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.
Mammals and Drosophila females have two X chromosomes: XX males have one X chromosome and one Y: XY These are the  sex chromosomes , all other chromosomes are called  autosomes . The sex with two different chromosomes is the heterogametic sex. The other is the homogametic sex. For the X chromosome then, female mammals and Drosophila have two copies of each gene on the X, but males have only one. Females can be homozygous or heterozygous, but males are hemizygous.