3.1.5 Nucleic acids are important information-carrying molecules

Question 1

Examples of Nucleic Acids (examples of polynucleotides)

Answer 1

• Ribonucleic acid (RNA)
• Deoxyribonucleic acid (DNA)

Question 2

Components of a DNA nucleotide

Answer 2

• Deoxyribose sugar
• Phosphate group
• A nitrogen-containing base (Adenine, Thymine, Cytosine, Guanine)

Question 3

Examples of nitrogen-containing bases

Answer 3

• Adenine
• Thymine
• Uracil
• Cytosine
• Guanine

Question 4

Components of an RNA nucleotide

Answer 4

• Ribose sugar
• Phosphate group
• A nitrogen-containing base (Adenine, Uracil, Cytosine, Guanine)

Question 5

What type of bond forms between nucleotides to form what?

Answer 5

• Phosphodiester bonds, to form polynucleotides
• Condensation reaction between the phosphate and deoxyribose
• Catalysed by DNA polymerase

Question 6

Structure of RNA

Answer 6

• Single-stranded
• Short polynucleotide chain

Question 7

Structure of DNA

Answer 7

• Double-stranded (2 long strands of polynucleotides, which are joined together by hydrogen bonds between the complementary base pairs to form a double helix)

Question 8

Types of RNA

Answer 8

• mRNA
• rRNA
• tRNA

Question 9

Role of mRNA

Answer 9

transfers genetic information from DNA to ribosomes

Question 10

Role of rRNA

Answer 10

ribosomes are made up of proteins + rRNA

Question 11

Role of tRNA

Answer 11

• involved in protein synthesis transcription + translation
• bringing specific amino acids to the ribosome

Question 12

Complementary Base Pairing

Answer 12

• Adenine always pairs to Thymine (complementary)
• Cytosine always pairs to Guanine (complementary)

Question 13

Quantities of bases

Answer 13

Quantity of adenine=quantity of thymine
Quantity of guanine=quantity of cytosine

Question 14

When does DNA Replication occur?

Answer 14

S phase of interphase, which is before nuclear division and cytokinesis

Question 15

Name for DNA replication

Answer 15

Semi-conservative replication

Question 16

Process of semi-conservative replication

Answer 16

• DNA helicase unzips the DNA molecule
• DNA helicase breaks the hydrogen bonds between the complementary bases in the polynucleotide strands
• Free DNA nucleotides attach to the exposed bases on the template strands by complementary base pairing
• DNA polymerase joins the adjacent nucleotides together by a condensation reaction, and phosphodiester bonds form between them
• DNA molecule recoils

Question 17

The 2 scientists who proposed models of the chemical structure of DNA and DNA replication

Answer 17

Crick
Watson

Question 18

Why can nucleotides only be added in the 5’ to 3’ direction to the DNA strand?

Answer 18

• DNA polymerase is specific and only complementary to 5’ end of strand
• Shapes of 5’ and 3’ are different