Hydrogen bonding between complementary

The two strands which make up DNA are held together by hydrogen bonds between complementary pairs of bases adenine paired with thymine and guanine paired with cytosine. The integrity of the genetic code (and of life as we know it) depends on error-free transmission of base-pairing information. 

The two strands of nucleotides in a DNA molecule are held together by hydrogen bonding between complementary nitrogenous bases adenine with thymine and guanine with cytosine. 

Ribosomal RNA (rRNA) is involved in the protein synthesis. It is found in the ribosomes which occur in the cytoplasm. Ribosomes contain about 35% protein and 65% rRNA. Experimental evidence suggests that rRNA molecules have structures that consist of a single strand of nucleotides whose sequence varies considerably from species to species. The strand is folded and twisted to form a series of single stranded loops separated by sections of double helix, which is believed to be formed by hydrogen bonding between complementary base pairs. The general pattern of loops and helixes is very similar between species even though the sequences of nucleotides are different. However, little is known about the three dimensional structures of rRNA molecules and their interactions with the proteins found in the ribosome. 

Hydrogen bonds are not just important for small molecules. Duplex strands of DNA and RNA are held together by hydrogen bonds between complementary purine and pyrimidine bases. Because each individual bond is weak it is possible to unzip these large molecules and use the primary sequence in transcription (for sequence copying) or translation (for protein synthesis) and zip up the hydrogen bonds after the information has been accessed by transcription and translation enzymes. Transfer of encoded information can therefore occur without destroying the sequences of the parent compound. 

Answer The double-helical structure is stabilized by hydrogen bonding between complementary bases on opposite strands and by base stacking between adjacent bases on the same strand. Base stacking in nucleic acids causes a decrease in the absorption of UV light (relative to the non-stacked structure). On denaturation of DNA, the base stacking is lost and UV absorption increases. 

Then we will turn our attention to blends of block copolymers where the self-assembly is dominated by multiple hydrogen bonding between complementary blocks of the two constituents. The self-assembly of some of these systems has features in common with that of star copolymers and allows one to study the consequences of this architecture for the structures formed [43-45]. 

FIGURE 9.22 The cloverleaf depiction of transfer RNA. Double-stranded regions (shown in red) are formed by folding the molecule and stabilized by hydrogen bonds between complementary base pairs. Peripheral loops are shown in yellow. There are three m or loops (numbered) and one minor loop of variable size (not numbered). 

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