MOLECULAR BIOLOGY OF THE CELL 7TH
EDITION ACTUAL EXAM PAPER 2026
QUESTIONS WITH ANSWERS GRADED A+
⩥ 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
EDITION ACTUAL EXAM PAPER 2026
QUESTIONS WITH ANSWERS GRADED A+
⩥ 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
