DNA Structure and Function in Heredity

Introduction to DNA as the Molecular Basis of Heredity

• DNA is structured as a double helix, resembling a twisted ladder.
• Acts as the molecular basis for heredity.
• DNA molecules can be tens of millions of base pairs long.

DNA Replication

• Essential for genetic material to be replicated during cell division.
• Process called replication:
  • DNA strands act as templates to create two identical DNA molecules.
  • A base pairs with T, and C pairs with G in DNA.

Expression of Genes

• Replication alone is not sufficient; genes need to be expressed.
• Expression involves coding for proteins that define organism traits.

Key Terminology

• DNA: Molecule with sugar-phosphate backbone and base pairs.
• Chromosome: DNA packaged with proteins.
• Gene: Section of DNA coding for a protein or trait.
• RNA: Ribonucleic acid, related to DNA.

Role of RNA in Gene Expression

• RNA serves as a messenger from DNA to the site of protein synthesis.
• Transcription: Process of creating mRNA (messenger RNA) from DNA.
  • A pairs with U (uracil) in RNA; C still pairs with G.

Protein Synthesis

• mRNA carries genetic information from DNA out of the nucleus.
• Translation: Process of converting mRNA sequence into an amino acid sequence.
  • Involves ribosomes and tRNA (transfer RNA) matching codons.
  • Each set of 3 bases on mRNA, known as a codon, codes for an amino acid.
  • There are 64 possible codons for 20 amino acids.

Function of Proteins

• Proteins are sequences of amino acids, forming complex structures.
• Perform various functions in organisms, e.g., enzymes, structural components, etc.
• Essential for the operational and structural elements of life.