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Concept explainers
When the interrupted mating technique was used with five different strains of Hfr bacteria, the following orders of gene entry and recombination were observed. On the basis of these data, draw a map of the bacterial chromosome. Do the data support the concept of circularity?
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To draw: A map for bacterial chromosome.
Introduction: The bacterial chromosome is transferred during the process of conjugation, which leads to genetic recombination. The genetic recombination provides data for mapping.
Answer to Problem 1NST
Pictorial representation: The sequence of genes are arranged as contigs, and their overlapping is shown in fig 1.
Fig 1: Overlapping of the contigs of the Hfr strains.
Pictorial representation: The chromosomal map of bacteria
Explanation of Solution
The transfer of chromosome is strain specific. It also depends on where and in which orientation in the chromosomes the F factor has integrated.
In interrupted mating, there is difference in the time of gene transfer. Some may be transferred earlier while other are transferred late. In strain 2 and 4, the common sequence is MB. In strain 1 and 3, CHRO is common, and HRO is the repetitive sequence.
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To determine: Whether the given data support the concept of circularity.
Introduction: A single bacterial chromosome contains most of the DNA of the bacteria. Mapping the bacterial chromosomes provides information regarding the position of various genes.
Explanation of Solution
Contigs are the continuous set of overlapping DNA segments. These segments represent a particular region of the DNA. In the given figure, the end overlaps each other. In two strains the order is reversed which means the orientation of the transfer is reversed. By the overlapping of the contigs in the given strains, the map that will be constructed is TCHROMBAK. All the genes are linked together to give a map. The ends overlap indicates that the map is circular. When all these chromosomes are arranged in the form of a map, they form a circular map.
Thus, the map constructed that will be constructed from the given Hfr strains is TCHROMBAK. The overlap ends indicate that the map is circular.
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Chapter 6 Solutions
Concepts of Genetics (11th Edition)
- DNA from a strain of Bacillus subtilis with genotype a + b + c + d + e + is used to transform a strain with genotype a – b – c – d – e – . Pairs of genes are checked for co-transformation and results shown below are obtained. Based on these results, what is the order of the genes on the bacterial chromosome? Show how you work out the order by diagraming.arrow_forwardneed helparrow_forwardAn Hfr strain that is hisE + and pheA + was conjugated to a strain that is hisE − and pheA −. The conjugation was interrupted at different times, and the percentage of recombinants for each gene was determined by streaking on media that lacked either histidine or phenylalanine. The following results were obtained: A. Determine the map distance (in minutes) between these twogenes.B. In a previous experiment, it was found that hisE is 4 minutesaway from pabB and that PheA is 17 minutes from pabB. Drawa genetic map showing the locations of all three genes.arrow_forward
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- An Hfr strain that is leuA+ and thiL+ was mixed with a strain thatis leuA− and thiL−. In the data points shown in the following graph,the conjugation was interrupted at different time points, and thepercentage of recombinants for each gene was determined bystreaking on a medium that lacked either leucine or thiamine.Make a calculation.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_forwardDNA from a strain of Bacillus subtilis with genotype a+ b+ c+ d+ e+ is used to transform a strain with genotype a– b– c– d– e–. Pairs of genes are checked for co-transformation and results shown below are obtained. Based on these results, what is the order of the genes on the bacterial chromosome? please show how you worked out the order by diagraming, thank you! Pair of genes Co-transformation a+ and b+ no a+ and c+ no a+ and d+ yes a+ and e+ yes b+ and c+ yes b+ and d+ no b+ and e+ no c+ and d+ no c+ and e+ yes d+ and e+ noarrow_forward
- Determine the coefficient of coincidence and the interferencearrow_forwardF ′strains in E. coli are derived from Hfr strains. In some cases, these F ′strains show a high rate of integration back into the bacterial chromosome of a second strain. Furthermore, the site of integration is often the site occupied by the sex factor in the original Hfr strain (before production of the F ′strains). Explain these results.arrow_forwardThree different Hfr donor strains are mixed with separate samples of an F strain, and the following mapping data are provided from studies of interrupted conjugation: Appearance of genes in F cells Hfr1: Genes b* d* c* f* g* Time* 3 16 27 59 Hfr2: Genes e* f* c* d* b+ Time 6 24 35 46 48 Hfr3: Genes d* c* f* e+ g* Time 4 15 26 44 58 Construct a genetic map for these genes, indicating their order on the bacterial chromosome and the distances between them.arrow_forward
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