Why is the frequency of recombinant gametes always half the frequency of crossing over?

Abnormal softening of a gland is known as

How does deforestation affect the water cycle? a. it increases the amount of runoff b.it increases the amount of percolation c. it increases the amount of transpiration d. it increases the amount of precipitationa it increases the amount of runoff

Aboy jumps into a cold swimming pool and his body tempature goes down hus muscles ,blood vessels