Red-green color blindness is a human X-linked recessive disorder. A young man with a 47,XXY karyotype (klinefelter syndrome) is color blind. His 46,XY brother also is color blind. Both parents have normal color vision. Where did the nondisjunction occur that gave rise to the young man with Klinefelter syndrome?

The non-dis-junction occur with Klinefelter syndrome  is occurred at "Meiosis II;Mother"

Explanation:

Thus, the more likely than not acquired the Y chromosome from his dad who has typical shading vision, there is no chance for a nondisjunction occasion to have occurred from the fatherly heredity. His mom must be heterozygous in light of the fact that she has typical shading vision. This implies she more likely than not acquired a visually challenged X chromosome from her partially blind dad.  

For him to acquire two partially blind X chromosomes from his mom, the egg more likely than not been the result of a non-dis-junction in meiosis II.  

In meiosis I, the homologous X chromosomes independent, so one cell has the and different has . Disappointment of sister chromatids to isolate inmeiosis II would then bring about an egg with two duplicates of Xc.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs