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End-of-topic test: Transcription and RNA Processing

Unit 6 · Topic 6.3 end-of-topic test

Suggested time: about 46 minutes. Answer everything, then press Submit the test to see the feedback and scoring guides.

Answer every question. For each multiple-choice question, pick one option and press Check; the feedback gives the reasoning. For the free-response questions, write one short sentence for each step of your reasoning, each on its own line, and make every link clear (so, because, therefore). That is what the exam’s ‘paragraph form’ means for you: linked sentences, not bullet points. Then open the scoring guide and mark your own work against it.
Question 1
A table with three columns, minutes after the RNA was made, share of the RNA signal in the nucleus, share in the cytoplasm, and four rowsminutes after the RNA was madein the nucleusin the cytoplasm0100 %0 %1072 %28 %2040 %60 %3012 %88 %
Where the marked RNA is, at four times after it was made.

In a eukaryotic cell, one gene's newly made RNA is marked so that it can be followed. The table shows where the marked RNA is over the next thirty minutes.

Which statement explains the pattern in the table?

Question 2
One RNA strand drawn flat: six sugars on a rail with bases hanging down, the end at the left marked 3′ and the end at the right marked 5′ with a small dot before its first sugarCCGUAC3′5′
An mRNA drawn flat, its ends written.

An mRNA is drawn with its 3′ end at the left, as shown. A ribosome is about to read it.

At which end of the drawn mRNA does the ribosome start?

Question 3
One monospace row: 5′-GAU-3′5′-GAU-3′
The codon, written from its 5′ end.

The codon 5′-GAU-3′ is drawn.

Which anticodon pairs with this codon?

Question 4
A table with three columns, RNA, shape, what it does, and four rows lettered W, X, Y, ZRNAshapewhat it doesWone open strand, thousands of nucleotidesleaves the nucleus; a ribosome reads itXa short strand folded into an Lcarries one amino acid at its 3′ endYa short strand paired to a DNA strandgives DNA polymerase a free 3′ end at a forkZlong strands folded up with proteinsbinds an mRNA and joins amino acids
Four RNAs from one cell, described.

The table describes four RNAs found in one eukaryotic cell.

Which row describes ribosomal RNA (rRNA)?

Question 5
A table with four columns, RNA, nucleotides 12 to 16 written 5′ to 3′, nucleotides 31 to 35 written 3′ to 5′, share of RNA molecules bound to the small molecule, and three rowsRNAnucleotides 12–16 (5′→3′)nucleotides 31–35 (3′→5′)boundas foundGCAUGCGUAC84 %change 1GCUUGCGUAC13 %change 2GCUUGCGAAC80 %
Three versions of one RNA and the share of each that bound the small molecule.

An RNA binds a small molecule only when it is folded. In the folded RNA, nucleotides 12–16 lie against nucleotides 31–35, the two stretches lying the opposite way round. A scientist made two changed versions of the RNA and measured the share of molecules that bound the small molecule. The table shows the results.

Which conclusion do the results support?

Question 6

Genes P and Q sit side by side on one chromosome. A short stretch of DNA is deleted just before gene P. Afterward, RNA polymerase makes no RNA from gene P and still makes RNA from gene Q.

Which stretch was deleted?

Question 7
A table with six columns, tube, a gene with its promoter, RNA nucleotides, RNA polymerase, extra, new RNA made, and four rowstubegene + promoternucleotidesenzymeaddedRNA made?1yesRNARNA polymerasenothingyes2yesDNARNA polymerasenothingno3yesRNARNA polymeraseprimer + helicaseyes4yesRNADNA polymerasenothingno
What each tube held, and whether new RNA appeared.

Four test tubes each hold a gene with its promoter and the enzyme and nucleotides listed in the table. The last column shows whether new RNA appeared.

Which statement do the four tubes support?

Question 8
Three monospace rows with a note beside each: 5′-CATGGTCAA-3′, strand X; 5′-TTGACCATG-3′, strand Y; 5′-UUGACCAUG-3′, the RNA5′-CATGGTCAA-3′strand X5′-TTGACCATG-3′strand Y5′-UUGACCAUG-3′the RNA
The two DNA strands of the stretch and the RNA made from it, each written from its own 5′ end.

The two DNA strands of a short stretch of a gene, X and Y, and the RNA made from that stretch are shown.

