Question

The backbones of DNA and RNA are

A. identical.
B. very different, made of nucleotides in DNA and amino acids in RNA.
C. made of alternating sugars and phosphate groups.
D. made of a chain of base pairs.

Answer 1

Answer:

The answer is very likely C.

Explanation:

This becomes easy once we remember that DNA and RNA are not identical - which is why they have different names, RNA = 'ribo', DNA = 'deoxy.' This eliminates choice (A).  While they are different, they are not incredibly different - DNA and RNA are both made up of nucleotides - they are not however, made up of Amino acids. Amino acids are what they can code for, and subsequently create proteins during protein synthesis. This helps us eliminate (B). Finally, we know that in order for something to have base pairs it needs to be double stranded - which RNA is not. Which means that because RNA is not double stranded (its singly stranded) that the answer cannot be (D). Leaving us with the only plausible option; (C).

Answer 2

Answer:

In the 1950s, Francis Crick and James Watson worked together at the University of Cambridge, England, to determine the structure of DNA. Other scientists, such as Linus Pauling and Maurice Wilkins, were also actively exploring this field. Pauling had discovered the secondary structure of proteins using X-ray crystallography. X-ray crystallography is a method for investigating molecular structure by observing the patterns formed by X-rays shot through a crystal of the substance. The patterns give important information about the structure of the molecule of interest. In Wilkins’ lab, researcher Rosalind Franklin was using X-ray crystallography to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule using Franklin’s data (Figure 9.2). Watson and Crick also had key pieces of information available from other researchers such as Chargaff’s rules. Chargaff had shown that of the four kinds of monomers (nucleotides) present in a DNA molecule, two types were always present in equal amounts and the remaining two types were also always present in equal amounts. This meant they were always paired in some way. In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine for their work in determining the structure of DNA.