The Make-up of DNA

Question 1

What is the structure of a DNA molecule?

Answer 1

• a long chain (polymer) made up of small units (monomers) called nucleotides

Question 2

What is each nucleotide made up of?

Answer 2

• sugar molecule - deoxyribose (S)
• phosphate molecule (P)
• nitrogenous base

Question 3

What are the different kinds of nitrogenous bases?

Answer 3

• adenine (A)
• thymine (T)
• guanine (G)
• cytosine (C)

Question 4

What do the four nitrogenous bases do?

Answer 4

• foundation of the genetic code
• instructing cells on how to synthesise enzymes and other proteins

Question 5

How are the outer two strands of the double helix made up?

Answer 5

• formed by a chain of alternating sugar/phosphate links
• the bonds between the sugar and phosphate molecules are strong

Question 6

How are the inner rungs of the ladder of the double helix made up?

Answer 6

• formed from pairs of bases linked by weak hydrogen bonds

Question 7

What are the base pairs attached to in the double helix?

Answer 7

• base pairs are attached to the sugar molecules

Question 8

What are the two groups of nitrogenous bases?

Answer 8

• purines
• pyrimidines

Question 9

What are purines made up of?

Answer 9

• two fused rings of nitrogen, carbon and hydrogen atoms
• e.g. guanine and adenine

Question 10

What are pyrimidines made up of?

Answer 10

• one ring of similar atoms (therefore much smaller than purines)
• e.g. thymine, cytosine and uracil

Question 11

What is a base pair always made up of?

Answer 11

• one purine and one pyrimidine

Question 12

What makes the difference in DNA structures of different organisms?

Answer 12

• the sequence in which the nucleotides are strung together

Question 13

What determines the genetic code of an organism?

Answer 13

• the sequence of the nucleotides