DNA REPLICATION AND TRANSCRIPTION Flashcards
DNA replication direction
5’ (phosphodiester) to 3’ (hydroxyl group)
¿In which area of the DNA does the replication begin?
In the origin of replication (Adenine and thymine)
¿How many hydrogen bonds are in an Adenine and Thymine union?
Two hydrogen bonds
¿What is the function of the Single Stranded Biding Protein (SSBP)?
Prevents the parental strands from reconnecting and protects from enzymes (nucleases) that can break the phosphodiester bonds.
¿What is the function of the helicase?
Unwinds the DNA on both replication forks, it requieres a ton of ATP
¿How are supercoils formed?
In the process of unwinding, the DNA bunches up and ends up in the formation of supercoils
¿What is the function of the topoisomerase?
Relaxes the DNA supercoils
¿What is the structure of the topoisomerase and how does it work?
It has two arms; one cuts the DNA (nuclease) and the other arm re-stitches (ligase) after the unwinding of the supercoils.
¿What is the function of the Primase?
Makes RNA primers which allows the DNA polymerase type III to synthesize DNA.
¿In which direction does the Primase read the DNA strand?
It reads the DNA from 3’ (Hydroxyl group) to 5’ (phosphodiester)
¿In which direction does the primer synthesize?
It synthesizes the new strand adding the first nucleotides in the origin of replication form 5’ (phosphodiester) to 3´ (hydroxyl group)
¿What is the function of the DNA polymerase type III?
It synthesizes the brand-new strand of DNA
¿What does the DNA polymerase type III need in order to perform its function?
It needs the OH (hydroxyl group) from the RNA primers in order to continue to build nucleotides
¿From which direction does the DNA polymerase read?
3’ to 5´
¿From which direction does the DNA polymerase type III synthesize?
Synthesizes from 5’ to 3’
¿While the DNA polymerase type III is performing its function of proofreading, in which direction does it do it?
It reads from 3’ to 5’ (exonuclease activity)
¿What is the main function of DNA polymerase type I?
It removes the RNA primers and synthesizes 5’ to 3’ but it cannot fuse the ends to the original DNA.
¿What is the function of Ligase?
Fuse DNA ends together after the DNA polymerase type I has performed its function
¿What are exonucleases?
Enzymes that catalyze the removal of nucleotides via hydrolysis
¿What are Okazaki Fragments made of?
Are short DNA sequences with an RNA primer at the end 5’
¿What are Okazaki Fragments?
Okazaki Fragments are short segments of DNA that are synthesized on the lagging strand. These fragments are complementary to the lagging strand.
¿What are the main function of RNA polymerase?
- It binds to the DNA though the initiation process and it opens up the DNA
- Stabilizes the single stranded DNA
- Unwinds the DNA
- Reads the negative (anti parallel) strand from 3’ to 5’
- Synthesizes the RNA from 5’ to 3’
¿What type of RNA its used in the transciption process?
RNA polymerase type II
¿To what end does the cap binds to?
To the phosphate group (5’)
