However, when feelings of intense fear and distress are overwhelming and prevent us from doing everyday things, an anxiety disorder may be the cause. Anxiety disorders are the most common mental health concern in the United States. An estimated 40 million adults in the U.S., or 18%, have an anxiety disorder. Approximately 8% of children and teenagers experience the negative impact of an anxiety disorder at school and at home.
Sexual Reproduction: Sexual reproduction promotes genetic variation by producing different gene combinations. Meiosis is the process by which sex cells or gametes are created. Genetic variation occurs as alleles in gametes are separated and randomly united upon fertilization. The genetic recombination of genes also occurs during crossing over or the swapping of gene segments in homologous chromosomes during meiosis.
A third source of genetic diversity occurs during meiosis II, in which the sister chromatids separate and are randomly distributed to the daughter cells, the gametes. Crossing over in meiosis I leads to non-identical chromatids in meiosis II chromosomes.