Q.48 The amount of agarose required to prepare 250 𝑚𝐿 of 0.8% agarose gel
is __________ 𝑔𝑟𝑎𝑚𝑠 (rounded off to the nearest integer).

2 grams of agarose are required to prepare 250 mL of 0.8% agarose gel. This calculation uses the standard weight/volume (w/v) formula for gel concentration, rounded to the nearest integer.​

Calculation Method

Agarose gel percentage is defined as grams of agarose per 100 mL of buffer (w/v). For 0.8%, dissolve 0.8 g agarose in 100 mL buffer.​
Scale proportionally: Mass (g) = (0.8 / 100) × 250 mL = 2.0 g.​
Round 2.0 to the nearest integer: 2 g.

Step-by-Step Preparation

• Weigh 2 g agarose powder.​

• Add to ~200 mL electrophoresis buffer (TAE or TBE) in a flask.​

• Microwave to dissolve (swirl to avoid boiling), cool to ~60°C, add dye if needed, pour into gel tray.​
  A 0.8% gel suits DNA fragments of 1–10 kb.​

Agarose Gel Concentrations

CSIR NET Exam Context

This fill-in-the-blank question tests precise calculation skills for molecular biology techniques. No options provided; direct computation yields 2 g. Verify units (mL, %, g) to avoid errors like confusing v/w.​

Agarose gel electrophoresis remains essential in molecular biology for DNA separation, and agarose gel calculation for precise concentrations like 0.8% agarose gel is a core skill for CSIR NET aspirants. This guide solves “amount of agarose required to prepare 250 mL of 0.8% agarose gel” with detailed math, protocol, and exam tips.​

Agarose Percentage Explained

Agarose gel concentration uses w/v: 0.8% = 0.8 g per 100 mL buffer. Higher % creates smaller pores for better small-fragment resolution; 0.8% excels for 1–10 kb DNA. Common range: 0.5–2%.​

Exact Calculation for 250 mL 0.8% Gel

Formula: Mass (g) = (% / 100) × Volume (mL)
= (0.8 / 100) × 250 = 2.0 g (rounds to 2 grams).​
Pro Tip: Use analytical balance; errors in scaling lead to poor resolution.​

Full Preparation Protocol

1. Weigh 2 g agarose.​

2. Add to 250 mL 1× TAE/TBE in 500 mL flask.​

3. Microwave (1–2 min, swirl every 30 s).​

4. Cool to 60°C, add EtBr (0.5 μg/mL), pour into tray with comb.​

5. Solidify 20–30 min; run at 5–10 V/cm.​

CSIR NET Tips for Agarose Questions

• Recognize w/v units; avoid v/w mix-ups.​

• 0.8% suits plasmids/PCR; memorize ranges.​

• Practice: For 50 mL 1%, use 0.5 g.​
  Master this for Unit 2 (Techniques) scoring.​