Biological Molecules - Nucleic Acids

Question 1

What are the contents of DNA nucleotides?

Answer 1

• A phosphate group
• A pentose sugar (deoxyribose)
• A nitrogenous base (A,C,G,T)

Question 2

What is the formation of DNA?

Answer 2

• Nucleotides join together from the 3rd carbon on the pentose sugar to the phosphate group
• This is a phosphodiester bond
• Water is removed in a condensation reaction
• Continued condensation reactions form a polynucleotide

Question 3

What is the structure of DNA?

Answer 3

• Antiparallel strands
• 5’ and 3’ ends
• Complementary base pairing
• Sugar phosphate backbone
• C-G bonding (3 hydrogen bonds)
• A-T bonding (2 hydrogen bonds)

Question 4

What are the contents of RNA nucleotides?

Answer 4

• A phosphate group
• A pentose sugare (ribose)
• A nitrogenous base (A,C,G,U)

Question 5

What is the structure of RNA?

Answer 5

• Single stranded
• Shorter than DNA
• Less stable than DNA
• 3 forms: mRNA, tRNA and rRNA

Question 6

The bases can be split into 2 types. Why?

Answer 6

• Adenine and Guanine are double-ring structures: Purines
• Cytosine and Thymine are single-ring structures: Pyrimidine

Question 7

What are the functions of DNA?

Answer 7

• Passes on genetic information from cell to cell (mitosis) and generation to generation (meiosis)
• About 3.2 billion bases in 1 mammalian cell and therefore an infinity variety of sequences
• This variety widens the gene pool, providing diversity within living organisms

Question 8

What is semi-conservative replication of DNA?

Answer 8

• Ensures genetic continuity between generations of cells meaning that genetic information is passed on from one generation from the next

Question 9

What are the stages if semi-conservative replication?

Answer 9

• An enzyme, helicase, breaks hydrogen bonds to separate the two strands of DNA
• Both strands act as a template
• Free nucleotides line up with exposed bases. This is complementary base pairing
• DNA polymerase forms phosphodiester bonds between adjacent nucleotides (works in 5’ –> 3’ direction only)
• DNA ligase joins fragments together
• Semi-conservative replication. Each new DNA molecule is made of 1 new and 1 orignal strand