A: On 12 September 2001, less than 24 hours after the terrorist attacks against the United States, NATO declared the attacks to be an attack against all NATO member countries within the terms of Article 5 of the North Atlantic Treaty.
Humans have an additional pair of sex chromosomes for a total of 46 chromosomes. The sex chromosomes are referred to as X and Y, and their combination determines a personâs sex. Human females have two XX chromosomes while males possess an XY pairing.
The sex chromosomes of mammals have evolved over millions of years, originating from two identical chromosomes. Now, males possess one X and one Y chromosome and females have two Xs. The presence or absence of the Y chromosome is what determines sexâthe Y chromosome contains several genes key to testes formation. But while the X chromosome has remained large throughout evolution, with about 2000 genes, the Y chromosome lost most of its genetic material early in its evolution; it now retains less than 100 of those original genes.