DNA: code of life

Introduction
- Review of Cell Structure
  - Focus on ribosome, cytoplasm, and nucleus components.
Nucleic Acids
- Types:
  - DNA (Deoxyribonucleic acid)
  - RNA (Ribonucleic acid)
- Composed of nucleotides (monomers):
  - DNA nucleotides in nucleoplasm used for DNA synthesis.
  - RNA nucleotides: mRNA in nucleoplasm, tRNA in cytoplasm.
Chromosomes
- Types: unreplicated and replicated.
- Structure relates to cell cycle.
Key Terms
- DNA, RNA, Nucleic Acids, Mitochondrial DNA (mtDNA), Centromere, Double Helix, Histones.
- Genes: Section of DNA coding for a protein; 1 gene = 1 protein.
- Homologous Chromosomes: Chromosomes of same size and shape.
- Chromosomes in Meiosis: Important feature to note.
- Definitions from the Diagnostic Report:
  - Chromosome: DNA structure comprising genes, visible during cell division.
  - Centrosome: Structure that forms spindle fibers from two centrioles in animal cells.
  - Centromere: Joins chromatids in replicated chromosomes.
  - Centriole: Pair of structures aiding spindle thread formation.
  - Chromatin: Non-dividing DNA network in interphase cells.
  - Chromatid: Half a chromosome, contains genetic information.

Location
- Nuclear DNA: Present in the nucleus.
- Mitochondrial DNA (mtDNA): Found in mitochondria; referred to as extra-nuclear DNA.
- Chloroplast DNA: Present in plants.
Structure of DNA
- History: Key figures such as Watson, Crick, Franklin, Wilkins (ensure to note dates and Nobel Prize details).
- Composition:
  - Made of two strands forming a double helix.
  - Each strand consists of DNA nucleotides, which include:
    - Components:
      - Phosphate group
      - Deoxyribose sugar
      - Nitrogenous base (A, T, C, G)
  - Base Pairing:
    - A-T and G-C pairing via hydrogen bonds.
Functions of DNA
- Composes genes carrying hereditary information.
- Encodes instructions for protein synthesis.

Timing in Cell Cycle
- Occurs at the end of interphase, right before cell division.
Location
- Takes place in the nucleus.
Process of DNA Replication
- Steps:
  1. Weak hydrogen bonds break, unwinding the double helix.
  2. DNA strands unzip to form separate strands.
  3. Each strand serves as a template for complementary strand formation using free nucleotides.
  4. Result: Two identical DNA molecules, each with one original and one new strand.
  5. Each DNA molecule rewinds into a double helix configuration.
Significance:
- DNA is duplicated to ensure genetic consistency in daughter cells during mitosis.

Structure of RNA
- Single-stranded molecule made of RNA nucleotides.
- Components:
  - Nitrogenous base (A, U, C, G)
  - Ribose sugar
  - Phosphate group
- Types of RNA:
  - mRNA: Straight structure
  - tRNA: Cloverleaf or three-leaf shape
Function of RNA
- Involves protein synthesis:
  - mRNA transcribes coded message from DNA in the nucleus.
  - Moves to ribosome for protein formation.
  - mRNA guides formation of amino acids using the base sequence.
  - tRNA: Brings the specific amino acids to the ribosome matching its anticodon to mRNA codons.

Transcription
- Process:
  - DNA unwinds and strands separate.
  - One strand used as a template to form mRNA with RNA nucleotides from nucleoplasm.
  - mRNA carries the genetic code for protein synthesis.
Translation
- Process:
  - Each tRNA carries an amino acid.
  - Anticodon matches mRNA codon, bringing the necessary amino acid to the ribosome.
  - Amino acids join by peptide bonds to form proteins.
Note: Do not memorize specific codons, anticodons, or corresponding amino acids.