BCHM 4360 EXAM SCRIPT 2026
COMPLETE QUESTIONS AND SOLUTIONS
GRADED A+
◉Double-strand Break (DSB). Answer: A break in both strands of
DNA requiring repair to maintain genome stability
◉End resection. Answer: Degradation of 5' DNA ends to create 3'
single-stranded overhangs during HR.
◉3' Overhang. Answer: Single-stranded DNA used to invade
homologous DNA during recombination.
◉Strand invasion. Answer: Process where ssDNA pairs with
homologous duplex DNA to initiate repair
◉D-loop. Answer: Displacement loop formed when invading DNA
strand pairs with homologous template.
◉Rad51. Answer: Eukaryotic protein that mediates strand invasion
during homologous recombination.
,◉RecA. Answer: Bacterial homologous of Rad51 that promotes
homologous recombination.
◉Holiday junction. Answer: Cross-shaped DNA structure formed
during homologous recombination.
◉Crossover recombination. Answer: Exchange of genetic material
between DNA molecules after Holliday junction resolution.
◉Non-crossover recombination. Answer: Repair without exchange
of chromosome arms.
◉Homologous recombination vs NHEJ. Answer: HR uses template
and is accurate; NHEJ directly legates DNA and is error-prone
◉CRISPR. Answer: Cluster Regularly Interspaced Short Palindromic
Repeats forming bacterial adaptive immunity.
◉Cas9. Answer: RNA-guided endonuclease that creates double
strand DNA breaks.
◉Guide RNA (gRNA). Answer: RNA molecule directing Cas9 to a
specific DNA sequence.
, ◉crRNA. Answer: RNA containing target sequence information.
◉TracrRNA. Answer: RNA that binds Cas9 and stabilizes crRNA.
◉PAM sequence. Answer: Short DNA motif required for Cas9
binding and cleavage (e.g., NGG).
◉CRISPR double-strand break outcome. Answer: Determined by
cellular repair pathway, not Cas9 itself
◉NHEJ repair. Answer: Error-prone repair causing insertions or
deletions (gene knockout)
◉HDR (homology-directed repair). Answer: Precise repair using
donor template for gene editing.
◉Gene knockout. Answer: Loss of gene function typically caused by
NHEJ indels.
◉Gene knock-in. Answer: Precise insertion achieved through
homologous recombination.
COMPLETE QUESTIONS AND SOLUTIONS
GRADED A+
◉Double-strand Break (DSB). Answer: A break in both strands of
DNA requiring repair to maintain genome stability
◉End resection. Answer: Degradation of 5' DNA ends to create 3'
single-stranded overhangs during HR.
◉3' Overhang. Answer: Single-stranded DNA used to invade
homologous DNA during recombination.
◉Strand invasion. Answer: Process where ssDNA pairs with
homologous duplex DNA to initiate repair
◉D-loop. Answer: Displacement loop formed when invading DNA
strand pairs with homologous template.
◉Rad51. Answer: Eukaryotic protein that mediates strand invasion
during homologous recombination.
,◉RecA. Answer: Bacterial homologous of Rad51 that promotes
homologous recombination.
◉Holiday junction. Answer: Cross-shaped DNA structure formed
during homologous recombination.
◉Crossover recombination. Answer: Exchange of genetic material
between DNA molecules after Holliday junction resolution.
◉Non-crossover recombination. Answer: Repair without exchange
of chromosome arms.
◉Homologous recombination vs NHEJ. Answer: HR uses template
and is accurate; NHEJ directly legates DNA and is error-prone
◉CRISPR. Answer: Cluster Regularly Interspaced Short Palindromic
Repeats forming bacterial adaptive immunity.
◉Cas9. Answer: RNA-guided endonuclease that creates double
strand DNA breaks.
◉Guide RNA (gRNA). Answer: RNA molecule directing Cas9 to a
specific DNA sequence.
, ◉crRNA. Answer: RNA containing target sequence information.
◉TracrRNA. Answer: RNA that binds Cas9 and stabilizes crRNA.
◉PAM sequence. Answer: Short DNA motif required for Cas9
binding and cleavage (e.g., NGG).
◉CRISPR double-strand break outcome. Answer: Determined by
cellular repair pathway, not Cas9 itself
◉NHEJ repair. Answer: Error-prone repair causing insertions or
deletions (gene knockout)
◉HDR (homology-directed repair). Answer: Precise repair using
donor template for gene editing.
◉Gene knockout. Answer: Loss of gene function typically caused by
NHEJ indels.
◉Gene knock-in. Answer: Precise insertion achieved through
homologous recombination.
