DNA - RNA

exercises

The diagram on the right represents a nucleotide with subunits X,Y and Z.

This nucleotide could be a monomer of DNA but not RNA if:
Z is ribose; Y is thymine; Y is phosphate; Y paired with cytosine.

Which comment is true for this structure?

This is known as an DNA strand. This is known as an RNA strand. This is a nucleotide found in DNA. This is a nucleotide found in RNA.

Which comment below is true?

Structure A can be found in RNA. Structure A can be found in DNA. Structure A forms the monomers of a protein. Structure A is formed from 4 subunits. Sugar is not part of structure A.

What is the reason why structure B is not found in DNA.

It contains a deoxyribose sugar unit. It contains a phosphate group. It contains the base uracil. It is only made up of three subunits. It can not increase in length through polymerisation.

Which comment is true?

Uracil can link to a deoxyribose sugar. Phosphate can not link to a sugar unit. Uracil can not link to a deoxyribose sugar. Uracil can not link to a ribose sugar.

Uracil is one of the bases found in a nucleotide polymer. Which comment is true?

This polymer does not contain phosphate. This polymer contains two phosphate groups for every uracil present. This polymer must contain a ribose sugar unit.

The structure shown on the right was isolated from an organic molecule. Which comment below is true?

The molecule was the start of an RNA strand. The molecule was a protein. The molecule was the terminal section of an RNA strand. The molecule was most likely DNA.

Consider the two double stranded DNA fragments on the right. C is for cytosine, G is for guanine, T is for thymine and A is for adenine. When heated, the strands begin to separate. Which comment below is true?

Both fragments will separate at the same temperature. Strand Y will separate at a higher temperature than fragment X Strand X will separate at a higher temperature than fragment Y

How many water molecules are required to hydrolyse fragment X into its constituent nucleotides?

14 15 16 9 18

Solution

Consider the two DNA fragments above. Which comment is true?

Fragment X has a higher degree of hydrogen bonding holding the two strands together than fragment Y. Fragment Y has a higher degree of hydrogen bonding holding the two strands together than fragment X. The strands in both fragments are held together by strong covalent bonds.