CH. 7 & 8 Prokaryotic Genomes & Gene Expression Flashcards
How do you define the genome, transcriptome, and proteome of a prokaryote?
Genome: the totality of DNA in a cell
Transcriptome: total transcripts present at a given time
Proteome: all the types and numbers of proteins expressed at a given time
How are genes organized in bacteria, specifically what is: (a) an operon; (b) structural and control genes; (c) monocistronic & polycistronic; and (d) a regulon?
Operon: region of DNA strand that contains promoter + operator + structural genes
Structural & Control Genes: genes that code for proteins in the body needed for structure or function
Monocistronic Gene: Genes that code for one protein
Polycistronic Gene: Genes that code for multiple proteins
Regulon: a group of genes or operons regulated by a single regulatory mechanism
What are plasmids? What are some of their features?
Plasmids are small, extra-chromosomal circular DNA segments
Features:
-2-25 kbp in size
-Autonomous
-Possess an ori
-Some can integrate into chromosomes and are transferable
How do low copy number plasmids and high copy number plasmids affect the latter?
Plasmid copy number determines the gene dosage accessible for expression and many plasmids lead generally to high productivity. High copy numbers are more likely to pass on to the next generations, and low copy numbers have par proteins separate plasmids to opposite poles
How are plasmids are maintained?
They are maintained by selective pressure. Plasmids will be lost if selective pressure are not maintained
What is rolling circle replication?
A process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA. It is the process by which one strand of DNA is spooled off into another cell during conjugation. The two separated strands get new complementary strands added to them, leading to two copies of the DNA
What are the process of transcription & translation and the end result for each process?
Transcription: DNA to mRNA using RNA polymerase and mRNA
Translation: mRNA to protein using transfer RNA’s and ribosomal RNA’s
What are the structural features of bacterial RNA polymerase and what are their functions in transcription?
Core Polymerase: synthesizes mRNA’ has 4 subunits, 2 alpha subunits, 1B, and 1B’
Sigma factor: promoter recognition, guides RNA polymerase to the promoter, then unbinds from core polymerase to initiate transcription
RNA polymerase also known as “holoenzyme”
What are ‐35 & ‐10 sequences, i.e., what is their significance? What component of RNA polymerase interacts with these sequences?
-35 & -10 sequences are the positions of DNA strands that the sigma factor binds to. They are known as consensus sequences (conserved sequences)
70-sigma factors of the RNA polymerase interact with these sequences which are common for most bacterial genes
What is the function of the Shine‐Delgarno sequence? Where is it found?
Binds to 16S ribosomal RNA of small (30S) ribosomal subunit; ribosome binding followed by a translation of transcript to form polypeptide
It is found on the ribosome binding site (near start codon)
What is meant by vertical gene transmission and horizontal gene transmission? What are examples of how each of these processes occurs in prokaryotic cells?
Vertical Gene Transfer: when genes are transferred down generations (ex. from parent to offspring as a result of sexual or asexual reproduction)
Horizontal Gene Transfer: when genes are transferred across from one individual to another in the same generation (ex. transformation, conjugation, etc.)
What is the difference between core and flexible gene pools?
Core gene pool: Genes common to all members of a species (informational genes)
Flexible gene pool: Genes present in only a subset of members of a predefined group (vary among members)
What are genomic islands? What are the different types?
Genomic Islands: transferred genetic elements containing a large number of genes of similar function
-Pathogenicity Islands: virulence genes antibiotic resistance genes
-Symbiosis Islands: bacteria-host interactions
-Fitness Islands: catabolic pathway
