RNA Splicing Flashcards: Exon Junctions & Isoforms
Practice RNA splicing in 38 flashcards. Assemble mature mRNA, compare exon skipping and intron retention, and use exon junctions to tell isoforms apart.
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Start with a labeled pre-mRNA fragment and work out what stays in mature RNA. These 38 original English RNA splicing flashcards are for upper-secondary and introductory college biology learners who already read RNA in the 5′ → 3′ direction.
Use stated splice patterns to write mature fragments or calculate their lengths. Practice removing introns, skipping an exon, retaining an intron, and keeping an untranslated exon. Use exon order or sequence to name the junctions, locate a junction by base position, and take a short sequence window across it. Then work backward from a mapped junction, a sequence fragment, or length to decide which listed isoforms fit. Some observations match both models or neither. A few cards ask you to repair a proposed answer or group a codon across a join from a supplied start.
The order introduces pre-mRNA, exons, introns, and exon order before the first sequence exercise. It then mixes assembly, junction, length, and evidence checks, so you revisit each kind of task on new examples. The short RNA fragments are invented and model only the stated splice choices. Predicting splice sites from raw sequence takes additional evidence, and a mature fragment alone can’t reveal the sequences that were removed. Spliceosome chemistry and full protein prediction are outside this boundary and isoform drill. For worked examples, see the RNA splicing practice lesson.
The cards and examples were written independently with AI assistance. Factual references include the NHGRI RNA fact sheet, Dittmar et al. on alternative splicing, and Middleton et al. on intron retention. Original material, including the AI-generated decorative cover, is dedicated under CC0 1.0 to the extent applicable rights exist.
Tarjetas de este mazo
Tarjeta 1
Pregunta
What do you call the RNA precursor that’s processed into mature mRNA?
Respuesta
Pre-mRNA, or precursor messenger RNA.
Tarjeta 2
Pregunta
Can an exon contain bases in the 5′ untranslated region of a mature mRNA?
Respuesta
Yes. The 5′ untranslated region stays in the mature mRNA upstream of the translation start site.
Tarjeta 3
Pregunta
What two changes happen to a pre-mRNA segment when the intron between two exons is spliced out?
Respuesta
The intron is removed, and the two flanking exons are joined.
Tarjeta 4
Pregunta
In ordinary splicing within one pre-mRNA, what happens to the 5′ → 3′ order of the exons that are kept?
Respuesta
They stay in their original order. Splicing can change which exons are present.
Tarjeta 5
Pregunta
Write the mature RNA fragment, 5′ → 3′, after removing intron I1.
Pre-mRNA 5′ → 3′ E1 CACU | I1 GUAAG | E2 UUGCRespuesta
5′-CACUUUGC-3′Join CACU to UUGC.
Tarjeta 6
Pregunta
What is an exon–exon junction in a spliced RNA?
Respuesta
The point where the end of one exon joins the start of the next exon in that RNA.
Tarjeta 7
Pregunta
How can alternative splicing produce different RNA isoforms from the same gene?
Respuesta
Different splice patterns keep different parts of the precursor RNA, producing distinct mature RNA versions called isoforms.
Tarjeta 8
Pregunta
A pre-mRNA fragment has a 6-base exon, a 9-base intron, and a 4-base exon in that order. How many bases remain after the intron is removed?
Respuesta
10 bases. The two exons contribute 6 + 4.
Tarjeta 9
Pregunta
One mature RNA has exons E1 → E2 → E3. A second mature RNA from the same precursor has E1 → E3. What event accounts for the difference?
Respuesta
Exon skipping. The second RNA skips E2 and joins E1 directly to E3.
Tarjeta 10
Pregunta
Remove both introns. What’s the resulting RNA fragment, 5′ → 3′?
Pre-mRNA 5′ → 3′ E1 ACUG | I1 GUCAG | E2 CAA I2 GUUAG | E3 GGUARespuesta
5′-ACUGCAAGGUA-3′Join E1, E2, and E3 in that order.
Tarjeta 11
Pregunta
A mature RNA fragment consists of exons E1, E2, and E4 in that 5′ to 3′ order. Which exon–exon junctions does it contain?
Respuesta
E1 → E2 and E2 → E4. Each junction connects adjacent exons in the mature fragment.
Tarjeta 12
Pregunta
A mature RNA fragment contains a mapped E2 → E3 junction. Which candidate isoform matches?
Mature exon orders, 5′ → 3′ A: E1 → E2 → E3 B: E1 → E3Respuesta
Isoform A. It places E2 immediately before E3.
