A1.2 - Nucleic acids exam style questions

Explain how the two strands of the DNA double helix are held together. (2)

• Complementary base pairs

• Hydrogen bonding between nucleotides

Distinguish between the structures of DNA and RNA (3)

• DNA is double-stranded RNA is single-stranded

• DNA contains deoxyribonucleic sugar and RNA contains ribonucleic sugar

• DNA contains Adenine, thymine, cytosine, and guanine. However, RNA contains all that except for thymine. It replaces it with uracil.

A molecule of DNA is found to contain 200 guanine bases, representing 25 % of the total number of bases. How many phosphate groups does this molecule of DNA contain?

A) 50

B) 200

C) 800

D) 1000

C

What is common to RNA and DNA?

A) Thymine

B) Nitrogenous bases

C) Histones

D) Deoxyribose

B

Nucleic acids are polymers of nucleotides. What parts of nucleotides are joined together in both DNA and RNA to make these polymers?

A) Large nitrogenous bases with small nitrogenous bases

B) Nitrogenous bases with hexose sugars

C) Nitrogenous bases with phosphates

D) Pentose sugars with phosphates

D

What is a similarity between DNA and RNA?

A) Both are polymers of nucleotides.

B) Both are composed of antiparallel strands.

C) Both contain adenine, cytosine and thymine.

D) Both contain ribose sugar.

A

For which discovery about DNA do Watson and Crick receive credit?

A) DNA is the molecule that genes are made of.

B) The amount of adenine equals the amount of thymine in an organism.

C) Phosphate–pentose bonding along the nucleotide backbone is covalent.

D) The shape of DNA is a double helix.

D

The hydrolysis of a pure sample of an organic molecule produces a pentose sugar, thymine, guanine and cytosine. What other substances could be expected to be present in the hydrolysed sample?

A) RNA

B) Uracil

C) Phosphate

D) ATP

C

Which of the following processes is most directly involved in the formation of nucleic acids such as DNA?

A. Hydrolysis

B. Condensation

C. Catabolism

D. Translation

B

Describe the structure of the DNA double helix. (8)

• complementary base pairing between nitrogenous bases

• A pairs up with T AND C pairs up with G

• two strands are antiparallel

• strands are twisted

• nucleotides consist of one phosphate group, one deoxyribose sugar and one nitrogenous base

• covalent bond between phosphate and the sugar

• Both strands are held together by hydrogen bonds

• phosphate group is bound to the 5’ carbon of the sugar

Explain how the variation in base sequences leads to the ability of DNA to have an enormous capacity for storing genetic information. (4)

• Complementary base pairing

• mutations introduce new genetic information

• DNA molecules are very long

• genetic code is stored in the sequence of nitrogenous bases

DNA is a polymer of nucleotides. Describe the structure of DNA. (7)

• DNA is a double helix

• ​two strands are antiparallel

• strands are twisted

• nucleotides consist of one phosphate group, one deoxyribose sugar and one nitrogenous base

• covalent bond between phosphate and the sugar

• two strands are held together by hydrogen bonds between nitrogen bases of two nucleotides

• ​ A pairs up with T AND C pairs up with G

Suggest one possible problem that could arise if DNA consisted of two parallel strands instead of two antiparallel strands. (1)

• No hydrogen bonding between base pairs

State one place where DNA is found in cells. (1)

Nucleus