Identify the correct spelling of the term chromosomal “three copies”.

The correct answer is Trisomy.

Explanation:

The term referring to the presence of an extra chromosome in a cell (i.e., having "three copies" of a particular chromosome instead of the usual pair) is spelled Trisomy.

It is derived from the prefix "tri-" (meaning three) and "somy" (referring to chromosomes, as in chromosome or autosome). Common genetic conditions associated with trisomy include Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), and Trisomy 13 (Patau syndrome).

Let's look at the options provided:

• Trissomie - Incorrect spelling (contains an extra 's' and ends in 'ie').
• Trissomy - Incorrect spelling (contains an extra 's').
• Trisomy - Correct spelling.
• Trisomie - Incorrect spelling (French spelling, not standard English).