12. Prokaryotic and eukaryotic genome organization. Types of DNA sequences. DNA-binding proteins. Regulation of gene expression in prokaryotes and eukaryotes.
Covers prokaryotic genome structure, including the circular chromosome, nucleoid, plasmids and histone-like DNA packaging, then the lac and tryptophan operons with their regulators, CAP and the lac repressor. Sporulation, germination and bacterial conjugation follow. The note goes on to DNA sequence classes, heterochromatin and euchromatin, the Barr body, DNA methylation with methyltransferases, histone tail modifications, eukaryotic promoter elements such as the TATA box, enhancers and silencers, DNA-binding motifs, and gene silencing. Several operon diagrams and a question-and-answer on methyltransferases are included.
Inside: 4 sections · 7 labelled pictures · 9 min
Topic 12 of 64 in the MU Sofia syllabus for Biology (Dental Medicine, Year 1). The free AceMed note covers it in 3 sections, about 1,333 words (9 min of reading).
In this note
Introduction
Operons
Sporulation and germnination
Introduction
Prokaryotic Genome:
Compact genome with minimal noncoding DNA, primarily in regulatory regions.
Bacterial Chromosome:
Single circular, double-stranded DNA molecule.
Nucleoid:
Cytoplasmic region occupied by a DNA-protein complex.
Plasmid:
Small circular DNA molecules replicated independently of the bacterial chromosome.
DNA Packaging:
DNA is packaged into histone-like proteins in bacteria.
Transcription Regulation in Prokaryotes:
Regulated by altering transcription rate primarily during initiation.
Involves protein and promoter interaction.
Binding Sites of Regulative Proteins:
Bind to major grooves of the DNA helix, with some proteins also utilizing the minor groove.
The initial DNA-protein interaction involves RNA polymerase (RNA pol) and the promoter.
Binding of Bacterial RNA Pol Sigma Subunit:
Bacterial RNA polymerase sigma (σ) subunit binds to the -35 sequence when the TTGACA sequence is recognized and bound by σ.
Subsequently, the core enzyme binds for elongation.
Subunits of RNA Pol and their Roles:
RNA polymerase has five subunits.
The σ subunit is necessary only for initiation.
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