DNA Structure & Replication — Print · Grade 10 Science
Chapter: DNA, Inheritance & Gene ExpressionDNA Structure & Replication
Learning goals
- I can describe the structure of DNA, including the double helix and complementary base pairing (A-T, C-G).
- I can explain how semiconservative replication copies DNA so each new molecule keeps one original strand and one new strand.
Readings for this unit
Before this unit
Pair complementary bases and distinguish strands from chromosomes.
Use three flexible study sessions: core explanation and Parts 1–2; Parts 3–4 with their reasoning checks and models; then the whole-unit application, worked examples, independent practice, and exit check. Allow about 50–60 minutes per session, including diagrams, data work, and notebook explanations. Attempt each check before opening its guidance. Schedule chapter investigations, review, and exams separately; add time where prerequisites are uncertain. Trace the explained visual parts and write a first model, then attempt the illustrated and changed independent cases. In the third session explain a correction and revise the opening account using evidence.
Start with something to explain
How can DNA be copied without losing the old template information?
Illustrative evidence case. Complementary, antiparallel strands serve as templates for new partners; correction limits but does not eliminate errors.
Notice and wonder
Record two observations using the stated quantities or relationships. Keep observations separate from possible causes. Write one question that a new measurement could help answer.
How can DNA be copied without losing the old template information?
Your first model
Label base pairing, backbone direction and old/new strand origin.
Build the language from the idea
- nucleotide
- The building block of DNA, made of a sugar, a phosphate group, and one of four nitrogen bases (A, T, C, or G).
- double helix
- The twisted-ladder shape of a DNA molecule, formed by two strands winding around each other.
- complementary base pairing
- The rule that adenine always pairs with thymine (A-T) and cytosine always pairs with guanine (C-G).
- semiconservative replication
- The way DNA copies itself so that each new double helix keeps one original strand and one newly built strand.
- DNA polymerase
- The enzyme that builds a new DNA strand by adding matching nucleotides one at a time along a template strand.
- antiparallel
- The two paired DNA backbones run in opposite 5′/3′ chemical directions.
- semiconservative
- Each copied duplex retains an original strand and gains a new complementary strand in the standard model.
Inside almost every one of your cells sits a molecule with a nearly impossible job: storing the complete instructions for building and running a human being, written in a code so compact that the DNA from a single cell would stretch about two meters if you unwound it, yet folds up small enough to vanish inside a nucleus. The secret to that density — and to nearly everything DNA does — is its elegant structure. DNA is built from small repeating units called nucleotides, each one a set of three parts: a sugar, a phosphate group, and one of just four nitrogen bases, abbreviated A, T, C, and G.
Link many nucleotides together and you get a single strand; bring two strands together and they twist into DNA's famous double helix — the shape of a ladder gently spiraled around its own length. The two outer rails of that ladder are an alternating sugar-and-phosphate backbone, sturdy and repetitive, while the rungs are where the information actually lives. Each rung is a pair of bases reaching toward each other from opposite strands, and here is the crucial rule: the pairing is never random. Adenine always bonds with thymine (A-T), and cytosine always bonds with guanine (C-G) — a principle called complementary base pairing.
That one rule turns out to be the key to the whole molecule. Because A only fits T and C only fits G, the two strands are not identical but *complementary* — each is a kind of mirror image of the other. If you know the sequence of one strand, you automatically know the sequence of its partner: read one strand as A-T-G-C and its partner must read T-A-C-G. In effect, nature stores every gene twice over in matched form, and that built-in redundancy is exactly what makes DNA so easy to copy without losing information.
Copying happens every time a cell prepares to divide, in a process called semiconservative replication. First the double helix unzips down the middle, breaking the weak bonds between the paired bases and separating the two strands like a zipper. Each exposed strand then serves as a template: an enzyme called DNA polymerase moves along it and adds free-floating nucleotides one by one, always obeying the pairing rule — slotting a T opposite every A, a G opposite every C. By the time it finishes, each old strand has a brand-new partner strand built alongside it.
