D. UV light absorption of single-stranded DNA is lower than that of double-stran
ID: 189785 • Letter: D
Question
D. UV light absorption of single-stranded DNA is lower than that of double-stranded DNA.
E. Adding urea in the solution with DNA will increase Tm. Urea can disrupt non-covalent interactions
× y D Hw.pdf × Biology question lChegg.c × C Secure https://rid-72034087_1/courses/11369 11451 11506.201810/HW1.pdf HW1.pdf 3 14 figure. If the answer is F, please justify your aswer100 (15 pt) A. Increasing heat can denature DNA molecules. Low sal B. The higher the content of A:T base pairs, the 20 higher the melting temperature (Tm). High salt C) C. Increasing salt concentration of the solution make it difficult to denature the double-stranded DNA D. UV light absorption of single-stranded DNA is lower than that of double-stranded DNA. 12:47 PM 2/3/2018Explanation / Answer
D. FALSE. This can be explained by Hypochromic effect,i.e., the decreasing ability of a material to absorb light. The absorption decreases as DNA gets double stranded. The nucleic acids absorb in the UV region due to the conjugated double bond and ring systems of the constituent purines and pyrimidines. The hydrogen bonds between the paired bases in double stranded DNA limits the resonance of the aromatic ring of the base decreasing the UV absorption. As the single stranded DNA molecules have no complementary base pairing, they do not have the hydrogen bonds limiting their absorption and therefore absorbs more than double stranded DNA.
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