15. A scientist puts nucleotide chains of into a test tube and theen allows protein synthesis to take place. Soon, the test tube is full of polypeptide chains made entirely of the amino acid phenylalanine. What does this experiment indicate? 1. that the amino acid phenylalanine is composed of uracil (U)
2. UUU codes for phenylalnine
3. protein synthesis did not occur
4. all proteins are composed of only one type of amino acid

In order to clone adult animals, scientists typically begin with a(n)

What environmental cues and landmarks do the geese use to determine the timing and direction of their migration over the mountains? how do they find their way?

Which of these is true of the cytoplasm of an unfertilized egg? a. it is an unevenly distributed mixture of mrna, proteins, organelles, and other substances. b. it does not contain substances that are important in directing development. c. these substances are supplied by the sperm. d. it does not contain substances that are important in directing development. e. development is directed solely by the surrounding cells. f. it is a homogeneous mixture of mrna, proteins, organelles, and other substances. g. it does not contain substances that are important in directing development. h. these substances are produced by the dna of the fertilized zygote.