XYY vs sex chromosome

XYY and sex chromosome both are nouns.

Word	Noun	Adjective	Verb	Adverb
XYY	Yes	No	No	No
sex chromosome	Yes	No	No	No

As nouns, sex chromosome is a hypernym of XYY; that is, sex chromosome is a word with a broader meaning than XYY:

XYY: (genetics) abnormal complement of sex hormones in a male who has two Y chromosomes
sex chromosome: (genetics) a chromosome that determines the sex of an individual

XYY (noun)	sex chromosome (noun)
(genetics) abnormal complement of sex hormones in a male who has two Y chromosomes	(genetics) a chromosome that determines the sex of an individual