NEET Practice Questions (MCQs) with Answers & Solutions

Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA. It is a derivative of purine, a double-ringed molecule containing carbon and nitrogen atoms. Specifically, guanine pairs with cytosine in DNA through three hydrogen bonds, contributing to the stability of the DNA double helix.

Ribonucleosides are formed from ribonucleotides by the removal of the phosphate group. A ribonucleotide consists of a ribose sugar, a nitrogenous base, and a phosphate group. When the phosphate group is removed, the remaining part is called a ribonucleoside, which consists of the ribose sugar and the nitrogenous base.

DNA is primarily localized in the nucleus of eukaryotic cells. However, it is also found in mitochondria and chloroplasts. These organelles contain their own DNA, which is inherited maternally (in the case of mitochondria) and is crucial for the organelles' functions. Therefore, the correct answer is that DNA is localized in the nucleus, mitochondria, and chloroplasts.

A DNA strand is directly involved in the synthesis of another DNA strand through the process of replication, t-RNA through transcription, and m-RNA also through transcription. However, proteins are synthesized through translation, which involves m-RNA, t-RNA, and ribosomes, not directly by the DNA strand.

Nucleic acids were first discovered by Friedrich Miescher in 1869. He isolated a new substance from the nuclei of white blood cells, which he called 'nuclein,' later known as nucleic acids.

Nucleic acids, such as DNA and RNA, are involved in heredity. They carry genetic information that is passed from one generation to the next and are responsible for the storage, replication, and expression of genetic information.

Chemically, DNA and RNA differ primarily in their sugar and nitrogenous bases. DNA contains the sugar deoxyribose and the nitrogenous base thymine, while RNA contains the sugar ribose and the nitrogenous base uracil. This makes option o1 correct.

Nucleic acids are polymers made up of nucleotide monomers. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. Therefore, option o2 is correct.

A molecule of ATP (adenosine triphosphate) is structurally similar to a molecule of RNA because both contain the sugar ribose and the nitrogenous base adenine. ATP has three phosphate groups, whereas RNA nucleotides have one. Therefore, option o1 is correct.

Polysomes, or polyribosomes, are clusters of ribosomes bound to a single mRNA molecule. They are the site of protein synthesis in the cell, where translation of mRNA into a polypeptide chain occurs.