What are the three stop codons?

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?

Which part of cellular respiration must occur before any of the other steps can occur

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point