How are blood and variations of traits related?

Hypertension is a complex trait with multiple environmental and genetic contributors. Linkage studies of rare Mendelian disorders of hypertension and hypotension have produced the most notable progress toward understanding the heritable basis of blood pressure. Association studies to identify common variants have been limited in the past by small sample sizes and most findings lack replication.

Icant be totally sure but i would say with confidence that it is example #1 about cells.

Ithink you should go back and learn in school rather then here asking questions