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ASCP Molecular Biology Certification Exam Questions and Answers
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ASCP Molecular Biology Certification Exam Questions and Answers
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ASCP Molecular Biology CertificationExam Questions and Answers
Pyrimidine - -One carbon ring
Cytosine, Thymine, Uracil
-Purine - -Two carbon rings
Adenine, Guanine
-How are nucleotides joined together? - -Condensation to form
phosphodiester bond
-What is the function of mRNA? - -Carries genetic info out of nucleus
Transcript translated to protein
-What is the function of tRNA? - -Carries aa to ribosome
Anticodon pairs with codon on mRNA strand
-What is the function of rRNA? - -part of ribosome structure
most abundant RNA
coordinated coupling of tRNA to mRNA codons
-Feedback inhibition - -Product of pathway is noncompetitive inhibitor
Binds to allosteric site to slow down rxn b/c too much product
-Exonucleases - -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) - -Restriction enzymes
Cleaves phoshpodiester bonds w/i poly-nt chain
Recognition site is palindromic sequence
Types I-V
-ORI sites - -nt sequence where replication is initiated
-Topoisomerase I - -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 - -cuts both strands of one DNA double helix, passes
another unbroken DNA helix through it, and then reanneals the cut strands
, -Gyrase (topoisomerase II) - -Unwinds supercoiling caused by unwinding at
the rep fork by introducing DSBs
-Helicase - -Breaks H-bonds of double helix at the replication fork
-Primase - -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) - -Binds ssDNA and prevents it
from re-annealing during TXN, replication, repair, and recombination
-Okazaki fragments - -Short fragments of DNA synthesized by DNApol δ
using the lagging strand (3'->5') as a template
-Ligase - -Closes gaps in DNA
Catalyzes phosphodiester bond between 3'OH and 5'P
-What are the steps in DNA replication? - -1. Initiate
2. Elongate
3. Terminate
-Telomeres - -Repeat sequence (TTAGGG) at the ends of chr, protect chr
from degradation
-RNA polymerase - -DNA dependent RNApol
Transcribes DNA template to RNA (3'-->5'; anti-parallel)
-Splicesomes - -Complex of snRNPs
Removes introns from pre-mRNA and splices exons together
-Enhancers - -Short regions of DNA that bind proteins (TXN factors) that
enhance TXN of a gene
-Poly-A tail - -Prevents mRNA from being degraded in cytoplasm
100-250 A's at 3' end
-5' cap - -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 - -tRNAs that carry amino acids
-Ribosomes - -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? - -Acceptor > Peptidyl > Exit
-How is translation initiated? - -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? - -Occurs when stop codon enters A site
Release factor recognizes stop codon, hydrolyzes ester bond with P site,
releasing aa chain
-Reverse transcriptase - -enzyme that transcribes RNA to cDNA (lacks
introns)
RNA --> RNA:DNA --> cDNA (dsDNA)
-Pleiotrophy - -a single gene controls the expression of many phenotypic
traits
ie Sickle Cell Anemia
-cDNA - -intron free complementary DNA
can be inserted into a plasmid
-Vector - -helps carry DNA into cell
ie plasmids, virus
-Open Reading Frame (ORF) - -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 - -Measures amount of light absorbed
Quantitative measurement of [DNA/RNA]
-At what wavelength does DNA and RNA absorb? - -260 nm
-At what wavelength does protein absorb? - -280 nm
-Organic isolation method - -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? - -200C for 2 hrs
30 min in 1M NaOH or quanidinum isothiocyanate
-Hybridization - -2 ssDNA molecules of comp base sequence can form a ds
hybrid (duplex)
-What does the incubation step in hybridization do? - -Allows formation of
ds molecules
-Blocking DNA (Hybridization) - -minimizes probe binding to nonspecific
sequence
ie salmon sperm DNA, Human LINE-1
-Blocking Proteins (Hybridization) - -minimize nonspecific binding of probe
to membrane
ie casein (milk), Denhardt's sol
-Stringency - -conditions of hybridization that control the specificity of
binding of the probe to the target sequence
-How can you increase strigency in a hybridization? - -decrease [salt]
increase [formamide]
increase temp
-Formamide acts as a __________ in a hybridization. - -denaturing agent
-Line Probe Assay (LiPA) - -reverse hybridization assay using sequence-
specific oligonucleotide probes (reverse SSOP)
multi-parameter testing --> single strip
-Line Probe Assay steps - -1. Isolate nucleic acid (RNA)
2. Amplify
3. Hybridization
4. Strigent wash
5. Incubate with conjugate
6. Incubate with substrate
7. Detect
-What method would you use if you knew the gene sequence and the
mutation? - -Reverse Dot Blot
-Microarrays - -Used for unknown gene and mutation
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