B → F → E → C → Darrow_forwardFive independently isolated mutants of yeast all of which are unable to grow in the absence of histidine (his-) were isolated. Each mutant was crossed with all the others. The experimental results of this experiment, using + to indicate growth or 0 to indicate no growth are given below. mutant 1 13 14 15. List the members of each How many genes are definecarrow_forward18) Based on your knowledge of lactose system in prokaryotes) and considering the following genotypes, complete the table below indicating a "+" where an enzyme is produced and a where no enzyme is produced. Note: Is is a mutant that cannot recognize allolactosearrow_forward
- Brenner’s m mutant phages (m1–m6) described inFig. 8.8 were suppressed when grown in suppressor(su−) mutant bacteria; they produced full-length Mproteins that functioned like wild-type M protein.a. What gene do you think was mutant in the su−bacteria?b. When the m− phages were propagated in the su−bacterial strain, not all of the proteins made by themutant m alleles were identical to wild-type Mprotein. How did some of them differ?arrow_forwardA shuttle vector is a vector (usually a plasmid) constructed so that it can propagate in two different host species. One of the most common types of shuttle vectors is the yeast shuttle vector. Examples of such vectors derived from yeast are Yeast Episomal Plasmid (YEp), Yeast Integrating Plasmid (YIp) and Yeast Replicating Plasmid (YRp). Among these three vectors, YIp has the lowest transformation frequency and copy number per cell. Explain why Ylp is still popularly used despite its limitations.arrow_forwardAn interrupted mating study is carried out on Hfr strains 1, 2, and 3. After conjugation is established, a small sample of the mixture is collected every minute for 20 minutes to determine the distance between the genes on the chromosome. Times of entry for each of the three Hfr strains studied in the interrupted mating are provided in parenthesis. The total duration of conjugation (in minutes) is given for each transferred gene. Hfr Strain Genes Transferred Hfr 1 oriT(0) met(2) ala(8) lac(13) gal(17) Hfr 2 oriT(0) met(2) leu(7) thr(10) azi(17) Hfr 3 oriT (0) gal(3) pro(8) trp(14) azi(19) Hfr 4 oriT leu met ala lac Hfr 5 oriT trp azi thr leu a. Use the data to construct a circular map of the bacterium.arrow_forward
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