Tarjeta 13
Pregunta
An mRNA isoform skips a 7-base exon. Compared with the isoform that includes it, how does the RNA length change if everything else is identical?
Respuesta
It decreases by 7 bases. The difference is the length of the skipped exon.
Tarjeta 14
Pregunta
What does intron retention mean when comparing mature RNA isoforms?
Respuesta
A sequence removed as an intron in one splice form remains in another mature form.
Tarjeta 15
Pregunta
A mature RNA isoform keeps I1 and removes I2. Write this fragment 5′ → 3′.
Pre-mRNA 5′ → 3′ E1 GGAC | I1 GUACAG | E2 AUUC I2 GUGAG | E3 CUGARespuesta
5′-GGACGUACAGAUUCCUGA-3′Keep E1–I1–E2 together and join E2 to E3.
Tarjeta 16
Pregunta
E1 and E2 are joined in this mature RNA fragment. Write the two bases on each side of the junction, with | at the join.
Exon sequences, 5′ → 3′ E1 AGUAC E2 GCUUARespuesta
5′-AC|GC-3′Take the last two bases of E1 and the first two of E2.
Tarjeta 17
Pregunta
The entire modeled mature fragment is
5′-GAGCUUACC-3′. Which of the two splice forms below makes it?Exon sequences, 5′ → 3′ E1 GAGC E2 CUAG E3 UUACC A: E1 → E2 → E3 B: E1 → E3Respuesta
Isoform B. Joining E1 directly to E3 gives
GAGCUUACC.Tarjeta 18
Pregunta
In a pre-mRNA, an intron spans bases 37 through 47, including both endpoints. Mature isoform A removes it, and B retains it. If the rest of the sequence is identical, which isoform is longer and by how many bases?
Respuesta
Isoform B is 11 bases longer. Counting both endpoints gives 47 − 37 + 1 = 11 retained bases.
Tarjeta 19
Pregunta
A fragment contains an intron sequence between its two flanking exons. Does that evidence alone establish that it came from a mature RNA isoform with intron retention?
Respuesta
No. The same stretch can occur in a precursor whose intron hasn’t been removed yet. You need evidence that the RNA is mature.
Tarjeta 20
Pregunta
A mature RNA fragment skips E2 and removes both neighboring introns. Write the fragment 5′ → 3′.
Pre-mRNA 5′ → 3′ E1 UCCA | I1 GUAUG | E2 AGCUA I2 GUGCAG | E3 UAGGRespuesta
5′-UCCAUAGG-3′Only E1 and E3 contribute bases.
Tarjeta 21
Pregunta
In the spliced fragment below, which two base positions meet at the E1 → E2 junction? Count from 1 at the 5′ end.
Exon sequences, 5′ → 3′ E1 CAGUACU E2 AGCCRespuesta
Positions 7 and 8. E1 ends at base 7, and E2 starts at base 8.
Tarjeta 22
Pregunta
A fragment from one of these mature RNAs spans the mapped E1 → E2 junction. Can you tell which candidate it came from?
Mature exon orders, 5′ → 3′ A: E1 → E2 → E3 → E4 B: E1 → E2 → E4Respuesta
No. Both contain E1 → E2. A junction such as E2 → E4 would distinguish B from A.
Tarjeta 23
Pregunta
The full mature fragment is 12 bases long. Which candidate order fits these exon lengths?
E1: 4 bases E2: 5 bases E3: 3 bases E4: 5 bases A: E1 → E2 → E4 B: E1 → E3 → E4Respuesta
Isoform B. Its exons total 4 + 3 + 5 = 12 bases. Isoform A has 14.
Tarjeta 24
Pregunta
Read this mature RNA in triplets from the indicated AUG at its 5′ end. Which codon crosses the E1 → E2 junction?
Exon sequences, 5′ → 3′ E1 AUGG E2 CCUUARespuesta
GCC. The second codon uses the last G of E1 and the first two Cs of E2.Tarjeta 25
Pregunta
After splicing out the intron, a student writes
5′-CUUGAAGC-3′. What’s the correct mature fragment?Pre-mRNA 5′ → 3′ E1 AAGC | I1 GUUGAG | E2 CUUGRespuesta
5′-AAGCCUUG-3′The proposed answer puts E2 before E1.
Tarjeta 26
Pregunta
E2 is skipped. Write the three bases just upstream and the one base just downstream of the new E1 → E3 junction, in 5′ → 3′ order. Mark the join with |.
