DNA Replication Flashcards
What are the pairs of bases and how many H bonds do they have
AT - 2bonds
GC - 3bonds
What are the names of single ring bases
what are the names of double ring bases
single: pyrimidines. thymine, cytosine
double: purines. Adenine, guanine
what are the names of the proteins used in vito DNA repliaction in cells
Helicase
DNA polymerase 1 and 3
DNA ligase
RNA primase
toposomerisum
single strand binding proteins
what is the difference in function of
DNA polymerase 1 and 3
3: from RNA primers will move in the 5-3 direction adding complementary nucleotides, checks for errors, can move back and replace if any are noticed.
1: find DNA:RNA hybrydes and degreades rna component replaces with a corrosponsing DNA nucleotide
why are DNA ligase and RNA primer important
RNA primer: for DNA polymerase 3 to start adding corrosponding bases it requires a chemically acitve OH group at the 3c end to synthesise 5-3. (a 5 bonds to the avalible 3 OH.) RNA primer adds RNA nucleotide primers to points on the parent strand starting the leading strand and okazaki fragments.
DNA ligase: is important as when DNA polymerase 1 has degraded RNA bases and replaced, DNA ligase comes along and bonds adjacent nucleotides together forming phosophodiester bonds.
also connects repliation bubbles to one annother
why do we need topoisomerisum and what does ssbp stand for anf do?
topoisomerisum is used to release tention build up in DNA when it is unwound by helicase. breaks two parent stands appare and reforms them once it has been release,
sigle stranded binding proteins are used to bond to each strand of the DNA once they have been seperated to prevent them form reforming back into one sigle strand. they are also used to protect the strands from other present enzymes which may attemp to bind/damage the DNA structure
what is the name of the regon where replication happens and the name of the edge of thsi zone.
replication bubble
replication fork
what was chargaffs discovory
AT and GC pairs were in roughly the same ratios. but ht eoverall ratio of dna was not 1:1:1:1
why do DNA strands run anti parralel
as each DNA strand is developed from the 5-3 prime direction. the bases must point inwards to frm h-bonds between bases. so these bonds can form they must have the 5-3 doing down and 5-3 going up on the other strand
what are the properties of the watson and cricket model
double helix
anti parralel
bases pointing toward the center
h-bonds formed between bases
sugar phosphate backbone
why is replication semi conservative
1 parent strand and 1 daughter strand in each new DNA molecule which is form when dna is replicated. 1 parent is conserved 1 is new, semi conservative
why is DNA replication semi discontinuous
due to there being a leading strand and multipe lagging strands. which arent continuous
what is the name given to lagging strands in DNA replication
okazaki fragments
what are the two ways DNA errors can be fixed and how do they occour.
exonuclease: During dna construction, DNA polymerase 3 checks all added bases to their pairs. if an error is detected exonuclease shirts in the 3-5 direction removing and corecting the error.
endonuclease: after a DNA strand iof there is an error a whole segment of DNA must be removed. (we dont have a fine enough tool to make single nucleotide corrections.) this section is then remade by A DNA POLYMERASE (NOT 1 or 3!) joined by DNA ligase
why is it important to not leave errors in replicated DNA
all furture strands will have this error in them. the replicated strand from this will also have the wrong base pair attached leading to two diffrent DNA strands which are then replicated.