Which strand did RNA polymerase read as the template, and how do the sequences show it?

Question 9

RNA polymerase is part-way along a gene, with a growing RNA behind it.

Which statement describes the ends at that moment?

Question 10
One monospace row: 3′-ACG TTA GCC-5′3′-ACG TTA GCC-5′
The template strand, written from its 3′ end.

A template strand reads 3′-ACG TTA GCC-5′, as drawn.

Written with both ends marked, what does the RNA read?

Question 11
A horizontal line with five large ovals along it, each trailing a thin strand down and to the right; the strands differ in length
One gene with five RNA polymerases along it, each trailing its RNA.

One gene is drawn with five RNA polymerases along it at once. Each trails the RNA it has made so far.

At which end of the gene is the promoter?

Question 12
One monospace row: 5′-GCTACA-3′5′-GCTACA-3′
The non-template strand, written from its 5′ end.

A gene's non-template strand reads 5′-GCTACA-3′, as drawn.

Written with both ends marked, what does the RNA read?

Question 13

In a eukaryotic cell, enzymes in the nucleus add two things to a pre-mRNA before it leaves.

Which of the following do the enzymes join to the pre-mRNA's 3′ end?

Question 14
A table with three columns, mRNA, protein made in the first ten minutes, time until the mRNA is gone, and four rows lettered W, X, Y, ZmRNAprotein in the first 10 minmRNA gone afterWa lotmany hoursXa lotunder an hourYalmost nonemany hoursZalmost noneunder an hour
Four mRNAs put into cells: what happened to each.

Four copies of one gene's mRNA are made in a test tube. Each copy has or lacks a 5′ cap, and each copy has or lacks a poly-A tail. Each copy is put into a eukaryotic cell. The table shows how much protein each cell made in the first ten minutes and how long each mRNA lasted.

Which row is the mRNA with a 5′ cap and no poly-A tail?

Question 15

In a eukaryotic cell, a gene's pre-mRNA is 3,200 nucleotides long. Its mature mRNA has a coding length of 3,200 nucleotides.

Which statement about this gene is correct?

Question 16
Three rows: a gene drawn as a line with an open box, a bent arrow and four numbered filled boxes; beneath it a light row of the same four boxes joined by thin lines; beneath that a light row of the four boxes touching, with a dot at one end and a row of small tabs at the other. Four small circles carry the letters J, K, L and M, each with a leader to a part123412345′3′1234AAAAAAA…A5′3′JMKL
A gene, the RNA as released and the mature mRNA, with four parts lettered.

The drawing shows a eukaryotic gene with RNA polymerase on it, the RNA as released, and the mature mRNA. Four parts are lettered.

Which lettered part is a stretch that enzymes cut out before the mRNA leaves the nucleus?

Question 17
A table with three columns, mRNA, 5′ cap, poly-A tail, and four rows lettered W, X, Y, ZmRNA5′ cappoly-A tailWyesyesXyesnoYnonoZnoyes
Four mRNAs: what each carries.

The table describes four mRNAs.

Which mRNA was made by a bacterium?

How to tackle the free-response questions. Read the verb first: describe asks what you see or know; explain asks why or how, so name the mechanism; predict asks what will happen and why; justify asks for the evidence that supports a claim. Each point is earned by one idea, stated in a sentence that names the thing and the mechanism. Extra words earn nothing; a wrong extra can lose the point. If there is a figure or table, use what it shows. When you finish, check the box for each point your answer earns and compare your sentences with the full-credit answer.
Free response 1 · Analyze Data · 4 points
A eukaryotic gene is drawn as a gene map with every exon and intron length written on it, in nucleotides. Beneath it are the first nine bases of the template strand. A liver cell and a kidney cell each transcribe this gene. The liver cell's mature mRNA keeps every exon. The kidney cell's mature mRNA has a coding length of 765 nucleotides.
A gene map with the exon lengths written above the filled boxes and the intron lengths written below the line between them, the promoter labeled; beneath it one monospace row of nine DNA bases with its ends marked 3′ at the left and 5′ at the right127056021957303495promoter3′-GTC CAA TGC-5′the first nine bases of the template strand
The gene map with its lengths, and the first nine bases of the template strand.

