An eager grad student attempted the famous Meselson and Stahl experiment with a twist. She first grew E. coli in media containing 'light' 14N isotopes which the bacteria incorporated into their DNA. She then switched to 'heavy' media containing 15N isotopes and grew the bacteria for 2 generations. She then switched back to media containing 14N isotopes and grew the bacteria for 1 more generation. She isolated the DNA and analyzed the molar ratios of 15N:15N DNA, 15N:14N hybrid DNA, and 14N:14N DNA by centrifugation. Assuming semi-conservative replication, the expected molar ratios are: Group of answer choices

in 1972 the fluid—mosaic membrane model of membrane structure was proposed based on thermodynamic principals of organization of membrane lipids and proteins and available evidence of asymmetry and lateral mobility within the membrane matrix [s. j. singer and g. l. nicolson, science 175 (1972) 720–731].

it cools slower in the earth meaning the crystals have more time to form than lava on the surface

hey, i believe your answer would be d. sugar ribose and the base uracil. i believe this is the answer, because rna consists of sugar ribose, adenine, guanine, cytosine, and uracil.

your first option is incorrect, because that's dna. where it consists of sugar deoxyribose, adenine, guanine, cytosine and thymine.

your second option is also incorrect, this is because sugar deoxyribose is in dna, and uracil is in rna. these two do not make sense together.

your third option being incorrect, because sugar ribose is in rna, but not the base of thymine. rna consists of uracil, not thymine.

lastly your fourth option being correct! this answer is correct, because both sugar ribose, and the base uracil are in rna! ~

answer is d. sugar ribose and the base uracil.