2.1.3 - Nucleotides & Nucleic Acids Flashcards
General structure of a nucleotide
- Nitrogenous base
- Pentose sugar
- Phosphate
Pyrimidine = 1 nitrogenous base
Purine = 2 nitrogenous bases
Difference between RNA and DNA nucleotides
Pentose sugar; Ribose in RNA, Deoxyribose in DNA
Nitrogenous base; in RNA U replaces T
Formation of a polynucleotide
Condensation reaction between the phosphate group and pentode sugar; forms a 3’ to 5’ phosphodiester bond
- Broken via hydrolysis
Structure of ATP
- Adenine base
- 3 Phosphate groups
- Ribose sugar
DNA Structure
- Two anti-parallel strands (3’ to 5’ and 5’ to 3’) twist around to form a double helix
- Strands are held together via hydrogen bonds between complementary base pairs
C - G: 3 hydrogen bonds
A - T: 2 hydrogen bonds
- Purine binds with pyrimidine
DNA replication: Step 1
- DNA replicates during interphase
- The enzyme helicase breaks hydrogen bond between the bases
- The double helix unwinds/uncoils
- Each strand acts as a template
DNA replication: Step 2
- Free nucleotides from the cytoplasm assemble on the template DNA in complementary base pairs
DNA replication: Step 3
- Hydrogen bonds reform between bases
- The enzyme DNA polymerase joins the nucleotides, forming a new sugar-phosphate backbone
- Two identical DNA molecules have been produced
What does semi-conservative replication mean?
- DNA replication is semi conservative a each new DNA molecule contain one of the old strand and one of the new strands
Why is semi-conservative replication useful?
- Accurately conserves genetic material
- Lowers the occurrence of spontaneous mutations
What is a gene?
A section of DNA that codes for the sequence of amino acids in a polypeptide
- Alleles are different versions of a gene