Gene annotation provides functional and other information, for example the location of each gene within a particular chromosome.

I can't point to a particular spot on a particular chromosome and say, 'There lies happiness. '

'Position' here means position along the length of a particular chromosome.

My work on that brought me to studying Down syndrome because those patients have an extra copy of that particular chromosome.

How could we erase a specific gene from one particular chromosome, or add one to it, or repair a single pair of nucleotides?

A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two.

Crossing-over changes which alleles sit on a particular chromosome.

A sequence of consecutive alleles on a particular chromosome is known as a haplotype.

However, it is quite feasible to determine the sequence of a defined area of a particular chromosome.

Telomeres are not a counting mechanism, though they may be used to indicate the number of times a particular chromosome has been replicated.