DNA Structure and Analysis/DNA Replication and Recombination-Questions and Answers Graded A+

DNA Structure and Analysis/DNA Replication and Recombination-Questions and Answers Graded A+ A) How were scientists able to determine that DNA, and not some other molecule, serves as the genetic material in bacteria and bacteriophages? B) How do we know that DNA also serves as the genetic material in eukaryotes such as humans? C) How was it determined that the structure of DNA is a double helix with the two strands held together by hydrogen bonds formed between complementary nitrogenous bases? D)How do we know that G pairs with C and that A pairs with T as complementary base pairs are formed? - ANSWER-A) Transformation studies showed that DNA is the genetic material in bacteria. Differential labeling showed that DNA is the genetic material in some viruses. B) The action spectrum of UV light overlaps the absorption spectrum of DNA. Transgenic organisms can be generated with transferred DNA. DNA quantity in the nucleus varies with ploidy. DNA is abundant only in organelles that perform genetic functions. C/D) Determined by X-ray diffraction. The bases were stacked on top of each other like a chain. Chargaff found the four nitrogenous bases He also revealed that there equal proportions of purines (A+G) to pyrimidine (C+T). In addition, the base compositions were of equal proportion of A and T and of G and C. Most center around DNA and RNA and their role of serving as the genetic material. Write a short essay that contrasts these molecules, including a comparison of advantages conferred by their structure that each of them has over the other in serving in this role. (DNA vs RNA) - ANSWER- Discuss the reasons proteins were generally favored over DNA as the genetic material before 1940. What was the role of the tetranucleotide hypothesis in this controversy? - ANSWER-There was more research done on proteins than DNA. They were abundant, diverse molecules and DNA was considered to be not diverse enough to carry the genetic code. The hypothesis thought that DNA was exactly 25% A, G, T, and C. Contrast the contributions made to an understanding of transformation by Griffith and by Avery and his colleagues. - ANSWER-Griffith was the first to observe (and name) the phenomenon of transformation, using an in vivo system (laboratory mice). He observed that a bacterial mixture containing heat-killed cells of a virulent strain of Diplococcus pneumoniae and live cells of an avirulent strain killed the injected mice and led to recovery of live cells of the virulent strain. He concluded that the heat-killed virulent bacteria transformed the avirulent strain into a virulent strain. He did not identify the "transforming principle." By contrast, Avery and coworkers, using in vitro techniques,