Chapter 2 - Nucleic Acid

Nucleoacids include both ribonucleic acid (RNA) and deoxuribonucleic acid (DNA)

Nucleotide Structure

• A pentose sugar
• A phosphate group
• A nitrogen-containing organic base - cytosine, thymine, uracil, adenine and guanine
• Joined together by a condensation reaction to form a mononucleotide
• Phosphodiester bonds forms between two nucleotides to form a dinucleotide, or a polynucleotide

RNA Structure 

• Pentose sugar is always ribose
• Organic bases are always adenine, guanine, cytosine or uracil
• One type of RNA transfers genetic information from DNA to ribosomes, another is involved in protein synthesis

DNA Structure 

• Pentose sugar is deoxyribose
• Organic bases are always adenine, guanine, cytosine or thymine
• Made up of two strands of polynucleotides and have hydrogen bonds between certain bonds, holding the strands together
• Adenine always pairs with thymine
• Guanine always pairs with cytosine
• These pairings are said to be complementary

Stability and Function of DNA

• Phosphodiester backbone protects the more chemically reactive bases
• Hydrogen bonds make the structure stronger
• Used for passing genetic information on
• Base pairing leads to DNA being able to replicate and to transfer information as mRNA

DNA Replication

• Cell division occurs in two main stages
• Nuclear division is where the nucleous divides - either by mitosis or meiosis
• Cytokinesis is where the whole cell divides
• DNA has to be replicated first, can be seen from the semi-conservative model

Semi-Conservative Replication…