2.5 DNA and RNA structure

Question 1

What is the structure of a DNA mononucleotide?

Answer 1

• Deoxyribose sugar with H at the 2’ position
• Phosphate group
• 1 of 4 nitrogenous bases (ATCG)

Question 2

What is the structure of a RNA nucleotide?

Answer 2

• Ribose sugar with an OH group at the 2’ position
• Phosphate group
• 1 of 4 nitrogenous bases (AUCG)

Question 3

How do nucleotides form DNA/RNA?

Answer 3

• DNA/RNA are polymers, so they are polynucleotides
• Separate nucleotides are joined via condensation reactions

Question 4

How is a phosphodiester bond formed?

Answer 4

• Condensation reactions occur between the phosphate group and the pentose sugar
• The covalent bond formed between the phosphate group and the 2 ester bonds connecting to the pentose sugars

Multiple phosphodiester bonds produce a sugar-phosphate backbone

Question 5

What is the structure of DNA polynucleotide strands?

Answer 5

• DNA is a double helix made of 2 polynucelotide strands lying anti parallel
• Each DNA strand is made of DEOXYRIBOSE (sugar) and PHOSPHATE GROUPS - this makes sugar-phosphate backbone

Question 6

Explain what antiparallel strands are?

Answer 6

• Polynucleotide strand is said to have a 3’ end and a 5’ end
• The other strand is in the opposite direction from 5’ to 3’ end

Question 7

How does hydrogen bonding contribute to the DNA backbone?

Answer 7

• Antiparallel strands have complementary base pairing that is held with H bonds

Question 8

What is the difference between phospodiester bonds and H bonds?

Answer 8

PB joins nucleotides in sugar-phosphate backbone
HB joins bases of 2 complementary strands together

Question 9

Mention how RNA structure is similar to DNA structure

Answer 9

• They are both polynucleotides
• Both contain niteogenous bases

Question 10

Mention the difference of RNA and DNA structure

Answer 10

• No thymine, RNA has Uracil
• Pentose sugar ribose instead of deoxyribose
• Single strand structure, not double helix