You cannot even reliably determine a donor's hair color, from a single sperm cell.
I imagine it's much more difficult to reconstruct a full genome from a sperm donation than from, say, saliva on a discarded cup.
A sperm cell contains one complete haploid genome.
But (my bio is rusty) a haploid genome (gamete) cannot fully represent the genome of a diploid human.
If you're looking for genetic disorders, these will often be the result of recessive traits, right? So having only half of the chromosome sets is not indicative.
That's my example of hair color. With a full genome sequence, you could determine the person's hair color, but with a haploid genome, you could not.
If OP's joke is about the privacy implications of sperm donation, then saliva seems more risky.
Correct; my broader point was that when most people refer to a "human genome" it is ambiguous whether they mean diploid or haploid unless specified. Metrics like "3 billion base pairs" etc. actually describe the haploid human genome.
> If you're looking for genetic disorders, these will often be the result of recessive traits, right? So having only half of the chromosome sets is not indicative.
Often, but not always; there are myriad autosomal dominant disorders, as well as sex-linked disorders which require only a single mutant allele on X
> If OP's joke is about the privacy implications of sperm donation, then saliva seems more risky.
Here I think both with STR and SNP profiling you are equally at risk (i.e., saliva is not more risky)
* This I think indicates some other genetic and/or environmental factors we don't have a good grasp of.
Think about it. Each sperm cell gets a random mix of your chromosome sets. There are 2^23 possibilities.
But of course you only need to find the matched pair for each chromosome. So you'd only need a few hundred cells.
I'm not a geneticist, but that sounds like a much harder genome sequencing/assembly problem than the fully matched set you'd get from saliva etc.