Molecular Basis of Inheritance
Read the following passage carefully and answer the questions given below:
In the process of translation, genetic information is translated from the language of nucleic acid polymers to the language of amino acid polymers. There is no complementarity between amino acids and nucleotides, nor can this be thought of chemically. This led to the proposal of a genetic code that would direct the sequence of amino acids during protein synthesis. In eukaryotes, monocistronic structural genes are found, in which interrupted coding sequences are present. Coding sequences, or expressed sequences, are called exons. Exons are interrupted by unexpressed sequences called introns.
The length of DNA usually depends on the number of nucleotides present in it. It is a characteristic feature of an organism. For example, a bacteriophage called φ × 174 has 5386 nucleotides, bacteriophage lambda has 48502 base pairs (bp), and Escherichia coli has 4.6 × 106 base pairs (bp). There are three major types of RNA: mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA). In eukaryotes, RNA is needed for the synthesis of proteins in ribosomes. DNA obtained from sources such as blood, blood spots, hair, skin, bone, semen, etc. has one or more polymorphisms, which are very useful in forensic applications.
The haploid DNA in humans has:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 3.3 × 109 base pairs
The length of DNA is given as the number of base pairs (bp) it has. The number is a feature of each organism. The haploid content of human DNA, that is the DNA in one set of 23 chromosomes, is 3.3 × 109 bp. A diploid human cell has twice this amount.
(1) 6.6 × 109 base pairs — Incorrect. This is about the DNA of a diploid human cell, double the haploid amount.
(2) 4.6 × 106 base pairs — Incorrect. This is the DNA of the bacterium Escherichia coli, given in the passage.
(3) 3.3 × 109 base pairs — Correct. This is the haploid human DNA content.
(4) 3.3 × 106 base pairs — Incorrect. The number is right but the power of ten is wrong. It is a thousand times too small.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
The DNA –
