1.4 Central Dogma of Molecular Biology

The central dogma of molecular biology explains how genetic information flows from DNA to RNA to proteins. It's the foundation for understanding how our genes control our traits and bodily functions. This process involves DNA replication, transcription, and translation.

DNA replication ensures each cell has a copy of our genetic blueprint. Transcription creates RNA messages from DNA, while translation uses those messages to build proteins. These steps are crucial for passing on genetic info and making the molecules that keep our cells running.

The Central Dogma of Molecular Biology

Central dogma of molecular biology

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• Describes the flow of genetic information within a biological system
  • DNA serves as the blueprint stores genetic information in the form of nucleotide sequences (A, T, C, G)
  • RNA acts as a messenger carries genetic information from DNA to ribosomes for protein synthesis (mRNA, tRNA, rRNA)
  • Proteins are the functional molecules perform various cellular tasks (enzymes, structural proteins, signaling molecules)
• Key processes involved in the central dogma:
  • Replication: Copying DNA to create identical DNA molecules ensures genetic continuity
  • Transcription: Synthesizing RNA from a DNA template converts genetic information into a form that can be used for protein synthesis
  • Translation: Synthesizing proteins using the information carried by mRNA converts genetic information into functional molecules

DNA replication and genetic maintenance

• DNA replication is a semiconservative process occurs before cell division
  • Each strand of the double-stranded DNA molecule serves as a template for the synthesis of a new complementary strand
  • DNA polymerase enzymes catalyze the addition of nucleotides to the growing DNA strand (A pairs with T, G pairs with C)
  • The resulting two DNA molecules are identical to the original DNA molecule
• Importance of DNA replication in maintaining genetic information:
  • Ensures that each daughter cell receives an exact copy of the genetic material after cell division (mitosis, meiosis)
  • Preserves the genetic integrity of an organism across generations prevents accumulation of mutations
  • Allows for the transmission of genetic information from parent to offspring basis of heredity

Transcription and RNA in gene expression

• Transcription is the process of synthesizing RNA from a DNA template
  • RNA polymerase enzymes catalyze the synthesis of RNA by adding ribonucleotides to the growing RNA strand (A, U, C, G)
  • Transcription occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells
• Role of RNA in gene expression:
  • Messenger RNA (mRNA) carries the genetic information from DNA to ribosomes for protein synthesis
  • Transfer RNA (tRNA) molecules transport amino acids to the ribosome and help decode the genetic information carried by mRNA (anticodon-codon pairing)
  • Ribosomal RNA (rRNA) is a component of ribosomes and plays a role in the catalysis of protein synthesis

Translation for protein synthesis

• Translation is the process of synthesizing proteins using the information carried by mRNA
  • Ribosomes, which are composed of rRNA and proteins, are the sites of protein synthesis
  • mRNA is read in a 5' to 3' direction, with each codon (a sequence of three nucleotides) specifying a particular amino acid
  • tRNA molecules, carrying specific amino acids, base-pair with the codons on the mRNA (anticodon-codon pairing)
  • The ribosome catalyzes the formation of peptide bonds between the amino acids, creating a growing polypeptide chain
• Synthesis of proteins from mRNA:
  1. The genetic code determines the relationship between codons and amino acids
     • 61 codons specify 20 different amino acids, while 3 codons serve as stop signals (UAA, UAG, UGA)
  2. The polypeptide chain undergoes folding and post-translational modifications to form a functional protein (disulfide bonds, glycosylation, phosphorylation)
  3. Proteins perform various functions in the cell (catalyzing reactions, providing structural support, regulating gene expression)