Answer:
DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C). The order of these bases is what determines DNA's instructions, or genetic code.
Explanation:
The best estimate for Earth's age is based on radiometric dating of fragments from the Canyon Diablo iron meteorite. From the fragments, scientist calculated the relative abundances of elements that formed as radioactive uranium decayed over billions of years.
Limestone is composed largely of the minerals calcite or aragonite. Some limestones do not consist of grains and are formed by the chemical precipitation of calcite or aragonite. This is how limestone can be classified as chemical.
Answer:
This is an incomplete question.
Below should be the complete one with options:
A researcher introduces a signal produced by bacteria to eukaryotic cells that she is culturing in the laboratory. Remarkably, she notices that this signal results in an increase in eukaryotic gene expression. How is this possible?
A.This gene expression is likely independent of the presence of the prokaryotic signal.
B.The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.
C.This signaling pathway might actually be utilized by both prokaryotes and eukaryotes.
D.This signal is likely similar in structure to ligands utilized by eukaryotic cells.
E.This prokaryotic signal likely travels directly into eukaryotic cells and acts as a transcription factor.
THE CORRECT ANSWER IS B
B.The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.
