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DNA Replication and Chromosomes (Basic Terminology (Ori (Origin of…
DNA Replication and Chromosomes
Basic Terminology
Ori (Origin of replication)
This is the place at which the two strands of DNA have separated
Semi-conservative model
This model states that when DNA is replicated, half of the DNA is 'old DNA' and results from the pre-existing strand, whilst half is 'new DNA' and has been pre-coded for by RNA primase.
This forms two identical daughter strands
Replication fork
This is the opening created between the two strands of DNA in preparation for the process of DNA replication. This strand is separated by DNA helicase
Nucleotide
The combination of a base (A, C, T, or G), a sugar, and a 3 phosphate molecules. When a nucleotide is added to a phosphate, a phosphodiester bond is formed
Homologous Chromosome
A pair of two chromosomes
P Arm
The short (top) arm of the chromosome
Q Arm
The long (bottom) arm of the chromosome
Enzymes
DNA Helicase
This is the enzyme that allows for the separation of the DNA strand (unwinding) in local points
DNA Gyrase
The enzyme that is involved in making sure that as the DNA is unravelled that it does not tangle.
This is done through cutting the DNA into smaller sections
Single-stranded binding proteins
Proteins
that keep the two DNA strands separate
RNA Primase
RNA Primase is the enzyme that allows for the template for the new strand to be set out with DNA bases. On the leading strand, RNA Primase is being constantly followed by DNA Polymerase III whilst on the lagging strand it makes certain parts at a time and DNA Polymerase III then copies this with DNA bases
DNA Polymerase III
This enzyme is what attaches the DNA nucleotides to the strand is what actually allows for the process of replication to be completed in terms of the placement of the bases.
This enzyme adds complementary nucleotides, proofreads the DNA, and repairs it. It travels from the 5' to 3' end
DNA Ligase
This enzyme is responsible for finally sealing the sequence that has been made by the DNA Polymerase III enzyme
and other breaks in the sugar phosphate backbone
Process
Mistakes
The process of checking for mistakes is called the 3'-5' exonuclease activity
Leading strand
The old fragment of DNA where replication is continuous towards the replication fork
Lagging strand
This strand has a discontinuous nature as it is in a 5'-3' nature. Therefore the chain is replicated in Okazaki fragments
Chromosome Modulation
Karyotype
The typing out of a nucleus (contains all of the chromosome pairs from 1 to 22 and including the 23rd haploid chromosome)
Nucleosome
A package of
8
histone proteins
Classes of histones
H1, H2A, H2B, H3, and H4
Solenoid
A looped structure found by the packing together of DNA