Most Active Galactic Nuclei Are at Large Distances from Us;

question 44

Multiple Choice

Most active galactic nuclei are at large distances from us; relatively few nearby galaxies harbor active galactic nuclei. What does this imply?

• A)Active galactic nuclei can form only at large distances from the Milky Way.
• B)Massive black holes existed only when the universe was young and no longer exist today.
• C)Active galactic nuclei tend to become less active as they age.
• D)The jets seen in many active galactic nuclei must cause them to move far away from us.

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Definitions:

Taq Polymerase

An enzyme derived from the bacterium Thermus aquaticus, used in PCR to amplify DNA sequences.

DNA Sequences

The order of nucleotides in a strand of DNA, which determines the genetic information carried by that DNA.

Gene Targeting

A genetic technique that uses homologous recombination to change an endogenous gene's sequence to study gene function or create specific animal models for human disease.

Knock-Out Gene

A gene that has been deliberately inactivated or deleted through genetic engineering to study its function by observing the resulting phenotype.