GC content and DNA melting temperature
Why does the GC content of a particular DNA molecule affect the melting of the two strands?
a. The G and C bond only requires two hydrogen bonds, thus requiring a lower temperature to “melt” the DNA.
b. Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
c. The percentage of As and Ts in the molecule is more important to melting temperature than the percentage of Gs and Cs.
d. The nucleotide content of a DNA molecule is not important to know for biotechnology and molecular biology research.
Correct Answer: ✅ (b) Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Explanation
The melting temperature (Tm) of a DNA molecule refers to the temperature at which 50% of the DNA strands separate (denature) into single strands. The GC content of a DNA molecule plays a critical role in determining its melting temperature because of the number and strength of hydrogen bonds between the base pairs:
🧬 1. Hydrogen Bonding in Base Pairs
- Guanine (G) and Cytosine (C) base pairs are held together by three hydrogen bonds.
- Adenine (A) and Thymine (T) base pairs are held together by two hydrogen bonds.
✅ Higher GC Content → Higher Melting Temperature
- More hydrogen bonds = Greater thermal stability
- DNA molecules with a higher GC content require more heat to break the hydrogen bonds and separate the strands.
- Therefore, DNA with a high GC content has a higher melting temperature (Tm) than DNA with a high AT content.
✅ 2. Why the Other Options Are Incorrect
| Option | Explanation | True/False |
|---|---|---|
| (a) The G and C bond only requires two hydrogen bonds, thus requiring a lower temperature to “melt” the DNA. | G-C pairs require three hydrogen bonds, not two, so this is incorrect. | ❌ False |
| (b) Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA. | Correct – More hydrogen bonds = Higher melting temperature. | ✅ True |
| (c) The percentage of As and Ts in the molecule is more important to melting temperature than the percentage of Gs and Cs. | GC content has a greater influence on melting temperature than AT content. | ❌ False |
| (d) The nucleotide content of a DNA molecule is not important to know for biotechnology and molecular biology research. | Nucleotide content is critical in genetic research and biotechnology. | ❌ False |
🔬 3. Factors Affecting DNA Melting Temperature
✅ 1. GC Content:
- Higher GC content = Higher Tm due to more hydrogen bonds.
✅ 2. DNA Length:
- Longer DNA molecules have more hydrogen bonds → Higher Tm.
✅ 3. Salt Concentration:
- Higher salt concentration stabilizes the DNA double helix → Higher Tm.
✅ 4. pH:
- Extreme pH values can destabilize hydrogen bonds → Lower Tm.
✅ 5. Presence of Mismatched Base Pairs:
- Mismatches weaken the DNA helix → Lower Tm.
🧪 4. How to Calculate Melting Temperature (Tm)
A common formula to estimate Tm for short DNA sequences:
Tm=4(G+C)+2(A+T)T_m = 4(G + C) + 2(A + T)
Where:
- G = Number of guanine bases
- C = Number of cytosine bases
- A = Number of adenine bases
- T = Number of thymine bases
For longer sequences, the more accurate calculation based on the nearest-neighbor thermodynamic model is used.
🌡️ 5. Importance of GC Content in Molecular Biology
✅ 1. PCR Optimization:
- Primers with high GC content require higher annealing temperatures.
✅ 2. DNA Sequencing:
- High GC regions are harder to sequence due to stronger binding.
✅ 3. Gene Cloning:
- High GC content can affect cloning efficiency and success.
✅ 4. Evolutionary Biology:
- GC content varies between species → Used in evolutionary studies.
🚀 6. Applications of GC Content Analysis
✅ 1. PCR Primer Design:
- High GC primers require higher annealing temperatures.
✅ 2. Genome Stability:
- High GC content = Greater thermal stability.
✅ 3. Species Identification:
- GC content is species-specific and used for taxonomic classification.
Summary
- GC base pairs have three hydrogen bonds → Higher thermal stability.
- High GC content = Higher melting temperature (Tm).
- GC content influences PCR efficiency, DNA sequencing, and gene expression.
- ✅ Correct Answer: (b) Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
72 Comments
Nisha
March 17, 2025Done
Akshay mahawar
March 17, 2025Done
Arushi
March 17, 2025👍
Suman bhakar
March 20, 2025Done
Parul
March 23, 2025Done easily.
Roopal Sharma
August 24, 2025G-C content is crucial for melting temperature and G-C has threee hydrogen bond in them .
Mohd juber Ali
August 24, 2025Option b is right bcz 3 hydrogen bond krne k liye jyada temperature need hogi for melting
Khushi Pareek
August 24, 20253 hydrogen bonds
Sakshi yadav
August 24, 2025For 3 H- bond more temp.required to break the bonds
Avni
August 24, 2025G and C base-pairing requires three hydrogen bonds and a higher temperature is required to denature the DNA.
Arushi Saini
August 24, 20253 h bonds are present between G and C hence high temperature is required to melt the DNA
Mansukh Kapoor
August 24, 2025The correct answer is option 2nd
G and C base-pairing requires 3 hydrogen bonds and a higher temperature is required to melt the DNA
Neha Yadav
August 24, 2025GC content affect the melting point of DNA mol is due to the G and C base pairing required 3 hydrogen bonding and high temp is required to melt the DNA
Khushi Agarwal
August 24, 2025Correct Answer: ✅ (b) Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
karishma don
August 24, 2025due to 3 hydrogen bond between G and C it requires high temp to melt it
Anurag Giri
August 24, 2025Correct answer is 2nd
Bcoz Guanine (G) and Cytosine (C) base pairs are held together by three hydrogen bonds
Mahima Sharma
August 24, 2025G and C base-pairing requires 3 hB and a higher temperature is required to melt the DNA.
