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.
על החפיסה הזו
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.
הכרטיסים בחפיסה הזו
כרטיס 1
שאלה
What do you call the RNA precursor that’s processed into mature mRNA?
תשובה
Pre-mRNA, or precursor messenger RNA.
כרטיס 2
שאלה
Can an exon contain bases in the 5′ untranslated region of a mature mRNA?
תשובה
Yes. The 5′ untranslated region stays in the mature mRNA upstream of the translation start site.
כרטיס 3
שאלה
What two changes happen to a pre-mRNA segment when the intron between two exons is spliced out?
תשובה
The intron is removed, and the two flanking exons are joined.
כרטיס 4
שאלה
In ordinary splicing within one pre-mRNA, what happens to the 5′ → 3′ order of the exons that are kept?
תשובה
They stay in their original order. Splicing can change which exons are present.
כרטיס 5
שאלה
Write the mature RNA fragment, 5′ → 3′, after removing intron I1.
Pre-mRNA 5′ → 3′ E1 CACU | I1 GUAAG | E2 UUGCתשובה
5′-CACUUUGC-3′Join CACU to UUGC.
כרטיס 6
שאלה
What is an exon–exon junction in a spliced RNA?
תשובה
The point where the end of one exon joins the start of the next exon in that RNA.
כרטיס 7
שאלה
How can alternative splicing produce different RNA isoforms from the same gene?
תשובה
Different splice patterns keep different parts of the precursor RNA, producing distinct mature RNA versions called isoforms.
כרטיס 8
שאלה
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?
תשובה
10 bases. The two exons contribute 6 + 4.
כרטיס 9
שאלה
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?
תשובה
Exon skipping. The second RNA skips E2 and joins E1 directly to E3.
כרטיס 10
שאלה
Remove both introns. What’s the resulting RNA fragment, 5′ → 3′?
Pre-mRNA 5′ → 3′ E1 ACUG | I1 GUCAG | E2 CAA I2 GUUAG | E3 GGUAתשובה
5′-ACUGCAAGGUA-3′Join E1, E2, and E3 in that order.
כרטיס 11
שאלה
A mature RNA fragment consists of exons E1, E2, and E4 in that 5′ to 3′ order. Which exon–exon junctions does it contain?
תשובה
E1 → E2 and E2 → E4. Each junction connects adjacent exons in the mature fragment.
כרטיס 12
שאלה
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 → E3תשובה
Isoform A. It places E2 immediately before E3.
כרטיס 13
שאלה
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?
תשובה
It decreases by 7 bases. The difference is the length of the skipped exon.
כרטיס 14
שאלה
What does intron retention mean when comparing mature RNA isoforms?
תשובה
A sequence removed as an intron in one splice form remains in another mature form.
כרטיס 15
שאלה
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 CUGAתשובה
5′-GGACGUACAGAUUCCUGA-3′Keep E1–I1–E2 together and join E2 to E3.
כרטיס 16
שאלה
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 GCUUAתשובה
5′-AC|GC-3′Take the last two bases of E1 and the first two of E2.
כרטיס 17
שאלה
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 → E3תשובה
Isoform B. Joining E1 directly to E3 gives
GAGCUUACC.כרטיס 18
שאלה
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?
תשובה
Isoform B is 11 bases longer. Counting both endpoints gives 47 − 37 + 1 = 11 retained bases.
כרטיס 19
שאלה
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?
תשובה
No. The same stretch can occur in a precursor whose intron hasn’t been removed yet. You need evidence that the RNA is mature.
כרטיס 20
שאלה
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 UAGGתשובה
5′-UCCAUAGG-3′Only E1 and E3 contribute bases.
כרטיס 21
שאלה
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 AGCCתשובה
Positions 7 and 8. E1 ends at base 7, and E2 starts at base 8.
כרטיס 22
שאלה
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 → E4תשובה
No. Both contain E1 → E2. A junction such as E2 → E4 would distinguish B from A.
כרטיס 23
שאלה
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 → E4תשובה
Isoform B. Its exons total 4 + 3 + 5 = 12 bases. Isoform A has 14.
כרטיס 24
שאלה
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 CCUUAתשובה
GCC. The second codon uses the last G of E1 and the first two Cs of E2.כרטיס 25
שאלה
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 CUUGתשובה
5′-AAGCCUUG-3′The proposed answer puts E2 before E1.
כרטיס 26
שאלה
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 AUCGAתשובה
5′-GCU|A-3′The left side comes from the end of E1, and the right side starts E3.
כרטיס 27
שאלה
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 → E4תשובה
Neither. Each candidate keeps an exon between E1 and E4.
כרטיס 28
שאלה
A student counts 10 RNA bases in
5′-GAUC|CUGAA-3′by including the | that marks the join. What’s the base count?תשובה
9 bases. There are 4 bases before the junction and 5 after it.
כרטיס 29
שאלה
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?
תשובה
No. Those junctions fall outside the translated sequence, so the two RNAs can encode the same amino acid sequence.
כרטיס 30
שאלה
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 GGCUתשובה
5′-ACCGGUCUAGUGAGGCU-3′Restore the retained I1 sequence between E1 and E2.
כרטיס 31
שאלה
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 CUUGUתשובה
5′-GACA|CUUGU-3′The boundary follows all four bases of E1.
כרטיס 32
שאלה
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 → E3תשובה
No. Both candidates contain CGAC inside their shared E1 sequence.
כרטיס 33
שאלה
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 → E4תשובה
No. Both total 13 bases. The sequence or a mapped junction could distinguish them.
כרטיס 34
שאלה
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 UCAGתשובה
UUC. The codon uses the last U of E1 and the first two bases of E3.כרטיס 35
שאלה
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 AUGCCUתשובה
5′-UACGAAUGCCU-3′Include the untranslated exon in the mature RNA.
כרטיס 36
שאלה
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 → E3תשובה
E2 → E3. Retained I1 still lies between E1 and E2.
כרטיס 37
שאלה
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 → E3תשובה
Both. AUGC lies within E2 in A and crosses E1 → E3 in B.
כרטיס 38
שאלה
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.תשובה
11 bases longer. A includes the 6 bases of I1 and the 5 bases of E2 that B lacks.
38 כרטיסים
RNA Splicing Flashcards: Exon Junctions & Isoforms
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