Overview
This lecture introduces the structure and function of DNA, covering key terminology, DNA organization, building blocks, and its central roles in heredity and protein synthesis.
DNA Basics and Terminology
- DNA (deoxyribonucleic acid) is a nucleic acid that stores information to control cellular activities.
- DNA controls cell specialization, organ formation, and protein synthesis.
- DNA is located primarily in the nucleus of cells, usually as a chromatin network.
- DNA condenses into chromosomes for cell replication or repair.
- Humans have 46 chromosomes, inheriting 23 from each parent.
- Chromosomes are DNA strands wound around proteins and contain genes.
DNA Structure and Components
- DNA's shape is a double helix, discovered by Watson and Crick.
- Chromosomes consist of two identical chromatids connected by a centromere.
- Chromatids are identical to ensure accurate transmission of genetic information.
- Each chromosome has a short (p) and long (q) arm.
- DNA is packaged around histone proteins for protection and structure.
Building Blocks: Nucleotides
- Nucleotides are the monomers (building blocks) of DNA.
- Each nucleotide contains a phosphate group, a deoxyribose sugar, and a nitrogenous base.
- The four nitrogenous bases are adenine (A), thymine (T), guanine (G), and cytosine (C).
- Bases pair specifically: A with T, and G with C (complementary base pairs).
- The sugar-phosphate backbone forms the sides of the DNA ladder.
DNA Bonding and Structure Details
- Base pairs are held together by weak hydrogen bonds, allowing DNA strands to separate during replication.
- Adenine and guanine are double-ring structures called purines.
- Thymine and cytosine are single-ring structures called pyrimidines.
Functions of DNA
- DNA carries hereditary information in genes, determining characteristics like eye color or blood group.
- DNA codes for protein synthesis, providing instructions for growth and development.
- DNA must replicate to pass genetic information to the next generation during cell division.
Key Terms & Definitions
- DNA (Deoxyribonucleic acid) — molecule storing genetic information.
- Chromatin — loose form of DNA in the nucleus.
- Chromosome — condensed DNA structure visible during cell division.
- Gene — segment of DNA coding for a protein or trait.
- Nucleotide — DNA monomer with phosphate, sugar, and base.
- Double helix — spiral shape of DNA.
- Purine — double-ring nitrogen base (adenine, guanine).
- Pyrimidine — single-ring nitrogen base (thymine, cytosine).
- Histone — protein that DNA wraps around in chromosomes.
- Complementary base pair — specific pairing of A-T and G-C.
Action Items / Next Steps
- Review DNA structure diagrams, focusing on nucleotide arrangement and base pairing.
- Memorize the definitions of all key terms listed.
- Prepare for upcoming lessons on DNA replication and protein synthesis.