Final answer:
Most males with an extra Y chromosome are tall and normal with regard to their physical characteristics and behavior. XYY syndrome does not predispose individuals to violence or anti-social behavior. Other chromosomal conditions like Klinefelter and Turner syndrome have more pronounced effects on health and physiology.
Step-by-step explanation:
Most males born with an extra Y chromosome are tall but are otherwise normal, which matches with option C. This condition is known as XYY syndrome or Jacob's syndrome. Despite some early studies that suggested a correlation between the XYY karyotype and aggressive behavior, this has been largely debunked by more extensive and controlled studies. It is now understood that XYY males may be taller than average and have an increased risk for learning difficulties and speech delays, but they do not show a predisposition to violent or anti-social behavior.
Contrary to the myth, XYY males are neither more aggressive nor do they tend to become violent criminals. They are phenotypically male, with the presence of the Y chromosome triggering the development of male characteristics. In most cases, those with an extra Y chromosome can lead normal lives and the variance often goes undetected.
It's important to note that other chromosomal conditions such as Klinefelter syndrome (XXY) and Turner syndrome (XO) present with more pronounced physical characteristics and health challenges. Each additional X chromosome is inactivated to some extent, as seen in various Barr bodies within the cell nuclei, but this inactivation doesn't negate all the effects of the extra chromosomes.