You are studying a strain of bacteria. You that it has suddenly gained the abili

Question

You are studying a strain of bacteria. You that it has suddenly gained the ability to survive antibiotics. After asking around, you find out that your partner did not fully clean out the test tubes after growing antibiotic-resistant bacteria, and that you then used the dirty tubes. Your partner claims that couldn't be why your bacteria changed, as his bacteria had been killed in the tubes. Could your bacteria have gotten a new trait from dead bacteria? If so, how? You infect a bacterial culture with two strains of bacteriophage. One is h^+ r and the other is hr^+. You obtain the following numbers of plaques of each type. How far apart are the h and r genes? h^+ r 846 hr^+ 852 h^+ r^+ 73 hr 75 Describe how the experiments of Griffith, and later Avery MacLeod and McCarty that DNA was the genetic material?

Explanation / Answer

1. Yes, there is one possibility through which bacteria gained trait from dead bacteria. The process of transformation, in which after death or cell lysis some bacteria release their DNA into the environment, other bacteria generally of same species, can come into the contact of these fragment, take them up and incorparate into their DNA by recombination.

Genetically transformed cell called recombinant cell, that contain DNA of donar and receipent. In this experiment dead bacteria release their DNA in test tube which taken up by other bacteria and due to recombination bacteria develop capability of surviving in the presence of antibiotic.

2. To calculate distance between h and r genes you have to calculate recombination frequency

RF = Recombinants/Total offspring X 100

= 73+75/1846 X 100

= 8.01% approx 8cM distance between h and r gene

here h+ r and hr+ are parental type plaque

h+r+ and hr are recombinants

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