9. What are Chargaffs rules and explain what evidence it provides for the struct
ID: 206407 • Letter: 9
Question
9. What are Chargaffs rules and explain what evidence it provides for the structure of DNA A) In a particular organism, 60% of the bases in its DNA are G or c. what are the individual percentages of A, T, G, and C in the DNA? B) A DNA sample has a base composition of: A = 25%, G = 33%. T=18%, C= 24%. Is this DNA single- or double-stranded? Explain your reasoning. 10. A) In a DNA molecule, name the sequence where replication starts. B) How many of these "replication start sequences" are found in a typical prokaryotic genome?Explanation / Answer
9. In DS DNA, A bind to T with three hydrogen bonds and G binds to C with three hydrogen bonds. It is reffered as Chargaff's rule. (A==T, G==C)
A+T+G+C = 100%. or A+G = T+C.
A. As A+T+G+C = 100%, GC = 60%. So, AT = 100- 60 = 40%.
As the A bind to T and G binds to C in equal proportions, the % of each nucleotide is
GC = 60%, So, G = 60/2 = 30% and C = 60/2 = 30%
AT = 40%, So, A = 40/2 = 20% and T = 40/2 = 20%.
B. Accroding to Chargaff's rule A==T and G==C, so, the observed data is not matches with chargaff's rule, which indicates that the DNA is single standard.
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