18 Flashcards
what are the purines
pure As Gold
what are the pyrimidines
CT
whats a nucleotide
phosphate group, sugar, and base
to what end are new nucleotides added
3´
how many bonds between G and C
3
how many bonds between A and T
2
what type of bon delinks the base pairs
covalent
what kind of bond is in the sugar phosphate backbone
peptide bonds
what free structure is on the 5´end
free phosphate group
what free structure is on the 3´end
unliked OH group on sugar backbone
how many histones does DNA wrap around
8
What is the name of the 8 core histones (and linker histone)
2 H2A 2 H2B 2 H3 and 2 H4 and linker histone H1
at what part of the histones do the modifications occur
tail
what is the main function of histone mofidicaiton
they regulate how tightly histones are bound to DNA and therefore whether the chromatin is in the form of a euchromatin or a heterochromatin
What two molecules control the loops that histones create with DNA
Cohensins and CTCF
how much more compact are chromosomes in metaphase compared to DNA itself
10,000x
at what stage of the cell cycle is the chromosome the densest
during mitosis
if the CC lasted a day, how long would interphase last
22-24 hrs
if the CC lasted a day, how long would mitosis last
30-60mn
Where does DNA replication start
at the origin of replication
what form of chormatin is open
euchromatin
what form of chormatin is closed
heterochromatin
how long does the replication of the whole genome take
8-10 hrs
to which end are nucleotides added
3’
on what strand are Okazaki fragments added
lagging strand
in what phase of the CC does DNA replication occur
S phase
what is the function of topoisomerase and how does it work
Prevents supercoiling by making nicks in DNA to allow it to relax and DNA ligase sticks it back
What are two types of antibiotics that target DNA replication
Fluoroquinolones and Trimethoprim - Sulfamethoxazole
what bacteria is Fluoroquinolones used for? what enzyme does it target
targets topoisomerase in bacteria
Aerobic Gram-positive
Aerobic Gram-negative Some anaerobic Gram-negative species and M.tuberculosis
list names of Fluoroquinolones
Nalidixic acid ciproflaxacin
levofloxacin
gemifloxacin
in what ratio is Trimethoprim - Sulfamethoxazole found
1:5
T:S
what bacteria is Fluoroquinolones used for? what step does it target
Aerobic Gram-positive and Gram-negative species
Target nucleotide synthesis
on average when a cell divides. how many mistakes are made
12-20
What are the two major types of defects in DNA
single strand defect
double strand defect
what is base excision repair
If you have deaminated cytosine it becomes uracil. Uracil DNA glycosylase removes the U then sugar phosphate is removed
And DNA pol adds new nucleotides and DNA ligase seals the nicks
what is nucleotide excision repair
If you have ionizing radiaiton, you can get pyrimidine dimers being fomed not at the sugar phspohate sude base bs other base. Pyrimidine dimer elision. Super dangerous because RNA cant be made correctly.
Basically nuclease breaks DNA at 12 nucletoide stretch in bacteria and 20 nucleotdeis in humansm then helicase removes that nucletodie strech and the DNA pol and DNA ligase replaces that strand with a normal copy
what is mismatch repair
Two main enzymes
• MutS binds to mismatched base pair
• MutL scans nearby DNA for nick and triggers strand removal to the
Mismatch
Muts and mut l bind to msitake mutl scans dna looking for a gap, causing remocal of the strand from the gap to the error and replaces it with a new strand.
what is non homologous end joining
accidental ds break
loss of nucleotides due to degradation from ends
it is linked together despite missing bases
Even though its not the same, its reparied and its function structurally perfectly well.
what is non homologous end joining
accidental ds break
loss of nucleotides due to degradation from ends
Finds sister chromosome and copies it into the gap
what gene is mutation within the NER that causes problems
Xeroderma pigmentosum (XP) mutation in a polymerase
causing
Skin cancer, cellular UV sensitivity, neurological abnormalities
what gene is mutation within the mismatch repair that causes problems
Mutation in MutS, MutL
causes colon cancer
what gene is mutation within the mismatch repair that causes problems
Mutation in MutS, MutL
causes colon cancer
what gene is mutation within the homologous recombination repair that causes problems
BRCA2 mutation causes breast and ovarian cancer
