9.5 Genetic material Flashcards
What is polymorphism in mo
Polymorphism is ability of some microorganisms to alter their morphology, biological functions, or reproductive modes in response to environmental conditions. Pleomorphism is particularly prevalent in certain groups of bacteria, yeasts, rickettsias, and mycoplasmas, which can exhibit irregular and variant forms within the same species or strain
How long is bacterial chromosome
More then length of bacterium. DNA is supercoiled and packed with help of Nucleoid-associated proteins (NAPs)
What are NAPs influencing
They shape DNA structure and function. Aside from influencing their topology( by wrapping it) they constrain supercoiling and contribute to nucleoid formation. They regulate gene expression, participate in short-range interactions, impact processes like transcription, translation and transfer
Compare Archaeal chromosome and proteins with bacterial
Archaeal chromosome is circular and some species are polyploid( more than one copy of the chromosome per cell)
Associated proteins are different from the bacterial ones, though some have similar function. Some archaea have eukaryotic-like histones
What are characteristics of bacterial DNA replication
*semi-conservative
*bidirectional replication
*two replication forks
What does it semi-conservative replication mean
During replication, each DNA strand contains one original( parental) strand and one newly synthesized( daughter) strand. Parental strands serve as templates for the synthesis of complementary daughter strands
What do replication forks do
Unwind double-stranded DNA
Where does initiation of replication starts
At oriC( origin of replication)
Who starts replication
Initiator proteins. Origin recognition complex( ORC) binds to the origin marking it as a starting point
What do initiator proteins do
Break hydrogen bonds between the strands, forming replication bubble
Who binds to the template DNA in replication bubble
SSB: single stranded binding proteins
What happens in replication after SSB connect to the strands
Helicase and primase connect to replication forks and form primase
What does helicase do at replication fork
Unwinds DNA strands
What does primase do
Attaches RNA primers which allows DNA polymerase III to synthesize DNA on the leading strand in 5’ to 3’ direction
What does DNA Polymerase III do on the lagging strand?
As RNA primase leaves primers, DNA polymerase III makes Okazaki fragments and DNA polymerase I removes DNA primers on the lagging strand and replaces it with DNA
Who joins Okazaki fragments together
DNA ligase
What happens at the end of replication
Each strand of DNA will consist of 1 parental strand and 1 daughter strand
What is replisome
The replisome is a complex molecular machine responsible for DNA replication.
What holds 2 DNA polymerase assembles and helicase together
Tau subunits
What does gyrase do
It’s ahead of replication fork and relieves the torsional stress that builds up. It does this by introducing negative supercoils in DNA, allowing helicase to function better
In what direction is synthesis done
In opposite directions
What is ter
Terminus of replication. When replication fork hit it and collide, it releases 2 chromosome copies. One set of Ter sites arrest DNA forks progressing in clockwise direction, a second set arrests forks in the counterclockwise directions
What binds to the Ter sites
Tus protein-a monomer. It inhibits replication fork progression by directly contacting DNA-B helicase, thus inhibiting DNA unwinding
What are plasmids
Extra-chromosomal elements with self-replicating ability. They are usually dsDNA with variable length. Pool of extrachromosomal DNA for horizontal gene transfer
Are plasmids essential
No, they also have simple genetic growth
What kind of plasmids do we have
-
Metabolic: confer some metabolic functions like degradation of toxins, use of compounds as a source of energy
2.Resistance(R):antibiotics, toxic metals
3.Virulence:production of bacteriocins, invasion of animal cell and tissues, toxins and capsule
4.Conjugation(plasmid F)
How can we differentiate plasmids based of their copy number
-Low copy number- usually 1-3 copies; they often contain genes that are toxic for the cell at higher concentrations
-High copy number-30-50
What does the ability to transfer plasmids to daughter cell depend on
Copy number:
Low copy number->high risk to lose the plasmid
Because of this there was evolution of segregation syste,s
What are ParC, ParR and ParM
ParC- specific sequence of the plasmid
ParR- protein that bids ParC and ParM
ParM- polymerising protein that produces filaments that allow equal partitioning
How can plasmids coexist in the same cell
They have to be compatible
If two of them are incompatible one of them will be lost during cell division
When are two plasmids incompatible
When they have same origin of replication. The smallest one replicates faster and will survive
They are also incompatible when they compete for the same replication factors( similar origins)
What usually happens to plasmids
They diffuse into the cytoplasm of bacterial cell
What’s transposition
Process by which a DNA sequence can repeatedly move from one location to another within the chromosome by insertion
What’s transposition similar to
Site-specific recombination
What are insertion sequences
Insertion sequences(IS)_sequencess of 700-2000 bp(base pairs) with inverted and repeated sequences at both ends(16-25bp).IS contains at least the transposase gene, which encodes the protein responsible for the site-specific recombination
What can IS transposition induce
Insertional mutagenesis
What are trasposons
Mobile genetic elements more complex that insertion sequences
They include other genes aside from transposase
What do tasposons carry
Resistance genes to antibiotic and toxins
What is difference between eukaryotes and prokaryotes when it comes to replication, transcription and translation
-Euk: Transcription and translation happen as separate moments while in prok they happen simultaneously
-In euk: transcription happens in nucleus, forming complementary mRNA from DNA . The way pre-mRNA matures before exiting nucleus is by addition of 5’cap and 3’poly-A tail.
-In euk there is splicing of introns( noncoding parts od DNA) and they are removed and only exons are left
