Most dna tests need between a few nanograms and a few micrograms of extracted dna, depending on the method and the question you want to answer.

Second cousins usually share about 3 percent of dna, though real test results can run a bit lower or higher.

One human cell holds about 6 billion DNA base pairs, and all your cells together pack an astonishing length of DNA.

Most human cells hold about 6 picograms of dna, roughly 6 billion base pairs packed into the nucleus of a single cell.

Identical twins share nearly all their DNA, usually above 99.9%, with tiny differences from early cell changes.

Humans share roughly 40–60% of their genes with bananas, but only a small slice of total DNA is closely alike when entire genomes are compared.

Full siblings share about half of their dna on average, though the exact percentage can swing several points above or below that.

A child inherits about half of nuclear DNA from each parent, with small twists for sex chromosomes and mitochondrial DNA.

Most full siblings share around half of their variable DNA, with real values often landing between about 38% and 61%.

You share about 12.5% of your dna with each great grandparent, though real dna segments can range widely around that average.