Exon sequences, 5′ → 3′ E1 CUAGCU E2 UGGG E3 AUCGARespuesta
5′-GCU|A-3′The left side comes from the end of E1, and the right side starts E3.
Tarjeta 27
Pregunta
A mature fragment has a mapped E1 → E4 junction. Which of these two candidate exon orders is compatible?
Mature exon orders, 5′ → 3′ A: E1 → E2 → E4 B: E1 → E3 → E4Respuesta
Neither. Each candidate keeps an exon between E1 and E4.
Tarjeta 28
Pregunta
A student counts 10 RNA bases in
5′-GAUC|CUGAA-3′by including the | that marks the join. What’s the base count?Respuesta
9 bases. There are 4 bases before the junction and 5 after it.
Tarjeta 29
Pregunta
Two RNA isoforms have different exon junctions in their 5′ untranslated regions and identical translated sequences. Does the junction difference by itself imply different amino acid sequences?
Respuesta
No. Those junctions fall outside the translated sequence, so the two RNAs can encode the same amino acid sequence.
Tarjeta 30
Pregunta
This mature isoform retains I1 and removes I2. A student writes
5′-ACCGUGAGGCU-3′. What’s the correct fragment?Pre-mRNA 5′ → 3′ E1 ACCG | I1 GUCUAG | E2 UGA I2 GUAUAG | E3 GGCURespuesta
5′-ACCGGUCUAGUGAGGCU-3′Restore the retained I1 sequence between E1 and E2.
Tarjeta 31
Pregunta
The bases in
5′-GAC|ACUUGU-3′are correct, but the E1 → E2 marker is misplaced. Where should | go?Exon sequences, 5′ → 3′ E1 GACA E2 CUUGURespuesta
5′-GACA|CUUGU-3′The boundary follows all four bases of E1.
Tarjeta 32
Pregunta
A short mature RNA fragment reads
5′-CGAC-3′. Does it distinguish these candidate isoforms?Exon sequences, 5′ → 3′ E1 UCGACG E2 AGUU E3 CUCA A: E1 → E2 → E3 B: E1 → E3Respuesta
No. Both candidates contain CGAC inside their shared E1 sequence.
Tarjeta 33
Pregunta
A complete mature fragment is 13 bases long. Can length alone choose between these candidate exon orders?
E1: 5 bases E2: 4 bases E3: 4 bases E4: 4 bases A: E1 → E2 → E4 B: E1 → E3 → E4Respuesta
No. Both total 13 bases. The sequence or a mapped junction could distinguish them.
Tarjeta 34
Pregunta
Translation starts at the AUG in E1. If the mature isoform skips E2, what codon immediately follows AUG?
Exon sequences, 5′ → 3′ E1 AUGU E2 GCA E3 UCAGRespuesta
UUC. The codon uses the last U of E1 and the first two bases of E3.Tarjeta 35
Pregunta
E1 lies entirely in the 5′ untranslated region. Both exons are kept and I1 is removed. Write the whole mature RNA fragment, 5′ → 3′.
Pre-mRNA 5′ → 3′ E1 UACGA | I1 GUAGAG | E2 AUGCCURespuesta
5′-UACGAAUGCCU-3′Include the untranslated exon in the mature RNA.
Tarjeta 36
Pregunta
In this mature isoform I1 is retained and I2 is excised. Which exon–exon junction is formed within the shown fragment?
Pre-mRNA block order, 5′ → 3′ E1 → I1 → E2 → I2 → E3Respuesta
E2 → E3. Retained I1 still lies between E1 and E2.
Tarjeta 37
Pregunta
A short mature RNA fragment reads
5′-AUGC-3′. Which candidate isoform or isoforms could contain it?Exon sequences, 5′ → 3′ E1 CUCAU E2 UAUGCA E3 GCAU A: E1 → E2 → E3 B: E1 → E3Respuesta
Both. AUGC lies within E2 in A and crosses E1 → E3 in B.
Tarjeta 38
Pregunta
How many bases longer is mature fragment A than B?
Pre-mRNA order, 5′ → 3′ E1 (4) → I1 (6) → E2 (5) → I2 (7) → E3 (3) A keeps E1, I1, E2, and E3. B keeps E1 and E3 only.Respuesta
11 bases longer. A includes the 6 bases of I1 and the 5 bases of E2 that B lacks.
38 tarjetas
RNA Splicing Flashcards: Exon Junctions & Isoforms
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