for crossing over to occur, homologous chromosomes must align precisely early in prophase i so that nonsister chromatids can exchange corresponding segments of dna.

What are the two causes of density in deep current waters? a. salinity (how much salt) of the water and high temperaturesb. salinity (how much salt) of the water and low temperatures c. oxygen content of the water and high temperatures. d. oxygen content of the water and low temperatures