Kandpal Flashcards
Central dogma of molecular biology
DNA –> RNA –> protein
What are the constituents of DNA?
DNA is a polymer of 4 bases and a five carbon sugar (deoxyribose); alternating sugar and phosphodiester bonds create backbone; bound to other strands by hydrogen bonds
M phase
mitosis & cytokinesis
POLI
low processivitiy (DNA repair); for rRNA
POLII
somewhat high processivity;
involved in repair;
for mRNA
POLIII
DNA replication;
for tRNA
In what direction does replication occur?
5’ –> 3’
Topoisomerase I
only cuts one strand
Type II topoisomerase
relieves overwinding; ATP dependent
Primase
synthetsizes an RNA as a primer; absolute requirement for replication!
RNA is removed by
POLI
DNA ligase
seals the gap between okasaki fragments
Novobiocin
binds to the B subunit of gyrase
Rifiampin
binds to beta-subunit of Pol to block initiation
Actinomycin D
acts through blocking movement of RNA polymerase; ring gets stuck b/n 2 GC (minor groove of DNA)
Zidovudine (AZT)
analog of deoxy thymidine; prevents DNA chain elongation by reverse transcriptase
End replication problem
when the replication fork reaches the end there is no place for an RNA primer for the last Okazaki fragment
Telomere
piece of DNA which does not code for any protein but has repeating adenine base pairs; used to seal off ends of chromosomes and facilitate replication
Telomerase
extends the leading strand DNA synthesis into the telomere
Histone
highly alkaline proteins found in eukaryotic cell nuclei; package and order DNA
What is the fundamental subunit of chromatin?
nucleosomes
Heterochromatin
tightly wound, inaccessible
Euchromatin
loose, available
Genomic imprinting
certain genes are expressed in a parent-of-origin specific manner; ex: Prader-Willi and Angelman syndromes
Prader-Willi syndrome
paternal inheritance of a deletion of 15q11-13
Angelman syndrome
maternal inheritance of same deletion as Prader-Willi
Pyrimidine base
Cytosine, Thymine, Uracil; 6-membered ring; two N + 4 Cs
Purine base
Adenine, Guanine; 9-membraned double-ring system; 4 Ns + 5 Cs
Transitions
purine replaced with a purine or a pyrimidine replaced with a pyrimidine
Transversion
purine replaced with a pyrimidine or vice versa
Uracil glycosylase
eukaryotes don’t want uracil in their DNA so this recognizes and cleave it
Misincorporation
creates a distortion in the structure; strand directed mismatch repair decides which strand is correct
Base excision repair
specific base is removed and repaired
Nulceotide excision repair
stretch of DNA strand is removed and new strand with correct base is synthesized
Hereditary nonpolyposis colon cancer (HNPCC)
due to a mismatch repair deficiency; if there is an inherited mutation in one copy of mismatch repair gene, there is a predisposition to this; second copy of gene is spontaneously mutated
DNA polymerase
moves from 3’ - 5’ (same direction as RNA synth); the replicate strand is building in the opposite direction
Promotors of prokaryotes have 3 characteristics:
- -10 sequence
- -35 sequence
- separation between two above
Promotors of eukaryotes are one of 3 types:
- TATA containing: TATA is at -25 and -35
- Initiator containing: initiator is a consensus sequence surrounding the start site of transcription
- TATA-less and initiator-less promotors: GC rich island of about 100 nucleotides upstream of the initiation start site