OCR A Level Nucleic Acids

The following statements are about the structure of DNA.
Which of the following statement(s) is / are true?

• Purine bases pair with pyrimidine bases.

• Phosphodiester bonds link adjacent nucleotides.

• There are always equal amounts of adenine and guanine.

Name the base represented by the letter T.

Complete a section of the mRNA strand that is complementary to the section of the DNA strand shown.

DNA is formed from three main groups of molecules: pentose sugars, phosphate groups and nitrogenous bases. The bases can be divided into purines and pyrimidines.

Identify the two purines below.

• A

• B

• C

• D

DNA is formed from three main groups of molecules: pentose sugars, phosphate groups and nitrogenous bases. The bases can be divided into purines and pyrimidines.

Identify the two pyrimidines below.

• A

• B

• C

• D

Name the circled component in the diagram. ​ (a)  
Name the bond labelled X in the diagram. ​ ​ (b)  

• deoxyribose
• phosphodiester
• ribose
• ester
• peptide
• glycosidic

Which of the following processes involves the formation of ester bonds?

1 - synthesis of polynucleotides
2 - synthesis of triglycerides
3 - synthesis of polypeptides

• 1, 2 and 3

• Only 1 and 2

• Only 2 and 3

• Only 1

Which of the following nucleotides contains uracil?

• A

• B

• C

• D

Which statement, A to D, describes the function of DNA polymerase?

• break the hydrogen bonds between complementary bases

• make phosphodiester bonds between adjacent nucleotides

• make phosphodiester bonds between polynucleotides

• make the hydrogen bonds between complementary bases

Name the components of the circled nucleotide.

Circle:​ ​ ​ (a)  

Pentagon: ​​ (b)  

Square:​ (c)  

• Phosphate
• Deoxyribose
• Guanine
• Ribose
• Adenine
• Thymine
• Cytosine
• Glucose
• Carbohydrate
• Magnesium