DNA Replication Flashcards
Deoxyribose Structure (outline)
5 carbon sugar (1’ to 5’) On C 2’ there’s a H molecule
Ribose Structure (outline)
5 Carbon sugar. On C 2’ there’s a hydroxyl (OH) group
Purine Bases
2 Rings. Adenine and Guanine
Pyrimidine Bases
1 base. Thymine/Uracil and Cytosine
Names of the 3 phosphates
Alpha, beta and gamma
Nucleotide structure
Sugar, Base and 3 Phosphates
5’ end of DNA strand
c 5’ isn’t linked to neighboring structure at posphate molecule
3’ end of DNA
Not linked to other sugar
DNA structure
Double strand one in an antiparallel orientation (opposite directions). Opposite strands have complementary basepairs. A and T (2H) and C and G (3H)
Strongest covalent bond in DNAnstructure
3’ to 5’ phosphodiester. DNA backbone
Strongest non-covalent in DNA structure
Van der Waals. Between base pairs. Bonding is weaker between A and T (less H bonds) then G and C
Karyotype Def.
Constitution and number of chromosome
Number of Chromosomes In Average Human
- 22 pairs of autosomes and 1 pair sex chromosomes
How Chromatin is organised
146 base pairs are wrapped about nucleosome (8 combined histones proteins). Very compact
How DNA can loosen around histones
Acetylation - positive charge on histone (on lysine tails) is neutralised. Negatively charged DNA is less attached. Makes transcription easier
Acetylation Promoter Enzyme
Histone acetyl-transferase. Add acetyl group to histone to neutralise
Acetylation REverse Enzyme
Histone Deacetylase. Removes acetyl from histone
Histone Deacetylase Inhibitor Outline
Vorionostat. Keep acetyl group on histones leaving DNA loosely bound. Allows silenced genes to function. Causes cancer cell death in cutaneous T-cell lymphoma
Chromosome Structures
Centromeres (kinetocore and spindles attach here, repetitive DNA sequences), dark/light bands (foldings) and telomers (cap at chromosome ending, maintain structural integrity)
Heterochromatin Outline
Dark staining. Highly condensed chromatin folding, gene poor. No transcription
Euchromatin Def.
Light staning. Chromatin is more extended the folding, gene rich. Active transcription
% of protein coding DNA (genes/extrons)
1.5%. Highly conserved
Highly Conserved DNA Outline
DNA kept the same across generations and species
% of mitochondrial DNA
5%. Mitochondrial DNA loops.
Parts of Genes
Promoter Elements (proximal + core), 5’ untranslated region, exons, introns, 3’ untranslated region
Promoter Elements Function
Recruits proteins eg RNA polymerase 2
5’ and 3’ UTR Functions
mRNA stability
Exons Function
Amino Acid Coding
Introns Function
Unknown. Speculated splicing
Cell Cycle
G0, G1, S, G2, Mitosis and cytokinesis
Why Chromosomes are Structurally complex
When DNA’s replicated nucleosomes are disassembled and daughter strands are reassembled. Random distribution of old + new histones
DNA Replication Requirements
Single strand template, deoxyribonucleotides triphosphates and Mg^2+
Replisome Def.
Nucleoprotein Complex coordinates replication enzymes and protein, primer and free 3’ hydroxtl end
Primer Def.
RNA molecule helps begin DNA processes
Origins of Replication Def
Short AT rich regions on DNA where initiation begins. Multiple sites in eukaryotes. 2 replicating molecules move outwards from site in different directions. Replicons grow outwards and fuse forming 2 different strands
DNA Helicase Def.
Donut shaped. Wraps around and pulls helix apart
Single Strand Binding Proteins Def.
Attract DNA strands when separate to keep them apart
Topoisomerase Def.
Pulls apart DNA to prevent tightening and breaking of DNA helix and helix unwinds
DNA Polymerase Function
Reads DNA strand template (3’ to 5’), makes complementary DNA strand (5’ to 3’) by aligning nucleotides along templates, catalyses phosphodiester bond formation
Profilerating Cell Nuclear Anigen Function
Holds polymerase in place around DNA
How errors are prevented in DNA Replication
Substrate Specificiy: DNA polymerase only catalysing when compleentary base + proof reading via exonuclease (removes 3’ end nucleoyides)
How strands are simultaneously replicated despite RNA moving in 1 direction
Leading strand is synthesised continuosly by RNA and lagging strand is synthesised discoutinuely by different primases
POlymerase Alpha Function
Instantly replicates DNA vis extending primer 5’ to 3’. No proof reading
Polymerase Gamma Function
Leading strand synthesis via replicating DNA by extending 5’ to 3’. Has proof reading
Polymerase Delta Function
Lagging strand synthesis via extending 5’ to 3’. Has proof reading
Rnase H1 Function
Removes most alpha polymerase except 1 5’ ribonucleotide. Removes flaws
Flap endonuclease 1
removes final 5’ ribonucleotide
