9. What are Chargaffs rules and explain what evidence it provides for the struct
ID: 206430 • 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 = 3396, T= 18%. Cs24%. 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 binds to T and G binds to C. It is called as Chargaff's rule.
A==T, G==C.
A+T+G+C = 100%; A+G = T+C
A) The G+C = 60%. As A+T+G+C = 100%, A+T = 100 -60 = 40.
So, the proportion of each nucleotides in percentages =
G+C = 60%, so % of G = 60/2 = 30%; % of C = 60/2 = 30%.
A+T = 40%, so % of A = 40/2 = 20%; % of T = 40/2 = 20%.
B) According to Chargaff's rule, A==T, G==C.
As the %A not equals to %T and %G not equals to %C, the DNA is single stadarad DNA.
10. The place where DNA replication starts is called as Ori region(Prokarytic) or ARS regions (Eukaryotic).
B) In prokaryotes only one ori or replication start sequences are present.
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