DNA Replication Process

DNA Replication

• Process by which a cell makes an exact copy of its DNA before cell division
• Semi-conservative: each new DNA molecule contains one old strand (template) and one new strand
• Steps:
  1. Initiation: unwinding of DNA, binding of replication fork
  2. Unwinding: helicase unwinds DNA, topoisomerase relieves tension
  3. Binding: primase adds RNA primers to template strands
  4. Elongation: DNA polymerase adds nucleotides to primers
  5. Proofreading: DNA polymerase checks for errors
  6. Ligation: DNA ligase seals gaps between nucleotides

Gene Expression

• Process by which information in DNA is used to synthesize a functional product
• Central Dogma: DNA → RNA → Protein
• Transcription:
  • Initiation: RNA polymerase binds to promoter region
  • Elongation: RNA polymerase adds nucleotides to mRNA
  • Termination: transcription stops, mRNA is released
• Translation:
  • Initiation: ribosome binds to mRNA
  • Elongation: amino acids are added to polypeptide chain
  • Termination: protein synthesis stops, polypeptide is released

Protein Synthesis

• Process by which a polypeptide chain is synthesized from a mRNA template
• Translation machinery:
  • Ribosomes: read mRNA, assemble amino acids
  • tRNA (transfer RNA): brings amino acids to ribosomes
  • Aminoacyl-tRNA synthetases: link amino acids to tRNA
• Steps:
  1. Initiation: ribosome binds to mRNA, initiator tRNA
  2. Elongation: amino acids are added to polypeptide chain
  3. Termination: protein synthesis stops, polypeptide is released
• Post-translational modifications: proteins may undergo folding, modification, targeting

Molecular Evolution

• Study of evolutionary processes at the molecular level
• Key concepts:
  • Neutral theory: most mutations are neutral, not affecting fitness
  • Molecular clock: rate of molecular change is constant over time
  • Phylogenetic analysis: reconstructing evolutionary relationships
• Types of molecular evolution:
  • Orthologs: genes with same function, different species
  • Paralogs: genes with same origin, different function
  • Xenologs: genes introduced from another species

Genomics

• Study of structure, function, and evolution of genomes
• Key concepts:
  • Genome: complete set of genetic information
  • Proteome: complete set of proteins encoded by a genome
  • Systems biology: study of biological systems as a whole
• High-throughput sequencing technologies:
  • Sanger sequencing: dideoxy chain termination method
  • Next-generation sequencing (NGS): parallel sequencing of millions of fragments
• Applications:
  • Personalized medicine: tailoring treatment to individual genomes
  • Synthetic biology: designing new biological systems

DNA Replication

• DNA replication occurs before cell division to create an exact copy of the cell's DNA
• The process is semi-conservative, resulting in two new DNA molecules, each containing one old strand (template) and one new strand
• Initiation involves unwinding of DNA and binding of replication fork
• Helicase unwinds DNA, and topoisomerase relieves tension during unwinding
• Primase adds RNA primers to template strands during binding
• DNA polymerase adds nucleotides to primers during elongation
• DNA polymerase checks for errors during proofreading
• DNA ligase seals gaps between nucleotides during ligation

Gene Expression

• Gene expression is the process of synthesizing a functional product from DNA information
• The Central Dogma outlines the flow of information: DNA → RNA → Protein
• Transcription is initiated when RNA polymerase binds to the promoter region
• RNA polymerase adds nucleotides to mRNA during elongation
• Transcription stops, and mRNA is released during termination
• Translation is initiated when a ribosome binds to mRNA
• Amino acids are added to the polypeptide chain during elongation
• Protein synthesis stops, and the polypeptide is released during termination

Protein Synthesis

• Protein synthesis is the process of synthesizing a polypeptide chain from a mRNA template
• Ribosomes read mRNA and assemble amino acids during translation
• tRNA brings amino acids to ribosomes during translation
• Aminoacyl-tRNA synthetases link amino acids to tRNA
• Initiation involves the binding of ribosome to mRNA and initiator tRNA
• Amino acids are added to the polypeptide chain during elongation
• Protein synthesis stops, and the polypeptide is released during termination
• Post-translational modifications include folding, modification, and targeting

Molecular Evolution

• Molecular evolution is the study of evolutionary processes at the molecular level
• The neutral theory states that most mutations are neutral and do not affect fitness
• The molecular clock concept suggests that the rate of molecular change is constant over time
• Phylogenetic analysis involves reconstructing evolutionary relationships
• Orthologs are genes with the same function in different species
• Paralogs are genes with the same origin but different functions
• Xenologs are genes introduced from another species

Genomics

• Genomics is the study of the structure, function, and evolution of genomes
• A genome is the complete set of genetic information in an organism
• A proteome is the complete set of proteins encoded by a genome
• Systems biology involves the study of biological systems as a whole
• Sanger sequencing uses the dideoxy chain termination method
• Next-generation sequencing (NGS) involves parallel sequencing of millions of fragments
• Personalized medicine involves tailoring treatment to individual genomes
• Synthetic biology involves designing new biological systems