Question

Which environmental condition would NOT break hydrogen bonds in dsDNAs?

A) High salt concentration
B) High temperature
C) Solution with pH 2.3
D) Solution with pH 11.3
E) All above breaks hydrogen bonds

Answer 1

A) High salt concentration

B) High temperature

C) Solution with pH 2.3

D) Solution with pH 11.3

E) All above breaks hydrogen bonds.

Step-by-step explanation:

The correct answer is E) All above breaks hydrogen bonds. Hydrogen bonds are relatively weak interactions between the hydrogen atom of one molecule and an electronegative atom, usually oxygen or nitrogen, of another molecule. Breaking these hydrogen bonds is fundamental to processes involving DNA denaturation or unwinding.

A) **High salt concentration:** High salt concentrations can disrupt hydrogen bonds by shielding the charged phosphate groups in DNA. The ions in the salt solution compete with the hydrogen bonds, reducing their effectiveness.

B) **High temperature:** Increasing temperature imparts energy to the DNA molecules, facilitating the disruption of hydrogen bonds. This leads to the separation of the two DNA strands, a process known as denaturation.

C) **Solution with pH 2.3:** Low pH conditions, as in a solution with pH 2.3, indicate high acidity. Acidic conditions can protonate nitrogenous bases, disrupting hydrogen bonding between complementary bases and causing DNA denaturation.

D) **Solution with pH 11.3:** High pH conditions indicate alkalinity. Alkaline conditions can deprotonate the nitrogenous bases, also disrupting hydrogen bonds and promoting DNA denaturation.

Therefore, all the provided environmental conditions—high salt concentration, high temperature, acidic solution (pH 2.3), and alkaline solution (pH 11.3)—can break hydrogen bonds in dsDNA. Understanding these factors is crucial in molecular biology, genetics, and biotechnology, where manipulation of DNA structure is a common practice.

Answer 2

A) High salt concentration is the condition that would not break hydrogen bonds in dsDNA, as it can actually stabilize the double helix, contrary to high temperature, and extreme acidic or basic pH that can lead to DNA denaturation.

Step-by-step explanation:

The environmental condition that would not break hydrogen bonds in dsDNA among the options provided is high salt concentration (A).

High temperature (B) can denature DNA by disrupting hydrogen bonds, and extreme acidic (C, pH 2.3) and basic (D, pH 11.3) conditions can also lead to DNA denaturation.

However, high salt concentration generally has the effect of stabilizing the double helix by neutralizing the repulsion between the phosphate groups of the DNA, thus it is not associated with breaking hydrogen bonds.

While halophiles indeed prefer high salt conditions, this preference does not relate to DNA stability. Therefore, option E (All above breaks hydrogen bonds) is not correct.