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668 questions in this collection · Page 14 of 67
Question 131 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
Which scientist is credited with the term "Nuclein" after isolating it from pus cells?
Friedrich Miescher identified a substance inside the nucleus of pus cells from surgical bandages and named it Nuclein. This was the first isolation of what we now know as genetic material.
Question 132 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
Who renamed "Nuclein" to "Nucleic Acid" due to its acidic nature?
While Friedrich Miescher discovered Nuclein, it was Altmann who later observed its acidic properties (due to phosphoric acid) and renamed it Nucleic Acid.
Question 133 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
In a DNA double helix, the two strands are coiled in which direction?
The standard B-form of DNA described by Watson and Crick is a right-handed helix, meaning it turns clockwise as it moves forward.
Question 134 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
Which form of DNA is considered the most common and dominant form in living organisms?
B-DNA is the most common form of DNA found in nature and is the structure described by the Watson and Crick double helix model.
Question 135 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
The distance between two adjacent base pairs in a B-DNA helix is approximately?
In B-DNA, the rise per base pair is 0.34 nanometers (or 3.4 Angstroms). Since there are 10 base pairs per turn, the total pitch is 3.4 nm.
Question 136 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
How many base pairs are present in one complete turn (pitch) of the B-DNA helix?
One complete 360-degree turn of the B-DNA helix contains 10 base pairs. This results in a pitch length of 34 Angstroms or 3.4 nm.
Question 137 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
The constant distance (diameter) between the two strands of the DNA double helix is?
The diameter of the DNA double helix is approximately 20 Angstroms (2 nm). This uniform width is maintained because a purine (double ring) always pairs with a pyrimidine (single ring).
Question 138 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
What ensures the uniform diameter of the DNA double helix?
The pairing of a double-ring purine with a single-ring pyrimidine ensures that the distance between the two strands remains constant at approximately 20 Angstroms throughout the helix.
Question 139 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
Which bond provides additional stability to the DNA double helix by interactions between stacked base pairs?
Besides hydrogen bonds between opposite bases, the plane of one base pair stacks over the other, creating stacking interactions (hydrophobic interactions) that confer additional stability to the helical structure.
Question 140 of 668
📘 CLASS XII
Molecular Basis Of Inheritance
Which bacteriophage has single-stranded DNA?
Bacteriophage Phi X 174 is unique because it contains single-stranded DNA comprising 5386 nucleotides, unlike most other organisms which have double-stranded DNA.