Week 5

Functional Differences between DNA and RNA:

• Structure:

  • DNA: Double-stranded helix

  • RNA: Single-stranded

• Sugar:

  • DNA: Deoxyribose

  • RNA: Ribose

• Nitrogenous Bases:

  • DNA: Adenine (A), Guanine (G), Cytosine (C), Thymine (T)

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

• Function:

  • DNA: Stores genetic information

  • RNA: Involved in protein synthesis and gene regulation.

Process of DNA Replication:

• Initiation: Begins at specific sites called origins of replication; helicase unwinds the DNA double helix.

• Elongation: DNA Polymerase III adds new nucleotides complementary to the template strand.

• Leading and Lagging Strands: Leading strand synthesized continuously; lagging strand synthesized in segments (Okazaki fragments).

• Termination: Replication concludes when replication forks meet; results in two identical DNA molecules.

How Bacteria Replicate Their Genome:

• Bacteria utilize binary fission, whereby the DNA is replicated, and the cell divides.

• The circular chromosome is unwound, and replication occurs bidirectionally from the origin of replication.

• The process is relatively fast, allowing bacteria to replicate their genomes within approximately 20-30 minutes under optimal conditions.

Process of Transcription:

• Initiation: RNA Polymerase binds to the promoter region of the gene.

• Elongation: RNA strand is synthesized from the DNA template, adding complementary RNA nucleotides.

• Termination: RNA polymerase reaches a termination signal, releasing the newly formed RNA strand.

• The RNA strand undergoes processes like 5' capping and polyadenylation.

What Makes Up a Gene:

• A gene consists of a specific sequence of DNA that contains coding sequences (exons) and non-coding sequences (introns).

• Genes include regulatory sequences (promoters) that control the expression and timing of their transcription.

Process of Translation:

• Initiation: Ribosome assembles around the mRNA, and the start codon (AUG) is recognized by tRNA carrying Methionine.

• Elongation: Ribosome moves along the mRNA, and tRNAs bring corresponding amino acids, forming a polypeptide chain.

• Termination: Ribosome encounters a stop codon (UAA, UAG, UGA), resulting in the release of the new protein.

Definitions:

• Shine-Dalgarno sequence: A ribosomal binding site in bacterial mRNA recognized by the ribosome for the initiation of translation.

• Bacterial operon: A cluster of genes under the control of a single promoter that are transcribed together; functions in coordinated gene regulation.

• Plasmid: A small, circular DNA molecule that replicates independently of chromosomal DNA; often carries genes beneficial for survival.

• Transposon: Mobile genetic elements that can move within and between genomes, potentially disrupting genes and contributing to genetic diversity.

Functioning of a Bacterial Operon in Metabolic Processes:

• Operons regulate gene expression according to environmental conditions, ensuring efficient metabolic activity. For instance, the Lac Operon is activated in the presence of lactose, allowing the metabolism of this sugar.

Differences in Replication Between Bacteria, Eukaryotes, and Archaea:

• Bacteria: Circular DNA, replication occurs bidirectionally, often within the cytoplasm, utilizing fewer origins of replication.

• Eukaryotes: Linear DNA, requires multiple origins for replication, takes place in the nucleus, involves more complex replication machinery and longer time frames.

• Archaea: Similar to bacteria in having circular DNA but shares some mechanisms with eukaryotes, reflecting evolutionary links.

Causes of Genetic Mutations:

• Spontaneous mutations can occur during DNA replication errors.

• Induced mutations result from environmental factors such as UV radiation or chemical mutagens.

Repair of Genetic Mutations:

• Cells have repair mechanisms such as nucleotide excision repair and mismatch repair that can recognize and correct erroneous base pairing and structural damages.

Effects of Genetic Mutations:

• DNA Sequence: Mutations can alter the nucleotide sequence, potentially leading to changes in gene function.

• Protein Sequence: Mutations may result in altered amino acid sequences, leading to dysfunctional proteins or variations in protein function.

Explanation of Processes:

• Transformation: Uptake of naked DNA from the environment into a bacterial cell, leading to genetic changes.

• Conjugation: Direct transfer of genetic material between bacteria through a pilus, often involving a plasmid transfer.

• Transduction: Transfer of DNA from one bacterium to another via a bacteriophage, which can either be generalized or specialized.