What Accessory to a Standard Railing Is Shown in the Diagram

question 22

Short Answer

What accessory to a standard railing is shown in the diagram and indicated by a large arrow?

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Definitions:

Substrate

The surface or material on or from which an organism lives, grows, or obtains its nourishment, or the reactant upon which an enzyme acts.

RNA Hypothesis

A scientific theory suggesting that RNA, rather than DNA, was the first genetic material to evolve in early life forms.

Polypeptides

Chains of amino acids linked by peptide bonds, which can function independently or as part of a protein.

Alexander Cairns-Smith

A scientist known for his "clay hypothesis" proposing that complex organic molecules could have evolved from clay minerals.