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Structure and Replication of DNA - Coggle Diagram
Structure and Replication of DNA
Replication
Requirements for DNA replication
Original DNA template
Free DNA nucleotides - to form new strands
DNA polymerase - adds nucleotides to a growing strand of DNA
Primers - a primer is a short strand of nucleotides that will bind to the 3' end of the template of DNA allowing DNA polymerase to add free DNA nucleotides
DNA replication is the process by which a cell makes an identical copy of its DNA
It occurs at the beginning of every cell division, so that when the cell divides, each daughter cell will inherit an identical copy of the DNA
Polymerase Chain Reaction
PCR is the amplification of DNA in vitro
PCR amplifies DNA using complementary primers for specific target DNA sequences
It turns a specific target sequence of DNA into millions of copies which can then be used for analysis
Can be used for
Provide DNA samples for criminal investigations
Settle paternity suits
Diagnose genetic disorders
Requirements
Thermal cycler
- equipment that varies the temperature of the reaction
Heat-tolerant polymerase
- adds nucleotides to the growing strand and is not denatured by the high temperatures used in the reaction
Primers
- primers are short complementary sequences of nucleotides needed to start DNA synthesis
Supply of nucleotides
- to synthesise the new strands of DNA
DNA
- original strand of DNA which needs to be amplified
Process
Primers added
- which are complementary to the target sequences at the two ends if the region to be amplified
Heated
(70-80) - tolerant DNA polymerase added
DNA cooled
(50-65) - to allow primers to bind to target DNA sequences
Repeated cycles of heating and cooling amplify the target region of DNA
DNA heated
(92-98) - to denature the DNA and separate the two strands
Bases
The bases are thymine, adenine, cytosine and guanine
The complementary base pairings are A-T and G-C
The order of bases controls the order in which amino acids are assembled to make a specific protein
A sequence of 3 bases is the code for a particular amino acid - known as a triplet
DNA Structure
It's structure is described as a double-stranded helix
A nucleotide consists of a phosphate, deoxyribose sugar and a base
Consists of nucleotides
Strong bonds form a sugar-phosphate backbone
The 5' end at the phosphate end
The 3' end at the deoxyribose end
The two strands of DNA are antiparallel, which means that one strand runs in a 5' to 3' direction and the other runs in the 3' to 5' direction
Genetic information is stored in the base sequence of DNA
The base sequence of DNA forms the genetic code
The genotype is determined by the sequence of bases
Stages
Stage 2
DNA polymerase adds the free DNA nucleotides to the 3' end of the primer
Leading strand
is synthesised
continuously
- DNA polymerase adds nucleotides to the deoxyribose ended strand in the 5' to 3' direction
Lagging strand
is synthesised in
fragments
- nucleotides can only be added in the 5' to 3' direction so the lagging strand is synthesised in fragments, then later sealed with
ligase
A primer is needed to start replication
Stage 3
The two new
strands twist to form a double helix
. Each is identical to the original strand
Stage 1
The DNA is unwound and unzipped
Helix structure is unwound
Weak hydrogen bonds break between bases, which are holding the strands together
This occurs at several locations on a DNA molecule