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replicates the DNA of the organism. A duplicate strand of DNA is
Transcription is what and creates what? (what type of RNA?)
- DNA directed RNA synthesis, template strand is
- transcribed, transcription gives you 3 kinds of RNA: t, m and r.
Translation what is it and what does it do?
- genetic info in the form of
- mRNA is decoded into an amino acid chain.
Describe the structure of DNA
- A,G,C,T has a deoxy ribose sugar, missing its hydroxyl group at
- carbon 2. 5 carbon sugar ring.
Describe structure of RNA
- Has two hydroxyl groups. 5
- carbon sugar ring
Compare and contrast the organization of DNA in the chromosomes of:
Bacteria, Archaea, and Eukaryotes
- Bacteria has circular double helix or twisted supercoiled DNA,
- complexed with basic proteins,
ArchaeaCircular double helix, twisted into supercoiled DNA, contains histone and forms nucleosomes., and Eukaryotes. Associated with histones to form nucleosomes. Double stranded linear.
Describe Bidirectional replication
you synthesize in both directions along the DNA, and you get a replication fork.
- E.coli do this, observed
- during plasmid replication. One strand is nicked and the free 3’ hydroxyl end
- is extended by replication enzymes. The 3’ end grows while the 5’ end is
- displaced, like an apple peel.
Characterize the function of DNA polymerase
catalyze DNA synthesis, in the 5’ to 3’ direction (REPLICATION)
NEEDS: Template, primer, dNTPs
DNA poly 3 plays the major role in replication
proteins that bind to DnaA boxes within the origin of replication and use ATP to break H-bonds between DNA strands
- separate and unwind DNA
- strands, they use ATP to unwind short stretches of helix ahead of the fork.
- keep the strands apart and
- stop them from binding together.
proteins that relieve tension generated by the rapid unwinding of the double helix.
an enzyme that forms a short RNA sequence that is complementary to the DNA strand, allowing the DNApoly 3 to jump on.
Events at the replication fork
- 1. 40 DnaA proteins bind to OriC and hydrolyze ATP, separating the DNA strand
- 2. Helicase unwind the helix using topoisomerase like DNA gyrase.SSBs hop on
- 3. Primase synthesizes RNA primers. DNA poly III hops on and makes both leading and lagging strand.
- 4. Lagging strands form Okazaki fragments. DNA poly I removes RNA primer with 5' to 3' exonuclease activity.
- 5.Fragments are joined together by DNA Ligase
Synthesis of the lagging strand: who does it?
made discontinuously with okazaki fragments by DNA poly III
Proofreading-who does it? what end of the DNA?
Carried out by DNA poly III, removes mismatched base from the 3' end by exonuclease activity (not 100% efficient)
Termination of replication: who is involved and what happens
replisome reaches the termination site (on DNA) and ends replication. Catenanes form when 2 circular chromosomes do not separate. Topoisomerases temporarily break DNA molecules so strands can separate.
tRNA genes-describe the organization and structure. What structures does it have?
- can code for more than a single tRNA molecule or type of tRNA,
- spacers separate coding region and are removed after transcription.
Ribozymes: special ribonuclases that remove spacers.
- CONTAINS: promoter, leader,
- coding spacer, and trailer regions which are removed during maturation
rRNA genes- describe the organization and structure. What structures does it have in it?
Have a promoter, leader, terminator, coding spacer, and trailer region. Spacer and trailer regions may encode tRNA molecules