In the The Meselson-Stahl experiment, Escherichia coli, grown for a period of time in 15N, was transferred to 14N for one generation of DNA replication, the resulting DNA should have 14N added to all "new" DNA. When DNA was extracted from cells one generation after transfer to light medium and analyzed by analytical ultracntrifugation, this DNA was found:

a. in one band/position in the ultracentrifuge tube, consistent either with semiconservative or dispersive models for replication.
b. in two bands/positions in the ultracentrifuge tube, consistent with conservative replication..
c. in one band/position in the ultracentrifuge tube, consistent only with semiconservative replication.
d. in one band/position in the ultracentrifuge tube, consistent only with dispersive replication.
e. in two bands/positions in the ultracentrifuge tube, consistent either with semiconservative or dispersive models for replication..

Aperson with age is more likely to catch diseases that healthy people usually don’t catch.what are these infections called?

The human genome project is devoted to mapping the general dna sequence of our species. this could lead to the development of new medicines, as well as the possibility of using gene therapy to treat certain diseases. however, there are some ethical issues surrounding the mapping of individual genomes. one concern is a) that your genes may change over time, making the project useless. b) that insurance companies could discriminate based on genetic make-up. c) that since this has never been done before, we should probably not do it now. d) that sequencing our individual genomes is so expensive, it is a counter-productive strategy.

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.