Please enable JavaScript.

Coggle requires JavaScript to display documents.

DNA Structure, A332 P13 Mind Map Name: Nur Umairah Asbullah Student ID…

- - - - Where hairpin loop became a signal to terminate the transcription
    - - Example
        Hairpin formation during replication
        
        Where hairpin can fold on single stranded DNA (ssDNA)
        
        Formed by discontinuous replication of lagging strand
        
        OR
        Formed on ssDNA gaps remaining after lesion bypass
        
        OR
        Formed on ssDNA with lesion as part of the loop
        
        Due to inefficiency of repair mechanism to repair the defect on ssDNA
        
        Hairpin loop will allow the RNA polymerase to "jump over" so to replicate the rest of the strands & not blocked by lesion
  - - - Example
        If DNA strand has AACT followed by several bases including AGTT, the strand can form hairpin loop by folding back on itself
  - - - Able to modify the access of proteins to DNA
      - Directly recognized by proteins as such that these proteins bind to DNA if there is any presence of cruciform
      - Structure
        
        Appears as several hairpin loops
        
        Crucifix-like structure composed of DNA
        
        Cruciform DNA Eukaryotic cells
        contain DNA-binding protein that can specifically recognize cruciform DNA
        
        Cruciform DNA structure is formed by incomplete exchange of the strands between the double-stranded helices
      - Example
        
        DNA-binding Protein is Crp1p
        
        found in the yeast Saccharomyces cerevisiae
      - Interactions with ubiquitous protein plays a crucial role for the conformation of cruciform DNA
      - consists of 1 double stranded DNA resulting in 2 DNA hairpins
- - - - H bonds to hold the multi-strand structure of Holliday junction together
        
        To form platform for recombination & DNA repair
    - - To exchange segments of genetic information
  - - - 1 strand from one duplex invades other duplex leading to formation of D-loop
        
        Cleavage of D-loop & subsequent ligation results in Holliday junction, linking 2 duplexes
        
        Isomerization of strand
        
        Flipping of structure will occur
        
        Cleavage of strand to alter the 4 strands into 2 separate strands DNA molecule
        
        Depending on the horizontal / vertical cleavage, it will either give off Recombinant DNA or not
  - - - Example
        Double Strand Break (DSB)
        
        Can be repaired via formation of 2 Holliday junction
- - - - Ends of chromosomes that comprise of non-coding sequence repeats
      - Fundamental in protecting cells from recombination and damage
      - Telomeres consist of strong bonds within the G quadruplex, and between stacked G quadruplexes
        
        Function to stabilize the ends of the ends of the chromosome
    - - To lessen the end replication problem
      - To protect double stranded DNA from nucleases, which can enter and chew the DNA on duplex region
        
        Nucleases are blocked by g-quadruplex form entering DNA molecule on duplex region
    - - All 4 strands are parallel
      - 3 linking trinucleotide loops positioned on exterior of quadruplex core, in a propeller-like arrangement
  - - - Help to stabilize the structure
        Other ions like Mg, Zn and Ca may also be found and can affect the direction of the DNA strands that form the G-Quadruplex