Botany MCQs for NEET — Practice Questions with Answers

The purine and pyrimidine pairs of complementary strands of DNA are held together by hydrogen bonds (H-bonds). In DNA, adenine (a purine) pairs with thymine (a pyrimidine) with the help of 2 hydrogen bonds, and guanine (a purine) pairs with cytosine (a pyrimidine) with the help of 3 hydrogen bonds. This hydrogen bonding is crucial for the stability and specificity of the DNA double helix structure.

The two strands of the DNA duplex are antiparallel and complementary. 'Antiparallel' means that the two strands run in opposite directions, which is essential for the base pairs to align properly and form hydrogen bonds. 'Complementary' means that each base on one strand pairs with a specific base on the opposite strand (A with T, and G with C).

The code AUG is known as the start codon and it stands for the amino acid methionine. In the process of translation, AUG signals the start of protein synthesis and recruits the initiator tRNA carrying methionine to the ribosome.

An anticodon is a sequence of three bases in a tRNA molecule that is complementary to a codon sequence in mRNA. It allows the tRNA to bring the correct amino acid during protein synthesis by matching the codon on the mRNA sequence.

A codon is a sequence of three nucleotides on an mRNA molecule that specifies a particular amino acid or a stop signal during protein synthesis. This is known as the triplet code.

DNA replication requires both DNA polymerase and DNA ligase. DNA polymerase synthesizes the new DNA strand by adding nucleotides, while DNA ligase joins the Okazaki fragments on the lagging strand, sealing nicks in the sugar-phosphate backbone.

Okazaki fragments are short sequences of DNA nucleotides which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication. This occurs because DNA polymerase can only add nucleotides to the 3' end of a DNA strand, necessitating the synthesis of the lagging strand in short, separated segments.

DNA polymerase is the enzyme responsible for synthesizing new DNA strands by adding nucleotides to an existing chain during DNA replication. It plays a crucial role in the multiplication (replication) of DNA by ensuring the correct sequence of nucleotides is added to the growing DNA strand.

The amino acid attachment site on tRNA is located at the 3' end of the molecule. This is where the amino acid is covalently bonded to the tRNA during protein synthesis, allowing the tRNA to deliver the correct amino acid to the ribosome for incorporation into the growing polypeptide chain.

Replication is the process by which DNA makes a copy of itself during cell division. This is a crucial process to ensure that each new cell has the same genetic material as the parent cell.