(a) Identify the RNA that RNA polymerase makes from the nine template bases drawn, written with both ends marked. (1 point)

A full-credit answer: Under each template base its RNA partner: G gives C, T gives A, C gives G, C gives G, A gives U, A gives U, T gives A, G gives C, C gives G.
The RNA's 5′ end sits under the template's 3′ end.
So the RNA reads 5′-CAG GUU ACG-3′.

Check the box for each point your answer earns

Accept the same nine letters without the spaces.

Common slip: Writing 5′-GUC CAA UGC-3′: the template's own letters with U for T, not their partners.

(b) Calculate the coding length of the liver cell's mature mRNA. (1 point)

nucleotides

Write down the values on the map:

exon lengths=270,195,495

Coding length, in nucleotides, = sum of the exon lengths:

270+195+495=960

A full-credit answer: The liver cell kept every exon, so its coding length is the exon total.
270 + 195 + 495 = 960 nucleotides.

(c) Determine which exon the kidney cell's enzymes skipped. Justify your answer with the lengths. (1 point)

A full-credit answer: The kidney cell's mature mRNA is 765 nucleotides, 195 short of the full coding length of 960.
Exon 2 is 195 nucleotides long, and no other exon is.
So the kidney cell skipped exon 2.

Check the box for each point your answer earns

Accept consistent working from an incorrect (b) total: the exon whose length equals the student's own (b) total minus 765, with that subtraction shown.

Common slip: Subtracting an intron length. Introns are cut out in both cells; only exon lengths decide the coding length.

(d) Explain why the two cells' pre-mRNAs are the same length although the two mature mRNAs differ. (1 point)

A full-credit answer: RNA polymerase copies the whole gene, exons and introns, into the pre-mRNA in both cells.
So both pre-mRNAs are the full length of the gene, 2,250 nucleotides.
The two mRNAs differ only afterward, when the kidney cell's enzymes cut out exon 2 along with the introns.

Check the box for each point your answer earns

Common slip: Saying the kidney cell's gene is shorter. The DNA is the same in both cells; splicing, not the gene, differs.

Free-response score: 0 of 4
Free response 2 · Conceptual Analysis · 4 points
A gene in a plant's leaf cells has four exons. In leaf cells in the light, the mature mRNA from this gene carries exons 1, 2, 3 and 4. In the same leaf cells in the dark, the mature mRNA carries exons 1, 2 and 4. The two mature mRNAs are drawn.
Two light rows of numbered boxes touching end to end, each with a dot at its left end and a row of small tabs lettered A at its right end and 5′ and 3′ written at the ends; the upper row is named leaf cell in the light and has four boxes, the lower is named leaf cell in the dark and has threeleaf cell in the light1234AAAAAAA…A5′3′leaf cell in the dark124AAAAAAA…A5′3′
The gene's mature mRNA in a leaf cell in the light and in the dark.

(a) Describe how the leaf cell's enzymes treat the pre-mRNA of this gene differently in the light and in the dark. (1 point)

A full-credit answer: In the light the enzymes cut out only the introns and join all four exons.
In the dark the enzymes cut out exon 3 along with the introns beside it and join exons 1, 2 and 4.

Check the box for each point your answer earns

(b) Explain why the protein made in the dark is related to the protein made in the light but differs from it. (1 point)

A full-credit answer: Ribosomes read each mature mRNA into a protein.
Both mRNAs carry exons 1, 2 and 4, so both proteins share the parts made from those exons.
The dark mRNA lacks exon 3, so the dark protein lacks the part made from exon 3.

Check the box for each point your answer earns

Common slip: Saying the dark protein is unrelated. Three of the four exons are shared, so most of the protein is the same.

(c) Predict what a comparison of this gene's DNA in a leaf cell in the light and a leaf cell in the dark would show. (1 point)

A full-credit answer: The gene's DNA is the same in both cells: the same exons and the same introns, in the same order.

Check the box for each point your answer earns

Common slip: Predicting that exon 3 is missing from the gene in the dark. The exon is missing from the mRNA, not from the DNA.

(d) Justify your prediction. (1 point)

A full-credit answer: Splicing changes which stretches of the RNA copy are kept.
Enzymes cut exon 3 out of the pre-mRNA, not out of the gene.
So the gene's DNA keeps exon 3 in the dark as in the light, and the same gene gives two different mRNAs.

Check the box for each point your answer earns

Free-response score: 0 of 4
Feedback and scoring guides appear after you submit.
Multiple choice checked: 0 of 17 correct.
Next: Where proteins are built