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ASCP TECHNOLOGIST IN MOLECULAR BIOLOGY BOARD EXAM PREP
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ASCP TECHNOLOGIST IN MOLECULAR BIOLOGYBOARD EXAM PREP
Pyrimidine - Answers -One carbon ring
Cytosine, Thymine, Uracil
Purine - Answers -Two carbon rings
Adenine, Guanine
How are nucleotides joined together? - Answers -Condensation to form phosphodiester
bond
What is the function of mRNA? - Answers -Carries genetic info out of nucleus
Transcript translated to protein
RNA polymerase - Answers -DNA dependent RNApol
Transcribes DNA template to RNA (3'-->5'; anti-parallel)
Splicesomes - Answers -Complex of snRNPs
Removes introns from pre-mRNA and splices exons together
Enhancers - Answers -Short regions of DNA that bind proteins (TXN factors) that
enhance TXN of a gene
Poly-A tail - Answers -Prevents mRNA from being degraded in cytoplasm
100-250 A's at 3' end
5' cap - Answers -5'-5' pyrophosphate bridge to a methylated G added to 5' end of a
mRNA
Protects against degradation and as a recognition signal for TLN apparatus
aminoacyl tRNA - Answers -tRNAs that carry amino acids
Ribosomes - Answers -Where TLN occurs
Prok: 30s and 50s
Euk: 40s and 60s
Catalyzes peptide bond between a.a.'s
What is the path of a tRNA in a ribosome? - Answers -Acceptor > Peptidyl > Exit
How is translation initiated? - Answers -small rRNA (40S) subunit binds mRNA and
scans for start codon (AUG)
Met-tRNA is brought to the P site
,Large rRNA (60S) subunit binds
How is translation terminated? - Answers -Occurs when stop codon enters A site
Release factor recognizes stop codon, hydrolyzes ester bond with P site, releasing aa
chain
Reverse transcriptase - Answers -enzyme that transcribes RNA to cDNA (lacks introns)
RNA --> RNA:DNA --> cDNA (dsDNA)
Pleiotrophy - Answers -a single gene controls the expression of many phenotypic traits
ie Sickle Cell Anemia
cDNA - Answers -intron free complementary DNA
can be inserted into a plasmid
Vector - Answers -helps carry DNA into cell
ie plasmids, virus
Open Reading Frame (ORF) - Answers -sections of DNA that begin with start codons
and end with stop codons
DNA: 5' --> 3'
transcription: 3' --> 5' DNA --> RNA (promoter)
translation: 5' --> 3' mRNA
Spectrophotometer - Answers -Measures amount of light absorbed
Quantitative measurement of [DNA/RNA]
At what wavelength does DNA and RNA absorb? - Answers -260 nm
At what wavelength does protein absorb? - Answers -280 nm
Organic isolation method - Answers -1. Lyse
2. Add phenol/ chloroform > vortex/spin
3. Transfer aqueous layer (top) to new tube
4. Add chloroform:IAA (removes phenol) > vortex/spin
5. Transfer aqueous layer to new tube
6. Add NaOAc and EtOH > vortex/spin
7. Decant
8. Resuspend
How do you inactivate RNases? - Answers -200C for 2 hrs
30 min in 1M NaOH or quanidinum isothiocyanate
Hybridization - Answers -2 ssDNA molecules of comp base sequence can form a ds
hybrid (duplex)
, What is the function of tRNA? - Answers -Carries aa to ribosome
Anticodon pairs with codon on mRNA strand
What is the function of rRNA? - Answers -part of ribosome structure
most abundant RNA
coordinated coupling of tRNA to mRNA codons
Feedback inhibition - Answers -Product of pathway is noncompetitive inhibitor
Binds to allosteric site to slow down rxn b/c too much product
Exonucleases - Answers -Degrades nucleic acids by removing one terminal nt at a time
Cleaves phosphodiester bond at end of chain
5' --> 3' and 3' --> 5'
Endonucleases (Prok) - Answers -Restriction enzymes
Cleaves phoshpodiester bonds w/i poly-nt chain
Recognition site is palindromic sequence
Types I-V
ORI sites - Answers -nt sequence where replication is initiated
Topoisomerase I - Answers -Induces ss breaks
Remove DNA supercoils during TXN and DNA replication; for strand breakage during
recombination; for chr condensation; and to disentangle intertwined DNA during mitosis
topoisomerase II - Answers -cuts both strands of one DNA double helix, passes another
unbroken DNA helix through it, and then reanneals the cut strands
Gyrase (topoisomerase II) - Answers -Unwinds supercoiling caused by unwinding at the
rep fork by introducing DSBs
Helicase - Answers -Breaks H-bonds of double helix at the replication fork
Primase - Answers -DNApol α (DNA dep RNA pol)
adds short segments of complementary
RNA to ssDNA template (primers), serves as starting points for replication
single-strand DNA binding proteins (SSBPs) - Answers -Binds ssDNA and prevents it
from re-annealing during TXN, replication, repair, and recombination
Okazaki fragments - Answers -Short fragments of DNA synthesized by DNApol δ using
the lagging strand (3'->5') as a template
Ligase - Answers -Closes gaps in DNA
Catalyzes phosphodiester bond between 3'OH and 5'P
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