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प्रश्न
What is the difference between a nucleoside and nucleotide?
उत्तर १
A nucleoside is formed by the attachment of purine or pyrimidine base to the 1-position of a pentose sugar.
On the other hand, a nucleotide is a unit formed by the attachment of nucleoside to phosphoric acid at the 5′-position of the sugar moiety.
उत्तर २
A nucleoside contains only two basic components of nucleic acids i.e., a pentose sugar and a nitrogenous base. It is formed when 1- position of pyrimidine (cytosine, thiamine or uracil) or 9-position of purine (guanine or adenine) base is attached to C -1 of sugar (ribose or deoxyribose) by a β-linkage. Nucleic acids are also called polynucleotides since the repeating structural unit of nucleic acids is a nucleotide.
A nucleotide contains all the three basic . components of nucleic acids, i.e., a phosphoric acid group, a pentose sugar and a nitrogenous base. These are obtained by esterification of C5, – OH group of the pentose sugar by phosphoric acid.
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संबंधित प्रश्न
The two strands in DNA are not identical but are complementary. Explain.
What is the difference between Nucleotide and Nucleoside?
The nucleic acid base having two possible binding sites is ____________.
Read the passage carefully and answer the questions that follow:
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Strengthening the Foundation: Chargaff Formulates His "Rules" Many people believe that James Watson and Francis Crick discovered DNA in the 1950s. In reality, this is not the case. Rather, DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher. Then, in the decades following Miescher's discovery, other scientists- notably, Phoebus Levene and Erwin Chargaff- carried out a series of research efforts that revealed additional details about the DNA molecule, including its primary chemical components and the ways in which they joined with one another. Without the scientific foundation provided by these pioneers, Watson and Crick may never have reached their groundbreaking conclusion of 1953: that the DNA molecule exists in the form of a three-dimensional double helix. |
Answer the following questions:
- A segment of DNA has 100 adenine and 150 cytosine bases. What is the total number of nucleotides present in this segment of DNA?
- A sample of hair and blood was found at two sites. Scientists claim that the samples belong to same species. How did the scientists arrive at this conclusion?
- The sample of a virus was tested and it was found to contain 20% adenine, 20% thymine, 20% guanine and the rest cytosine. Is the genetic material of this virus (a) DNA-double helix (b) DNA-single helix (c) RNA? What do you infer from this data?
OR
How can Chargaff’s rule be used to infer that the genetic material of an organism is double-helix or single-helix?
DNA fingerprinting is used to determine paternity of an individual. Which property of DNA helps in the procedure?
