Nucleic Acids A-level OCR

Which of the following bonds are broken during DNA replication?

• hydrogen bonds between bases
• phosphodiester bonds
• covalent bonds between bases
• ionic bonds between bases and phosphate groups

Which base is not found in RNA?

• adenine
• cytosine
• thymine
• uracil

How many base pairs are there in one full turn of the DNA double helix?

• 4
• 10
• 16
• 64

Analysis of a sample of DNA found that 20% of the bases were adenine. What percentage of the bases are pyrimidines?

• 20%

• 30%

• 60%

• 50%

Which technique was used to determine the double-helical structure of DNA?

• electrophoresis
• chromatography
• centrifugation
• X-ray crystallography

Analysis of a molecule of DNA found it to contain 200 adenine bases, 20% of the total number of bases in the strand. How many phosphate groups did it contain?

• 200
• 400
• 800
• 1000

Which of the following options, A – D, are the pyrimidine bases found in DNA?

• uracil and thymine
• thymine and cytosine
• adenine and thymine
• cytosine and uracil

If 30% of the bases in a DNA molecule are adenine, what percentage of the bases are guanine?

• 20%

• 30%

• 35%

• 70%

Thymine comprised 36% of the nitrogen bases present in a sample of double stranded DNA. What was the percentage of guanine in the sample?

• 14%

• 28%

• 36%

• 64%

A piece of DNA was analysed and 15% of its nucleotides were adenine. What percentage would be uracil?

• 0

• 15%

• 30%

• 35%