How does random fertilization add to the genetic variation?
a)nonsister chromatids exchange gene segments to produce new combinations of maternal and paternal genes.
b)fusion of sperm and ovum, each having a unique combination of chromosomes, introduces further variation.
c)homologous pairs of chromosomes sort into daughter cells independently of the other pairs.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Which genetic disorders, caused by an extra x chromosome (xxy), is characterized by a lack of testicular development in males, effeminate features, possible mental impairment, and a thin stature?

Physical characteristics of down syndrome