question 1 , after one round of replication in heavy medium, meselson and Stahl

Question

question 1 , after one round of replication in heavy medium, meselson and Stahl observed a single band in their density gradient centrifugation experiment density. which model for DNA replication did this support?

question 2,

can you please explain the answers

c, Widespread reductions in gene expression. fd A and B e. B and C 721. You are attempting to clone a gene into a bacterial vector containing both a gene encoding resistance to the antibiotic kanamycin, and a lacz marker containing the vector's multiple cloning site. You plate your transformed cells onto media containing and What colonies are you going to chose to ensure you have successfully cloned your gene? a, Colonies that grow on kanamycin and are blue. b Colonies that grow on kanamycin and are white C. Colonies that do not grow on kanamycin and are blue. d Colonies that do not grow on kanamycin and are white.

Explanation / Answer

(1) In the first round of the Meselson and Stahl experiment, an intermediate band is obtained with a hybrid of light and heavy DNA. This result supports the dispersive and semi-conservative models.

(2) b. The colonies that grow on kanamycin and are white. The recombinants containing the gene of interest would naturally carry the kanamycin resistance gene and X-gal. When the cells are transformed onto a media containing both Kanamycin and X-gal, the bacterial colonies would have taken up the resistance gene and so they could grow on the medium containing the antibiotic. The cells transformed with the vector containing the recombinant DNA will produce white colonies.

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