Reply
Aafreen Khan
August 24, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA
Dharmpal Swami
August 24, 2025G and C based pairing required 3 H boding
For melting these H bonding required high temperature
Aakanksha Sharma
August 24, 2025Bcz high temperature is require to melt the 3 hydrogen bond present between G and C
Priyanka Choudhary
August 24, 2025The right answer is option b,Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Karishma
August 24, 2025GC contant high so tem high..
HIMANI FAUJDAR
August 24, 2025Ans Correct answer is G and C required 3 hydrogen bonds for base pairing so the high temperature is also required for the melting of these H – bonds.
Dipti Sharma
August 24, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Priya dhakad
August 24, 2025G and C required 3 H- bonds for base pairing so the high temperature is also required for the melting .
AKANKSHA RAJPUT
August 24, 2025Correct answer is 2nd
Sneha Kumawat
August 24, 2025Gc pairing required 3 hydrogen bonding
So high temp is also required for melting
Santosh Saini
August 24, 2025B statement is correct bcz G and C base pairing requires 3 hydrogen bonds, so High temperature is required for melting of DNA
anjani sharma
August 24, 2025For melting of 3 bonds in GC ,high temperature is required
Heena Mahlawat
August 24, 2025G and C form 3 hydrogen bonds , so higher temperature is needed to melt as compared to AT pairing
Tanvi Panwar
August 24, 2025G and C NTS have 3 hydrogen bonds that requires high temperature for melting.
Nilofar Khan
August 28, 2025Correct answer is b.
G and C have 3 hydrogen bond. So required high temp for melting.
MOHIT AKHAND
August 24, 2025Done sir ✅
Ayush Dubey
August 24, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA
Surbhi Rajawat
August 24, 2025GC base pairing requires 3 hydrogen bond, therefore it is hard to melt
Neelam Sharma
August 24, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Aman Choudhary
August 24, 2025G and C base pairing require three hydrogen bond and a high temperature is required for melt the DNA
Samiksha bajiya
August 24, 2025Because G and C base pairing required three hydrogen bonding and a high temperature is required for melt the DNA
Bhawna Choudhary
August 24, 2025Correct answer is B
Bharti Yadav
August 24, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Priyanka Verma
August 24, 2025Option B is correct – G and C base pairing has 3 H-bonds, so it requires high melting point.
Monika jangid
August 24, 2025Option b is correct bcoz 3 bonds r present between g and c so for melting requirement of higher temp
Varsha Tatla
August 25, 2025Done
Divya rani
August 25, 2025Gc pair affects the melting because for GC pairing we require three hydrogen bonds and for breaking these bonds very high temperature is needed.
shruti sharma
August 25, 2025Becoz G and C base pair required three hydrogen bonding and high temp.dna melt
Payal Gaur
August 25, 2025G and C require high tempr to break the hydrogen bond (three hydrogen bond form between GC)
Minal Sethi
August 25, 2025G-C have 3 hydrogen bonds so higher GC content requires more temperature to break down the H-bonding
Bhavana kankhedia
August 26, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Surendra Doodi
August 26, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA. Best Institute for CSIR NET Life Science Coaching – Let’s Talk Academy”
Vanshika Sharma
August 26, 2025G C req high temp bcz it has three H bonds
Devika
August 26, 2025G and C have three hydrogen bonds so they require higher temperature to melt
Shivani
August 26, 2025G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Rishita
August 26, 2025Opt.b
Simran Saini
August 26, 2025Because G and C base pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Sakshi Kanwar
August 27, 2025G and C binds with each other with 3 hydrogen bond which require high temperature to melt the DNA
Muskan singodiya
August 28, 2025Option b
Kanica Sunwalka
August 28, 2025G-C have 3 hydrogen bond = require more temp for brk down
Deepika Sheoran
August 28, 2025Option B is correct .
3 Hydrogen bond from between GC.
G & C require high temperature to break the hydrogen bond..
Kajal
August 28, 2025Gc pair affect the melting of dna gc have 3hydrogen bonds so need more energy to break option b is correct
Neeraj Sharma
August 28, 2025GC needs more temp or energy in order to break the three hydrogen bonds
Anisha Beniwal
August 28, 2025Option B -GC have 3 HB
Mitali saini
August 29, 2025Correct Answer: ✅ (b) Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Asha Gurzzar
August 30, 2025B is correct beacuse three hydrogen bonds to be breaked to break G and c hence it lead to the melting of the dna strands
Khushi Singh
August 30, 2025GC need 3 hydrogen bond for pairing which means high temperature for melting so affects melting point
Sonam Saini
August 30, 2025G o C ki spelling ke liye teen hydrogen ki avashyakta hoti hai lekin DNA ko pighlaane ke liye kuchh tapman ki avashyakta hoti hai
Kirti Agarwal
August 31, 2025Opt b
Kajal
August 31, 2025Correct Answer is (b) Because G and C base pairing requires three hydrogen bonds and a higher temperature is required to melt the DNA
Aartii sharma
August 31, 2025(b) G and C base pairing requirs threehydrogen bonds and a higher temperature is required to melt the DNA
Konika Naval
August 31, 2025G and C base-pairing requires three hydrogen bonds and a higher temperature is required to “melt” the DNA.
Konika Naval
August 31, 2025G and C base-pairing requires three hydrogen bonds and a higher temperature is required to melt the dna
Konika Naval
August 31, 2025G and C base-pairing requires three hydrogen bonds and higher temp
Muskan Yadav
September 8, 2025Because G and C base-pairing requires three hydrogen bonds and a higher temperature is required to melt the DNA.