Lecture_Microbial_Genetics_I

Microbial Genetics Overview

• Part I

• Focus on the fundamental concepts of genetics and molecular biology relative to microorganisms.

The Code for Life

• Genome: The complete set of genetic material in an organism.

• Gene: A segment of DNA that contains the instructions needed to produce a gene product, typically a protein.

• Gene Product: The biochemical material resulting from the expression of a gene, which can be either RNA or protein.

• Flow of Genetic Information:

  • From DNA to RNA to Protein

  • First, DNA is transcribed into mRNA, and then mRNA is translated into a protein.

Flow of Genetic Information

• Within cells:

  • DNA Replication: The process of copying DNA before cell division.

  • Transcription: The synthesis of mRNA from a DNA template.

  • Translation: The synthesis of proteins using mRNA as a template.

• Between generations:

  • Daughter cells inherit the genetic information through the processes listed above.

Structure & Function of Genetic Material

• DNA Structure: Two strands twisted into a helix.

• Nucleotide Basics:

  • Components of a nucleotide:

    • Five carbon sugar (deoxyribose)

    • Phosphate group

    • Nitrogenous base (adenine, guanine, thymine, cytosine)

• Formation of the Sugar-Phosphate Backbone:

  • Nucleotides link through covalent bonds between 5' carbon and 3' carbon.

Nucleotide Structure

• Purines:

  • Adenine (A)

  • Guanine (G)

• Pyrimidines:

  • Cytosine (C)

  • Thymine (T)

• Base Pairing Rules:

  • A pairs with T

  • G pairs with C

DNA Replication

• Purpose: To produce identical copies of the DNA.

• Products: Two identical DNA molecules.

• Steps of DNA Replication:

  1. Unwinding of double helix by enzymes.

  2. Stabilizing unwound parental DNA.

  3. Leading strand synthesis by DNA polymerase (continuous).

  4. Lagging strand synthesis, involves RNA primer, Okazaki fragments, & DNA ligase joins fragments.

  5. DNA replication is semiconservative (each new DNA contains one old strand and one new strand).

Gene Expression

• Definition: The process by which a gene's information is used to synthesize its corresponding protein.

• Stages of Gene Expression:

  • Transcription: DNA is transcribed into mRNA.

  • Translation: mRNA is translated into a protein.

• Regulation: Gene expression occurs only as needed (regulatory mechanisms control the timing and amount of protein produced).

RNA Structure

• Function: Essential for protein synthesis.

• Structure: Single-stranded molecule.

• Components:

  • Bases: Adenine (A), Uracil (U), Guanine (G), Cytosine (C)

  • Sugar: Ribose

  • Phosphate groups.

Types of RNA

• mRNA: Carries instructions from DNA to ribosomes for protein synthesis.

• tRNA: Transfers amino acids during protein synthesis.

• rRNA: A structural component of ribosomes.

Transcription - Process

• Stages of Transcription:

  1. Initiation: RNA polymerase binds to promoter region of DNA, unwinding the DNA strand.

  2. Elongation: RNA polymerase synthesizes RNA complementary to the DNA template.

  3. Termination: RNA polymerase reaches a terminator sequence and disengages, releasing the synthesized RNA.

Translation - Process

• Definition: Synthesis of proteins from mRNA templates.

• Stages of Translation:

  1. Initiation: Ribosome assembles around the mRNA.

  2. Elongation: tRNA brings amino acids to ribosome and polypeptide chain elongates.

  3. Termination: Ribosome reaches a stop codon, releasing the completed protein.

• Simultaneity: In prokaryotes, transcription and translation can occur simultaneously.

The Genetic Code

• Codon: A sequence of three nucleotides that corresponds to an amino acid or stop signal during protein synthesis.

• Degeneracy: The genetic code is degenerate; multiple codons can code for the same amino acid.

Conclusion

• Understanding microbial genetics is essential to comprehend how microorganisms replicate, express genes, and produce proteins, which influence their function and behavior.