Bacterial genome Flashcards
What is a gene?
Region of DNA (RNA in some viruses) encoding a discrete hereditary characteristic
What do genes include?
Coding sequence
Non-coding (regulatory) sequence
Introns (eukaryotes)
What does the bacterial genome determine?
Phenotype (how bacterium looks and functions)
How are genes organized?
Organized into chromosomes and extra-chromosomal genetic elements (plasmids)
True or false: Bacteria is diploid
Bacteria is haploid
How are bacterial chromosomes kept in nucleoid?
Highly compacted
Kept in nucleoid thanks to nucleoid associated proteins (HU protein)
What is the size of chromosomes in bacteria?
0.6 Mb (base pairs) to 10 Mb
What is the size of plasmids in bacteria?
1 kb > 1 Mb
True or false: Bacterial chromosomes and plasmids are solely circular
False: Can be circular and linear
What is negative supercoiling?
DNA double helix is underwound - strands separate more easily
What is positive supercoilingg?
DNA double helix is overwound - strands harder to separate
How is supercoiling regulated?
Regulated in cell by topoisomerase enzymes like DNA gyrase
Why is relaxing positive supercoiling important?
Important for replication and transcription
How is the replicating prokaryotic genome process?
DNA replication proceeds in both directions until replication complexes meet
What is the difference between chromosomes and plasmids?
Chromosomes -> carry essential genes
Plasmids -> carry non-essential genes
What are transposons?
Knock out genes and stop them from working
Capable of moving from one site to another
What is the copy and paste transposition?
Copy of itself (replicative)
What are HGTs?
Transposition from chromosome to plasmid
What is the cut and paste transposition?
Cuts out and moves elsewhere (non-replicative)
What are bacteriophages?
Virus that infects only bacteria
Protein capsid surrounding nucleic acid genome
What are the two types of bacteriophages?
Lytic or lysogenic
What is a lytic phage?
Replicates then lyses (destroys) their host
What is lysogenic phage?
Insert into genome and passively replicated with chromosomes
What are prophages?
Lysogenic phage inserted into genome that carry important genes
Are prophages important for HGTs?
Yes, are important vehicles for HGT
