The melting temperature (𝑡𝑚) of DNA is higher when the content of:
A. A:T base pairs is higher.
B. G:C base pairs is higher.
C. A:T base pairs is same as G:C base pairs.
D. G:C base pairs is lower

Title: Why G:C Base Pairs Increase the Melting Temperature of DNA

Slug: gc-base-pairs-dna-melting-temperature

Meta Description: Discover why DNA with higher G:C content has a greater melting temperature. Learn how base pair composition affects DNA stability and denaturation.

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Understanding DNA Melting Temperature (Tm)

The melting temperature (Tm) of DNA refers to the temperature at which 50% of the double-stranded DNA becomes single-stranded. This process is known as denaturation, and the Tm is influenced by several factors, most notably the base pair composition.

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Base Pair Basics: A:T vs G:C

DNA is composed of four nucleotide bases:

• Adenine (A) pairs with Thymine (T) via two hydrogen bonds
• Guanine (G) pairs with Cytosine (C) via three hydrogen bonds

Because G:C base pairs form more hydrogen bonds than A:T base pairs, they contribute more stability to the DNA helix.

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Why G:C Content Raises DNA Melting Temperature

The more G:C base pairs present in a DNA molecule:

• The stronger the hydrogen bonding network
• The higher the energy required to denature the DNA

Thus, DNA strands with higher G:C content will have a higher melting temperature (Tm).

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Correct Answer: B. G:C base pairs is higher

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Why Other Options Are Incorrect

• A. A:T base pairs is higher: Fewer hydrogen bonds → lower Tm
• C. A:T same as G:C: Moderate Tm, not the highest
• D. G:C base pairs is lower: Less stability → lower Tm

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Practical Applications

• PCR Optimization: Primers with higher G:C content require higher annealing temperatures
• DNA Hybridization: Stability of hybridized strands depends on base composition

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