Crossing-over occurs during the stage of meiosis called

Which best explains why there are 64 possible codons in the genetic code and only 20 amino acids that make protiens of living organisms on earth

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

You find a fossil that you are sure shows evidence of bipedalism. you know this because which of the following anatomical traits is present? a. thighbones that angle in toward the knees b. a narrow pelvis c. opposable hallux d. posterior position of the foramen magnum