In your laboratory, you have an F− strain of E. coli that is resistantto streptomycin and is unable to metabolize lactose, but it can metabolizeglucose. Therefore, this strain can grow on a medium thatcontains glucose and streptomycin, but it cannot grow on a mediumcontaining lactose. A researcher has sent you two E. colistrains in two separate tubes. One strain, let’s call it strain A, hasan F′ factor (an F prime factor) that carries the genes that are requiredfor lactose metabolism. On its chromosome, it also has thegenes that are required for glucose metabolism. However, it is sensitiveto streptomycin. This strain can grow on a medium containinglactose or glucose, but it cannot grow if streptomycin is addedto the medium. The second strain, let’s call it strain B, is an F−strain. On its chromosome, it has the genes that are required forlactose and glucose metabolism. Strain B is also sensitive to streptomycin.Unfortunately, when strains A and B were sent to you, thelabels had fallen off the tubes. Describe how you could determine which tubes contain strain A and strain B.
Genetic Recombination
Recombination is crucial to this process because it allows genes to be reassorted into diverse combinations. Genetic recombination is the process of combining genetic components from two different origins into a single unit. In prokaryotes, genetic recombination takes place by the unilateral transfer of deoxyribonucleic acid. It includes transduction, transformation, and conjugation. The genetic exchange occurring between homologous deoxyribonucleic acid sequences (DNA) from two different sources is termed general recombination. For this to happen, an identical sequence of the two recombining molecules is required. The process of genetic exchange which occurs in eukaryotes during sexual reproduction such as meiosis is an example of this type of genetic recombination.
Microbial Genetics
Genes are the functional units of heredity. They transfer characteristic information from parents to the offspring.
In your laboratory, you have an F− strain of E. coli that is resistant
to streptomycin and is unable to metabolize lactose, but it can metabolize
glucose. Therefore, this strain can grow on a medium that
contains glucose and streptomycin, but it cannot grow on a medium
containing lactose. A researcher has sent you two E. coli
strains in two separate tubes. One strain, let’s call it strain A, has
an F′ factor (an F prime factor) that carries the genes that are required
for lactose
genes that are required for glucose metabolism. However, it is sensitive
to streptomycin. This strain can grow on a medium containing
lactose or glucose, but it cannot grow if streptomycin is added
to the medium. The second strain, let’s call it strain B, is an F−
strain. On its chromosome, it has the genes that are required for
lactose and glucose metabolism. Strain B is also sensitive to streptomycin.
Unfortunately, when strains A and B were sent to you, the
labels had fallen off the tubes.
Describe how you could determine which tubes contain strain A and strain B.
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