DNA Structure and Function

Overview

• Focus: Structure of DNA, nucleotides, complementary base pairing.
• Gene Function: Brief explanation of how genes code for proteins.

DNA Structure

• DNA consists of two strands in a twisting double helix.
• Each strand can be visualized in a 2D diagram as if untwisted.

Nucleotides

• DNA is a polymer made up of monomers called nucleotides.
• Each nucleotide consists of:
  • Phosphate group
  • Sugar
  • Base (one of four types: A, T, C, G)
• Four types of nucleotides correspond to the four bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

Formation of DNA Strand

• Phosphate of one nucleotide bonds to the sugar of the next.
• Forms a long chain: Sugar-Phosphate Backbone.
• Bases stick out to the side, allowing for strand pairing.

Complementary Base Pairing

• Two DNA strands run in opposite directions and pair via bases.
• Complementary Pairs: A pairs with T, C pairs with G.
• Allows determination of complementary sequences:
  • Example: For sequence AGT GCT TAC, the complementary is TCA CGA ATG.

Genetic Code and Proteins

• Genetic Code: Sequence of bases in DNA.
• Gene: A sequence that codes for a protein.
  • Each three bases (triplet) codes for an amino acid.
  • Example: AGT codes for one amino acid, GCT for another.

Protein Formation

• Cells read DNA sequences in triplets to determine amino acids.
• Amino acids are combined in order to form a protein.
• Proteins fold into unique shapes which determine their functions.

Functions of Proteins

• Enzymes: Biological catalysts that speed up chemical reactions.
• Hormones: Carry messages throughout the body.
• Structural Proteins: Provide strength to cells and tissues.

• Conclusion: The session provided an understanding of DNA's structure and function, and how genes encode proteins.