During prophase I of meiosis, crossing over between the sister chromatids occurs. What is the purpose of this process? To produce genetic variation. To duplicate the DNA. To produce the spindle fibers. To remove the nuclear envelope.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

a covalent bond, specfically triple bond