1. What is GC Content?

GC content refers to the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). It's an important characteristic of genomes and genes that can affect their stability and function.

2. How Does the Calculator Work?

The calculator uses the GC content formula:

Where:

• \( G \) — Count of guanine bases
• \( C \) — Count of cytosine bases
• \( L \) — Total length of the sequence

Explanation: The calculator counts all G and C bases in the input sequence, divides by the total sequence length, and multiplies by 100 to get a percentage.

3. Importance of GC Content

Details: GC content is important in PCR primer design, genome studies, and understanding DNA stability (GC pairs form three hydrogen bonds versus AT pairs which form two). It can also influence gene expression and is used in taxonomy studies.

4. Using the Calculator

Tips: Paste your DNA sequence in FASTA format (with or without header). The calculator will automatically:

• Remove any FASTA header lines
• Convert to uppercase
• Remove non-DNA characters
• Calculate GC content

5. Frequently Asked Questions (FAQ)

Q1: What's a typical GC content range?
A: In humans, average GC content is about 41%. Bacteria range from 25-75%. Extremophiles often have very high GC content.

Q2: Why does GC content matter in PCR?
A: GC-rich sequences require higher melting temperatures. Knowing GC content helps set proper PCR conditions.

Q3: How does GC content affect DNA stability?
A: GC pairs form three hydrogen bonds (vs two in AT pairs), making GC-rich DNA more thermally stable.

Q4: Should I include the FASTA header?
A: The calculator works with or without the header. It will automatically remove any lines starting with ">".

Q5: What about RNA sequences?
A: The calculator works for RNA too - just remember it will convert all U's to T's (as it treats input as DNA).