NEET Practice Questions (MCQs) with Answers & Solutions

Gene pool is the total gene present in a population. Genome is the total genetic constitution of an organism. Codon is the basic unit of genetic code, a sequence of three adjacent nucleotide in DNA or mRNA that code for an amino acid. Gene is the basic unit of heredity; a sequence of DNA nucleotide that encodes a protein.

Cistron is a segment of DNA nucleotides that codes for a polypeptide chain. Triplet is a three nucleotides sequence coding for an amino acid.

Therefore,

codon  $\approx$ triplet

cistron $\approx$ gene

DNA fingerprinting is technically called DNA profiling or DNA typing.

tRNA has four recognition sites among these one is the amino acid attachment site. It has the amino acid attachment site with the 3’ terminal – CCA sequence.

The two DNA strands are held together by weak (hydrogen) bonds between the bases on each strand, forming base pairs. Genome size is usually stated as the total number of base pairs; the human genome contains roughly 3 billion base pairs.

Southern blotting was named after Edward M. Southern who developed this procedure in Edinburgh University in the 1970’s. Southern blotting is designed to locate a particular sequence of DAN within a complex mixture. The amount of DNA needed for this technique is dependent on the size and specific activity of the probe. Before, starting the procedure, the desired DNA should be isolated from a specific nucleated cell.

Lysine is encoded by the codons AAA and AAG.

Non sense codon or terminator codon are the codons that do not code for any amino acid. It is a set of three nucleotides for which there is no corresponding tRNA molecule to insert an amino acid into the polypeptide chain. Protein synthesis is hence terminated and the completed polypeptide released from the ribosome. Three stop codons are UAA (ochre), UAG (amber) and UGA (opal).

Mutations which generate any of these three codons in a position which normally contains a codons in a position which normally contains a codon specifying an amino acid are known as nonsense mutations.

The anticodon loop of tRNA binds to the codon on mRNA during translation. The CCA end of tRNA binds to the amino acid, which is then added to the growing polypeptide chain. This is the correct binding pattern of tRNA with mRNA and amino acids during protein synthesis.

Extragenic or intergenic suppression reveals the effect of a mutation in a gene at a different place within the genome.

It can be explained as a mutation disrupting the complementary interaction between protein molecules which can be compensated by a second mutation occuring at some place in the genome restoring or providing a suitable alternative interaction between those molecules.

If one base is coding one amino acid then (12)¹ = 12, but we have 96 amino acids. Suppose two bases form one codon, then (12)² = 144. It is sufficient to code 96 or 20 amino acids and hence two, bases form one codon.