ASCP MOLECULAR BIOLOGY EXAM
PREP QUESTIONS AND ANSWERS
(GRADED A+)
Pyrimidine - ANSWER-one carbon ring
Cytosine, Thymine, Uracil
Purine - ANSWER-two carbon rings
Adenine, Guanine
How are nucleotides joined together? - ANSWER-condensation
What does mRNA do? - ANSWER-carries code out of cell.
code for protein structure.
DNA to ribosomes
end of transcription start of translation
What does tRNA do? - ANSWER-decodes mRNA. Matches amino acids to mRNA
code. Protein synthesis
What does rRNA do? - ANSWER-part of ribosome structure
most abundant RNA
coordinated coupling of tRNA to mRNA codons
Feedback Inhibition - ANSWER-end 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 nucleotide
at a time
cleaves phosphodiester bond at end of chain
5' ---> 3' and 3' ---> 5'
Endonucleases - ANSWER-cleaves phoshpodiester bonds w/in chain
recognition site is palindromic sequence
cleaves unevenly, leaves sticky ends
(restriction enzymes)
DNA polymerase III - ANSWER-copies DNA by reading existing strand, builds new
comp. strand
always adds to 3' end
can't start new strand on its own (ORI sites)
, enhancers - ANSWER-far from promoter
maintain a tissue-specific or cell-specific level of gene expression
Poly-A tail - ANSWER-keeps mRNA from being destroyed in cytoplasm
at 3' end
piece of 100-250 A's
5' cap - ANSWER-added to 5' end of finished mRNA
let's cell know it's ready for translation
ribosomal binding site
aminoacyl tRNA - ANSWER-tRNAs that carry amino acids
Ribosomes - ANSWER-where mRNAs and tRNAs meet
Large and small form packets (A, P and E)
catalyzes peptide bond formation b/w amino acids by rRNA
ORI sites - ANSWER-origin of replication on chromosome
triggers DNA replication
gyrase - ANSWER-unwinds DNA in front of fork
DNA polymerase I - ANSWER-removes RNA nucleotides form RNA primers and
replaces with DNA
(makes sure primers that start replication are removed)
helicase - ANSWER-breaks H-bonds of double helix
topoisomerase - ANSWER-breaks/ reseals DNA backbone to release tension caused by
twisting
(DNA gyrase)
What is the path of a tRNA in a ribosome? - ANSWER-A ---> P ------> E
How is translation initiated? - ANSWER-small subunit binds to ribosomal binding site
MET anticodon binds to start codon
large subunit binds to small subunit
How is translation terminated? - ANSWER-stop codon is carried into small subunit by
tRNA
recognized by release factor, breaks bond b/w chain and tRNA
released from ribosome and out into cell
reverse transcriptase - ANSWER-enzyme that allows RNA to go to DNA
mRNA --> ssDNA --> cDNA --> dsDNA
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