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Short, practical explainers on sequencing concepts — each paired with a calculator you can try straight away.

• How much sequencing coverage do I need? What coverage (read depth) means, typical targets for WGS, WES and RNA-seq, and how to plan reads for a run.
• What is Q30? Phred quality scores explained How the Phred scale turns base-call error probability into a Q score, what Q20/Q30/Q40 mean, and why %≥Q30 matters.
• Nearest-neighbor Tm vs the Wallace rule Two common ways to estimate primer melting temperature — the quick Wallace rule and the more accurate nearest-neighbor model — and when to reach for each.
• How much depth do you need to call a variant? Why the sequencing depth you need depends on a variant’s allele frequency, not just on sequencing more — and how rare variants raise the bar.
• Restriction enzymes and cut sites, explained What restriction enzymes recognise and cut, the difference between sticky and blunt ends, and why cut sites matter when planning a cloning strategy.
• How GC content affects PCR and sequencing Why GC-rich and AT-rich DNA cause real problems — secondary structure, weak priming and uneven coverage — even when the input amount is the same.
• Why ng/µL and nM aren’t the same thing A DNA concentration in mass per volume only becomes a molecule count once you know the fragment length — which is why molarity, not mass, drives loading.
• Why average coverage doesn’t tell the whole story A genome can have a healthy average depth and still contain unsequenced gaps, because reads land at random and coverage is a distribution, not a guarantee.
• Primer design basics: avoiding dimers and getting the clamp right What primer-dimers are, why the 3′ end of a primer matters more than people expect, and how a GC clamp helps — up to a point.
• Open reading frames and why the frame matters A DNA sequence can be read six different ways, and only some make biological sense — what reading frames and ORFs are, and why you check all six.