BCHM 4360 ACTUAL EXAM 3 2025 VERIFIED RATIONALES WITH COMPLETE
SOLUTIONS GRADED A
Splicing machinery
Elongation leads to more phosphorylation of CTD, which recruits
Cleavage and polyadenylation complex
Elongation also leads to recruitment of the
Nucleus
Transcription and processing of eukaryotic mRNA occurs in the
Cytoplasm
Translation occurs in the
Exported
Mature mRNAs must be ______________ from the nucleus
Polyadenylation
The protein factors needed for transport are loaded onto the mRNA during transcription,
but __________________ is needed before the RNA-protein complex can be released from
the transcription complex
,Localization elements
Some mRNAs are located in specific regions of the cytoplasm, this requires
______________________, usually found at the 3' end -- they also regulate translation
snoRNAs and certain miRNAs
Most introns do not contain genes and are excised and degraded. Exceptions are
Transesterification
Some introns are removed by proteins, some by RNPs, and some excise themselves. All
mechanisms use ______________________ reactions
Eukaryotes
Introns are far more prevalent in _____________________
Exon shuffling
Introns allow for ____________________, where exons are exchanged and reordered via
recombination, allowing evolution of different genes
Same
Differential removal of introns gives different transcripts from the _______________ gene
,Two
The two exons on either side of an intron are joined in a __________ step process
Exon 1
The intron is first detached from ___________ then it reacts with exon 2
Spliceosome
Most introns are removed by a complex called the _________________, but some are self
splicing
Transesterification
Both steps of exon splicing involve ___________________ reactions
A single phosphodiester bond is broken and replaced by another phosphodiester bond of
similar energy
Similar energy
The ____________________ of the two bonds means that the reaction does not require ATP
and it is easily reversible
(transesterification reactions during exon splicing)
, Group I introns
This group of introns are found in bacteria, viruses, microeukaryotes, and plants
120-450
Group I introns are ______________ nucleotides long
Group I introns
Many but not all of this group of introns can excise themselves from the primary transcript
Group I introns
In this group of introns, splice sites are determined by the 3D structure of the intron and by
recognition of a conserved G-U wobble pair
Group I introns
(which group of introns)
In the first transesterification, a free guanosine is the attacking species that detaches the 5'
end of the intron from exon 1
In the second reaction, the released end of exon 1 attacks the intron-exon 2 junction,
joining the two exons together
SOLUTIONS GRADED A
Splicing machinery
Elongation leads to more phosphorylation of CTD, which recruits
Cleavage and polyadenylation complex
Elongation also leads to recruitment of the
Nucleus
Transcription and processing of eukaryotic mRNA occurs in the
Cytoplasm
Translation occurs in the
Exported
Mature mRNAs must be ______________ from the nucleus
Polyadenylation
The protein factors needed for transport are loaded onto the mRNA during transcription,
but __________________ is needed before the RNA-protein complex can be released from
the transcription complex
,Localization elements
Some mRNAs are located in specific regions of the cytoplasm, this requires
______________________, usually found at the 3' end -- they also regulate translation
snoRNAs and certain miRNAs
Most introns do not contain genes and are excised and degraded. Exceptions are
Transesterification
Some introns are removed by proteins, some by RNPs, and some excise themselves. All
mechanisms use ______________________ reactions
Eukaryotes
Introns are far more prevalent in _____________________
Exon shuffling
Introns allow for ____________________, where exons are exchanged and reordered via
recombination, allowing evolution of different genes
Same
Differential removal of introns gives different transcripts from the _______________ gene
,Two
The two exons on either side of an intron are joined in a __________ step process
Exon 1
The intron is first detached from ___________ then it reacts with exon 2
Spliceosome
Most introns are removed by a complex called the _________________, but some are self
splicing
Transesterification
Both steps of exon splicing involve ___________________ reactions
A single phosphodiester bond is broken and replaced by another phosphodiester bond of
similar energy
Similar energy
The ____________________ of the two bonds means that the reaction does not require ATP
and it is easily reversible
(transesterification reactions during exon splicing)
, Group I introns
This group of introns are found in bacteria, viruses, microeukaryotes, and plants
120-450
Group I introns are ______________ nucleotides long
Group I introns
Many but not all of this group of introns can excise themselves from the primary transcript
Group I introns
In this group of introns, splice sites are determined by the 3D structure of the intron and by
recognition of a conserved G-U wobble pair
Group I introns
(which group of introns)
In the first transesterification, a free guanosine is the attacking species that detaches the 5'
end of the intron from exon 1
In the second reaction, the released end of exon 1 attacks the intron-exon 2 junction,
joining the two exons together
