Pyrimidine
One carbon ring
Cytosine, Thymine, Uracil
Purine
Two carbon rings
Adenine, Guanine
00:03
01:10
How are nucleotides joined together?
Condensation to form phosphodiester bond
What is the function of mRNA?
Carries genetic info out of nucleus
Transcript ...
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ASCP Molecular Biology Certification
Exam
Pyrimidine - Answer One carbon ring
Cytosine, Thymine, Uracil
Purine - Answer Two carbon rings
Adenine, Guanine
How are nucleotides joined together? - Answer Condensation to form phosphodiester
bond
What is the function of mRNA? - Answer Carries genetic info out of nucleus
Transcript translated to protein
What is the function of tRNA? - Answer Carries aa to ribosome
Anticodon pairs with codon on mRNA strand
What is the function of rRNA? - Answer part of ribosome structure
most abundant RNA
coordinated coupling of tRNA to mRNA codons
Feedback inhibition - Answer Product of pathway is noncompetitive inhibitor
Binds to allosteric site to slow down rxn b/c too much product
Exonucleases - Answer 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) - Answer Restriction enzymes
Cleaves phoshpodiester bonds w/i poly-nt chain
Recognition site is palindromic sequence
Types I-V
ORI sites - Answer nt sequence where replication is initiated
Topoisomerase I - Answer 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 - Answer cuts both strands of one DNA double helix, passes another
unbroken DNA helix through it, and then reanneals the cut strands
,Gyrase (topoisomerase II) - Answer Unwinds supercoiling caused by unwinding at the
rep fork by introducing DSBs
Helicase - Answer Breaks H-bonds of double helix at the replication fork
Primase - Answer 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) - Answer Binds ssDNA and prevents it
from re-annealing during TXN, replication, repair, and recombination
Okazaki fragments - Answer Short fragments of DNA synthesized by DNApol δ using
the lagging strand (3'->5') as a template
Ligase - Answer Closes gaps in DNA
Catalyzes phosphodiester bond between 3'OH and 5'P
What are the steps in DNA replication? - Answer 1. Initiate
2. Elongate
3. Terminate
Telomeres - Answer Repeat sequence (TTAGGG) at the ends of chr, protect chr from
degradation
RNA polymerase - Answer DNA dependent RNApol
Transcribes DNA template to RNA (3'-->5'; anti-parallel)
Splicesomes - Answer Complex of snRNPs
Removes introns from pre-mRNA and splices exons together
Enhancers - Answer Short regions of DNA that bind proteins (TXN factors) that enhance
TXN of a gene
Poly-A tail - Answer Prevents mRNA from being degraded in cytoplasm
100-250 A's at 3' end
5' cap - Answer 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 - Answer tRNAs that carry amino acids
Ribosomes - Answer 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? - Answer Acceptor > Peptidyl > Exit
How is translation initiated? - Answer 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? - Answer Occurs when stop codon enters A site
Release factor recognizes stop codon, hydrolyzes ester bond with P site, releasing aa
chain
Reverse transcriptase - Answer enzyme that transcribes RNA to cDNA (lacks introns)
RNA --> RNA:DNA --> cDNA (dsDNA)
Pleiotrophy - Answer a single gene controls the expression of many phenotypic traits
ie Sickle Cell Anemia
cDNA - Answer intron free complementary DNA
can be inserted into a plasmid
Vector - Answer helps carry DNA into cell
ie plasmids, virus
Open Reading Frame (ORF) - Answer 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 - Answer Measures amount of light absorbed
Quantitative measurement of [DNA/RNA]
At what wavelength does DNA and RNA absorb? - Answer 260 nm
At what wavelength does protein absorb? - Answer 280 nm
Organic isolation method - Answer 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
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