DNA Structure & Replication

DNA: Structure & Replication

• DNA controls all cell activities
• Found in the nucleus of eukaryotic cells
• Found in the cytoplasm of prokaryotic cells (bacteria)
• DNA is an abbreviation for Deoxyribonucleic Acid
• DNA is a nucleic acid, one of the four biomolecules
• DNA is made of smaller building blocks called nucleotides
• Nucleotides have three parts:
  • Deoxyribose sugar (a pentagon-shaped 5-carbon sugar)
  • Phosphate group
  • Nitrogenous base
• There are four types of nitrogenous bases:
  • Thymine (T)
  • Adenine (A)
  • Cytosine (C)
  • Guanine (G)

Simple Nucleotide Structure

• Nucleotides consist of a phosphate group attached to a sugar molecule, which is then attached to a nitrogenous base

DNA Structure

• Nucleotides bond together to form the DNA molecule
• DNA has a double helix shape, resembling a spiral staircase
• When unwound, DNA looks like a ladder
• The "rails" or "backbone" of the ladder are alternating sugar and phosphate molecules
• The "rungs" or "steps" of the ladder are complementary pairs of nitrogenous bases
• Nitrogenous bases are held together by hydrogen bonds
• These hydrogen bonds can be easily broken for replication

Complementary Nitrogen - Base Pairing

• Nitrogenous bases bond in a specific manner:
  • Adenine (A) bonds with Thymine (T)
  • Cytosine (C) bonds with Guanine (G)
• This is known as Chargaff's rule
• Each side of the DNA ladder (strand) is antiparallel to the other

DNA Replication

• DNA must be copied for cell division, through a process called replication.
• Replication occurs during the S-phase of interphase
• Enzymes are essential for replication
• Key enzymes for Replication are:
  • Helicase (unzips the DNA)
  • Polymerase (adds new complementary nucleotides)
• Replication results in two identical DNA molecules
• Each new DNA molecule has one old strand and one new strand

Explore the foundational concepts of DNA, including its structure, replication process, and components. This quiz covers the basic building blocks of DNA and how they combine to form the double helix. Test your knowledge on nucleotides, nitrogenous bases, and the biological significance of DNA.