hl ib biology- d.1.1 dna replication

dna replication

dna replication

the production of new strands of dna, rewuired for reproduction, growth and tissue replacment

semi conservative nature of dna

when dna is replicated, the 2 strands of the double helix must seperate, both strands r used as templates, new strands are formed by adding nucleotides one by one and linking them together, dna is semi conservitive bc there are 2 dna molecules, compsed of an og template strand and a new synthesized strand

role of helicase

ring shaped protein that seperates the 2 strands of dna by breaking hydrogen bonds

role of dna polymerase

assembles new strands of dna using the 2 og strands at templates, dna polymerase brinds nucletides into the position whith hydrogen bonds, links the nucletide to the end f=of the new strand

polymerase chain reaction (PRC)

an automated method of dna replication, mixtures of dna sequences r put inot the PCR machine

applications of polymerase chain reaction

can be used for covid + paternity testing

pros and cons of polymerase chain reaction

pros- sensitve+ specific

cons- expensive, slow

dna profiling for paternity testing

this technique of dna profiling distinguishes individuals using bade sequences known as short tandem repeats

a sample of sna is obtained, selective tandem repeats r copied by PCR, dna is prodcued by PCR

how nucleotides r linked together

nucleotides r linked to form strands of dna+rna with covalent bonds between the sugar of one nucleotide and the phosphate of the next

diferences in leading strand and lagging strand

dna strands r anti-paralell, in a 5’ to 3’ direction

on one strand, dna polymerase adds nucleotides towards the replication fork, on the other strand dna polymerase adds nucleotides moving away from the replication fork

functions of dna primase

dna primase is a type of rna polymerase

it assembles a chain of ab 10 rna nucleotides to provide a site where dna polymerase III can bind and stard adding nucleotides to the 3’ of a dna strand

dna polymeras III

the principal polymerase in dna replication

it binds to the template strand on the 3’ end of the rna primer and assembles a chain of dna nucleotides and it also proofreads each nucleotide

dna polymerase I

binds to an okazaki fragment on a lagging strand

removes rna nucleotides and replaces them w dna nucleotides

dna ligase

connects the gaps in the chain of nucleotides left by dna polymerase

dna proofreading

errors are corrected, preventing mutations

proofreading happens durinig replication immidetily after a wrong nucleotide has been place

done by the dna polymerase III