3-1: Microbial Genome Flashcards
What is the first step in cell division
DNA replication
What part of mRNA is converted into proteins
Open reading frames
Nucleotides are comprised of what three components?
Nucleobase (nitrogenous base), deoxyribose, phosphate at 5’
What is the difference btw nucleoside and nucleotide?
Nucleosides lack P
How are nucleotides connected
Phosphodiester bonds btw 5’ P and 3’ OH
Why do C/G base pair stronger than A/T?
3 hydrogen bonds
Differences between RNA and DNA?
RNA = 2’ OH group on ribose sugar (less chemically stable), thymine replaced by uracil, single stranded
How are prokaryotic chromosomes structured
Circular with extensive supercoiling and additional structuring layered on top
What is the nucleoid
Region of cell containing chromosome (not membrane bound, but similar to the concept of the nucleus)
How many chromosomes do prokaryotes typically have?
One circular chromosome
What is an example of a bacterium with two chromosomes
Vibrio cholerae (one 3Mbp, one 1Mbp)
What is special about the streptomyces chromosome?
Linear!
Structure of eukaryotic chromosomes?
Multiple linear chromosomes, larger and less compact genomes compared to prokaryotes
What is special about eukaryotic microbial chromosomes?
Smaller and has more compact genes (fewer introns)
What are genes
Genetic material that encodes functional protein or RNA product
What is the typical prokaryote genome comprised of?
85-90% protein-coding genes, 1-2% noncoding RNA genes, 10% non-coding DNA (eg. regulatory sequences)
What direction do genes run?
Both directions (they can overlap too!)
How are genes organized
Functionally related clusters
Who has the smallest genome size?
Endosymbionts, parasites
What size genome does mycoplasma have?
0.5 Mb
What size genome do bacteria/archaea have?
Around 4.5 Mb
Why might some bacteria need really big genomes?
Those with complex life cycles
How are genome size and number of genes related in prokaryotes?
Genome size increase, so does number of genes
How does the genome composition change as genome size increases?
Higher proportion of genes responsible for regulation (eg. transcription, signal transduction)
What is the core genome
Genes present in all members (conserved genes)
What is the pan genome
All genes present in any member (includes rare genes)
What is synteny
Homologous genes arranged in same order in genomes of closely-related lineages
What is a genomic island vs islet
When unique genes of genome found in blocks
Island = large block
Islet = small block
What is the Salmonella Pathogenicity Island-1?
Encodes many genes needed for type III secretion system that allows Salmonella to enter host cells. Also encodes iron acquisition genes
What is a prophage
When a bacteriophage integrates into the bacterial genomes, become a part of it. Can be stable or transient
What is a cargo gene
Carried by prophage, have nothing to do with phage biology, provide the bacterial host with new genes
What is a plasmid
Circular DNA molecules replicated in the cytoplasm that encode “non-essential” genes (only required under certain conditions; e.g. antibiotic resistance genes)
What is the typically size and number of plasmids?
1kbp to 1Mp
Can vary from 1 to >100
