Nucleic Acids

oiv01's version from 2016-02-15 03:27


Question Answer
purinetwo membered ring, adenine (A) and guanine (G)
pyrimidineone ring, cytosine (C), Thymine (T), Uracil (U, in RNA)
nucleosideribose + base
nucleotideribose + base + phosphates
nucleotides linked by what?phosphodiester bond
AZTblocks nucleic synthesis of AIDs virus , 3'-OH group replaced by azido group, analog of thymidine, AZT lacks the 3’-OH that replication would add to, once AZT is attached to the end of a DNA chain, no further DNA synthesis can take place
dna strands are parellel or antiparellel?antiparellel
major grooveinteracts w/ specific transcription factors
minor grooveinteracts w/ histone molecules
Z-DNAzig-zag helical structure, 12 bases/turn, found in regions of active transcription
B-DNAsmooth helix turns, 10.4 bases/turn, predominant
A-DNAsmooth helix turns, 11 bases/turn, DNA-RNA hybrids
genes that codes for the large ribosomal RNAs13, 14, 15, 21, and 22
dimensions of DNA in our cells1.8 meters long, 6 uM in diameter
chromatinprotein assoc. dna; forms several hierarchical levels of folding to achieve necessary compaction
first level of DNA packagingnucleosome (nucleosome core: dna + histone octamer)
histone octamer2X (H2A, H2B, H3, H4); dissociated histone core
histonemost abundant, tightly assoc. chromatin proteins, small and highly basic proteins
core histonesH2A, H2B, H3, H4
linker histonesH1/5
domain structureglobular core w/ histone fold, unstructured N-terminal tails
regulation of chromatin? post-translational modification of histones
Question Answer
HAC, histone acetylaseoccurs on lysine residues, changes electrostat. interactions b/t histones and dna; increased acetylation-->inc. dna accessibility, transcription, replication/repair
HDAC, histone deacetylasedecreased acetylation=decreased transcription of dna, decreases accesibility
second level of dna packaging30 nM filaments
formation of 30 nM filamentsin vitro, reversible, regulated by Na+/Mg2+ conc., requires core histone N-terminal tails, inhibited by tail acetylation, stabilized by H1 presence
H3 serine 10 phosphorylation?chromosome condensation
serine 10 mutation leads to ?defects in chromosome condensation and segregation
linkersmall stretch of dna running b/t adj. nucleosome cores, binds by histone H1
nucleosomeone nucleosome core plus a linker
H1histone protein present as monomer w/i the nucleosome, not a part of the core particle
major scaffold proteinstopoisomerase II, nuclease (prevent dna tangling), structural maintenance of chromosomes (SMC) proteins
SMC proteins large family of ATPases that participate in many aspects of higher-order chromosome organization and dynamics; present in condensin and cohesin
cohesinshelp hold sister chromatids together
condensininvolved in chromosome condensation


Question Answer
7 steps of dna replicationinitiation, extension, unwinding, processive synthesis to make long chains, coordination of leading and lagging strand synthesis, fidelity, termination
dna featuresrecog./bound by trans-acting factors, contain short region of high A/T content facilitates melting (Dna strand separation), often contains palindromic sequences (inverted repeates), small in bacteria, complex/arge in metazoans
helicaseunwinds dna
dna ligaseseals dna gaps; connects free 3' OH group to free 5' phosphate group to create phosphodiester bond
leading strandcontinuous elongation, direction of synthesis AND direction of chain growth is 5' to 3',
lagging strandtemplate runs anti-parellel, direction of synthesis is 5' to 3', chain growth is 3' to 5', discontinuous growth=okazaki frags; dna pol alpha completes strand after telomerase comes in
topisomerase relieves torsional strain on parental duplex caused by unwinding, bind to DNA and cuts phosphate backbone of the DNA; intermediate break allows DNA to be untangled/unwound
rna primerdna polymerase can't perform de novo dna synthesis, so rna primer is synth. during replication
primaseenzyme that synthesizes short rna primers using dna as a template; starts new chain by joining 2 nucleoside triphosphates together in 5' to 3' direction; 3' end of primer available for dna polym. to continue dna synth.
elongationdNTP +primer, PPi + primer released, dna-dependent dna polymerase is enzyme, formation of phosphodiester bond takes place (catalytic step), nucleophilic attach by 3' OH of sugar
sliding clampprotein fold that binds dna polymerase and prevents enzyme from dissociating from the template dna strand, inc. rate of dna synthesis 1000-fold; ex: proliferating cell nuclear antigen (PCNA)
rate limiting step in dna synth. rxn?association of the polymerase w/ the dna template
dna polymeraseresponsible for duplication, require a template and primer (dna primase), 5' to 3', low affinity for DNA, increased accuracy slows extension, fills in gaps of okazaki frags
Pol IIIimportant for proofreading, involved in replication, 3' to 5' exonuclease activity!
Pol deltamajor dna replication enzyme
Pol alphastarts synthesis of the lagging strand; polymerizes short dna for the primer before Pol delta come to take over
pol gammadna replication in mitochondria
RNase Hremoves primers, hydrolyzes RNA of DNA-RNA hybrids
FEN1flap endonucleases 1, aids in removing primers by recognizing unannealed portion of rna near 5' end
telomeraseperforms replication of dna ends, contains and rna and an reverse transcriptase; rna base pairs w/ the overhanging 3' end of telomeres, extends it, repeats, dna polym. complete the fill in process


Question Answer
Year Watson and Crick determined DNA structureApril 25,1953
Info used to construct model1. chemical structure & molecular dimensions of deoxyribose, bases, & P 2. Chargaff's finding that DNA has equivalent amounts of A to T and C to G 3. X-ray diffraction patterns of DNA by Franklin 4.
Mendelpublished basic rules of inheritance by growing peas
3 general rules of inheritance1. info in DNA directs fxt of cell & is transmitted to offspring during replication & replication utilizes complementary pairing of bases 2. DNA directs cell processes through synthesis of RNA which occurs through complementary pairing of ribonucleotide bases 3. several types of RNA are invovled to synthesize enzymes, proteins, and polypeptides
Kosseldetemined DNA chemical composition
Leventhought DNA was a small molecule
Erwin Griffith (1928) transformation principalmolecules that can carry heritable information are present in S strain cells - experimented with Pneumococcus
Avery-Macleod-Mcarty (1944)the molecule that carries the heritable information is DNA - experimented with enzyme treatment
Hershey and Chase (1952)demonstrated via radioactive labeling that DNA was present in the progenies of viruses and was definitively the genetic material - experimented with bacteriophage T2


Question Answer
Central Dogma of Molecular BiologyDNA ----> DNA (copy) -----> RNA -----> PROTEIN
3 dogma processes1. Replication 2. Transcription 3. Translation