4. What components of the nucleotide monomers make the backbone of polynucleotid

Question

4. What components of the nucleotide monomers make the backbone of polynucleotides, and what component determines the different DNA sequences? What bonds help DNA double-helix form stable structure?

5. What are the four bases found in DNA molecules? How base pairs are formed between these bases, and the hydrogen bond numbers between different base pairs?

6. How do RNA polynucleotides differ from DNA polynucleotides? Which base is changed to Uracil in RNA when they are transcribed from DNA? Do RNA molecules usually form double helix?

7. Who proposed the DNA tertiary structure as double helix? What parts of DNA molecules are located outside, and what parts are located inside of double helix?

Explanation / Answer

Answer 4:
The monomeric units of nucleic acids are called as nucleotides.
Nucleotides are phosphate esters of nucleosides and made up of three components:
1. A base that has a nitrogen atom
2. A five-carbon sugar
3. An ion of the phosphoric acid
The four components thymine, adenine, cytosine and guanine determines the physical order of the DNA molecule.
The helical structure of dsDNA is stabilized by non-covalent interaction. These interaction includes stacking interaction between adjacent bases and the hydrogen bond between complementary strands.
Answer 5: the four bases of DNA molecule is thymine, adenine, cytosine and guanine.
Thymine base pair with adenine via the double bond.
Cytosine base pair with guanine via the triple bond.
Answer 6: DNA contains thymine, adenine, cytosine and guanine but in RNA in place of thymine, uracil is present. RNA has a ribose sugar instead of a deoxyribose sugar like DNA. Deoxyribose is the same as ribose, except that it consists of one more OH.
RNA forms double helix through intrastrand complementary base pairing as in tRNA.
Answer 7: Watson and Crick proposed the DNA tertiary structure as the double helix.
Nitrogenous bases are located inside while sugar-phosphate backbone is located outside.

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