d1.1 dna replication Flashcards
3 types of replication
- full conservative replication
- semi conservative replication
- dispersive replication
what is dna replication used for [3]
- reproduction
- growth
- tissue replacement in multicellular organisms
advantages of semi conservative dna replication
high degree of accuracy in copying base
sequences
what is one monomer of dna called
nucleotide
how are strands of polypeptides arranged
antiparallel
end of pentose
c5 prime end
bc shape of ribose
what bonds link carbon tgt + which ones
carbon bonds
c3 + c5
bond between srtands of polypeptide
h bond
y can the dna spiral
h bonds holding the antiparallel strands of polypeptides together
process of dna replication
- dna helicase
- unzips the double helix
- replication fork is formed - dna polymerase
- chases dna helicase + elongate the strands
- new daughter strands formed
= end up with 2 new double helixes
limitation of dna polymerase
can only travel form 5’ to 3’ end
- dna polymerase has to leap or else a gap will form
name of 2 strands during dna replication
- leading strand
- lagging strand
relationship of the 2 strands during dna replication
complementary
what is around when the dna replication occurs
free dna nucleotides
how to speed up the replication process in eukaryotic cells
multiple replication forks to speed up the replication
purpose of polymerase chain reaction
amplify dna sample
when is polymerase chain reaction needed
if you only have a small samples of DNA but you want to have a lot in order to use them for tests
real life application for polymerase chain reaction [3]
- test for viruses’ dna
- amplify insulin gene and insert in bacteria’s plasmids (recombination)
- dna fingerprinting/profiling
why is Taq polymerase used in polymerase chain reaction
heat resistant
- opt temp is 72c
- wont denature at 90c
why is dna helicase not needed in polymerase chain reaction
the double helix will just separate under heat (h bonds are very weak)
before polymerase chain reaction
- know the target sequence
- design primers that are complementary to the target sequence
primers definition
short pieces of dna that will attach on either end of the target
what is needed during polymerase chain reaction [4]
- many copies of the 2 primers
- dna polymerase
- nucleotides
- water + salt
purpose of dna polymerase during polymerase chain reaction
copies dna
purpose of nucleotides during polymerase chain reaction
act as dna building blocks
purpose of water + salt during polymerase chain reaction
mimic conditions inside the cell
how is the process of polymerase chain reaction regulated
through repeated cycles of temperature changes
temperature cycles of polymerase chain reaction (brief)
- 95c
- disrupts the complementary base pairing - 50c
- complementary strands re-join
- primers lock onto their complementary sequences before the longer strand can come back tgt - 72c
- activates dna polymerase
- attaches at the ends of the paired primers + extends them
95c detailed description
- close to boiling- disrupts the complementary base pairing
- 2 dna strand come apart
50c detailed description
- complementary strands re-join
- primers are present in much greater numbers- lock onto their complementary sequences before the longer strand can come back tgt
72c detailed description
- activates Taq polymerase
- attaches at the ends of the paired primers + extends them
- moves along the single-stranded dna, adding complementary nucleotides - goes until it falls off, reaches the end of the strand or temp change
cycle 2 of pcr
- 95c
- dna strands separate - 50c
- primers find their complementary sequences
- bind not only to the original target dna + products from cycle 1 - 72c
- polymerase extends to primers, adding complementary nucleotides as it goes
cycle 3 of pcr
- desired products appear
- shorter copies of just the target sequence
what does the primer consist of
a few nucleotides
(short complementary sequence of dna/rna)
what needs to occur before a dna polymerase bind to the parent strand
primer bind to the parent strand first
problem with primers
con only bind at 54c
what does primer sequence determine
where the copying starts and end
purpose of restriction endonuclease
cut at the ends of the tandem repeats to create fragments of dna of different lengths
2 types of cutting sites
- sticky end
- blunt end
y is restriction enzyme used to compare dna
for fair comparison since the cuts occur at the same places
gel electrophoresis pro
much faster
process of gel electrophoresis
- use pcr to amplify dna samples collected
- use 1 restriction endonuclease to cut the dna specifically into fragment
- fluorescent marker to tag a specific dna sequence
- match the fluorescent bands for results
y will the dna move during gel electrophoresis
dna is negatively charged. the shorter fragments will travel further than the longer fragments, as they are attracted by the positive side of the gel
y r the dna different lengths during gel electrophoresis
short ones travel quicker
process of dna replication
- helicase unzips and unwinds the dna
- the replication fork forms
- single strand binding porteins keep the dna from binding together again
- dna primase adds rna primers to the template strands
- dna polymerase III binds at the primers and begins to synthesise the new strands
- dna polymerase I removes rna primers and replaces them with dna necleotides
- dna ligase connects the Okazaki fragments
function of gyrase
relives the tension in the dna as it is unwound
function of dna helicase
unwinds and unzips the dna by breaking hydrogen bonds between bases
function of dna polymerase III
builds the new strands of DNA using the original strands as templates + proofreading function helps to prevent DNA replication errors
function of dna primase
places rna primers on the template strands
function of dna polymerase I
replaces rna primers with dna nucleotides
function of dna ligase
connects the okazaki fragments by forming phosphodiester bonds
function of single strand binding proteins
keep the two strands of dna separated and stable during replication
what would happen if the dna polymerase I didnt do its job
rna primers would remain in the dna molecule
what would happen if dna polymerase III didnt to its job
if mutation occurs, then it would trigger apoptosis
how translation depends on complementary base pairing
- translation converts a sequence of mRNA nucleotides/codons to a sequence of amino acids/polypeptide/protein
- triplets of nucleotides/bases on «activated» tRNAs pair with complementary «triplets of» nucleotides/bases on mRNA / vice versa
- base pairing occurs when adenine/A pairs with uracil/U and guanine/G pairs with cytosine/C
- specific amino acids are attached to specific of tRNA
e. mRNA has codons AND tRNA has anticodons
function of Taq DNA polymerase
- forms new double-stranded DNA by adding complementary bases/nucleotides
- primers binds to targeted DNA sequences at a lower temperature
why use Taq DNA polymerase
can withstand high temperatures without denaturing
process of pcr w temp
- denaturation (95c)
- annealing (54c)
- elongation (72c)
sense strand nucleotides
same as mRNA but T instead of U
r sense strands transcribed
non-transcribed
what are the non-coding regions in DNA used as
telomeres and coding for production of tRNA
which cell component synthesises actin and myosin
free ribosomes
which processes do nucleosomes play a role in eukaryotes [2]
- transcription regulation
- dna supercoiling
functions of dna
- code amino acid sequence of polypeptides
- regulation of gene expression
- introns (regulation too)
- telomeres (form caps at chromosome ends)
- coding for tRNA/rRNA
- allow genes to be passed to offspring
