Hfr bio+ glu+ amp^R str^S X F- bio- glu- amp^s str^r The markers are transfered
ID: 83014 • Letter: H
Question
Hfr bio+ glu+ amp^R str^S X F- bio- glu- amp^s str^r
The markers are transfered in the order given (with bio transferring first), but the first three genes are very close together. Exconjugants are plated on a medium containing str (streptomyacin to counterselect Hfrcells), amp (ampicillin), glu (glutamine) and bio (biotin). The following results are obtained for 400 colonies from thee plates isolayted and tested for growths on various media.
1) amp only 351
2) amp, glu 360
3) amp, bio 380
4) amp, glu, and bio 400
a. Write a list of genotypes and indicate the number of individuals in each.
b. calculate the recombination frequencies.
Please explain the best you can how you get to the answer!
Explanation / Answer
Hfr is the donor strain and F- s tthe recipient strain. During conjugation, the genes will get tansferred from the Hfr strain to the F- strain. After conjugation when the bacteria is plated on a minimal medium, it will grow only if it manufactures all the essential nutrients i.e biotin and glutamine. In microbiology, one colony arises from one single organism. Now, in this question they have plated the cells on the following medium:
1. amp only--> This medium only contains ampicillin. Here only those organisms will grow who manufacture biotin and glutamine and are resistant to ampicillin. Therefore, the genotype will be bio+ glu+ amp^R Str^S
351 individuals
2. amp, glu --> Only those organisms will grow who manufacture biotin, and are resistant to ampicillin. Glutamine they will use from the minimal medium which is supplemented with glutamine. Therefore, the genotype will be bio+ glu- amp^R Str^S
360 individuals
3. amp, bio --> Only those organisms will grow who manufacture glutamine and are resistant to ampicillin. They will use biotin from the minimal medium which is supplemented with biotin. Therefore, the genotype will be bio- glu+ amp^R Str^S
380 individuals
4. amp, glu and bio--> Only those organisms will grow who are resistant to ampicillin. They will use biotin and glutamine from the minimal medium which is supplemented with biotin and glutamine. Therefore, the genotype will be bio- glu- amp^R Str^S
400 individuals
Recomination frequency = (Total no. of recombinants/total no. of progeny) * 100
= (351+360)/1491 *100
=47.69%