The result is two complete double helices where there was one, and each of them is half old and half new: one original strand conserved, one freshly assembled. (That 'half-conserved' detail is why the process is called *semi*conservative, and a famous 1958 experiment confirmed it.) Copying this way is astonishingly accurate — DNA polymerase even proofreads its own work, catching most mistakes as it goes. But 'most' is not 'all,' and a rare uncorrected error — a wrong base slipped into the sequence — is one important source of the mutations that ultimately make every organism genetically unique.
DNA's complementary base pairing supports copying: each original strand can guide synthesis of a new complementary strand. The process is semiconservative in the standard model, leaving each new double helix with one old and one new strand.
Replication accuracy depends on enzymes, proofreading and repair. A copying error that escapes correction can become a mutation, but not every DNA damage event becomes a permanent inherited change. Distinguish a temporary lesion from a stable sequence change.
A chromosome contains a long DNA molecule with associated proteins and many functional regions. A gene is not an entire chromosome, and not all DNA codes for protein. Use scale and organization clearly when moving between bases, genes and chromosomes.
Build your understanding
Use three flexible study sessions: core explanation and Parts 1–2; Parts 3–4 with their reasoning checks and models; then the whole-unit application, worked examples, independent practice, and exit check. Allow about 50–60 minutes per session, including diagrams, data work, and notebook explanations. Attempt each check before opening its guidance. Schedule chapter investigations, review, and exams separately; add time where prerequisites are uncertain.
Part 1 · A ladder with a rule
A DNA nucleotide includes a sugar, phosphate and base. Complementary pairing links A with T and G with C in the ordinary DNA model. Antiparallel means the backbones run in opposite chemical directions, labeled 5′ and 3′ according to sugar positions, not page coordinates. Hydrogen bonds between bases differ from covalent backbone connections. A flattened ladder makes pairing readable but does not show the full helical geometry or molecular flexibility. Sequence direction must be preserved when constructing or comparing complements.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
What is the paired sequence beneath 5′-ATGCAT-3′ when written directly opposite?
Visual reasoning — after your attempt
3′-TACGTA-5′, antiparallel to the supplied strand.
DNA is a polymer of nucleotides, each made of a sugar, a phosphate group, and one of four nitrogenous bases: adenine, thymine, guanine, cytosine. The sugar and phosphate units link into a backbone, and the bases project inward. Two such strands wind around each other, held together by hydrogen bonds between paired bases, with the two backbones running in opposite directions.
The pairing is specific: adenine with thymine, guanine with cytosine. That single rule explains the structure's most important property. Because each base admits only one partner, either strand specifies the other completely, so the molecule carries a built-in template for its own reconstruction. The information is in the sequence of bases; the backbone is identical all the way along.
Pause and explain
Why does the sequence of bases carry the information rather than the sugar-phosphate backbone?
Check your reasoning after answering
The backbone is the same repeating unit along the whole strand, so it cannot distinguish one region from another. Only the order of the four bases varies, so only that order can encode anything.
Part 2 · The evidence behind the model
A structural model proposes how components are arranged. Chemical composition, base ratios and diffraction patterns helped constrain DNA’s double-helical explanation; an image pattern is not itself a direct photograph of every base. Independent evidence checks different predictions, such as pairing and backbone organization. Credit the observations and model-building contributions rather than treating a memorable sketch as discovery by one person alone. A good model can be revised in detail while retaining relationships supported by multiple tests.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
Why is a drawing of a helix not by itself proof of DNA structure?
Visual reasoning — after your attempt
A drawing is a proposal; chemical and structural measurements must support its predictions and rule out alternatives.
The double helix was inferred rather than seen. X-ray diffraction images, principally those produced by Rosalind Franklin and Raymond Gosling, indicated a helical molecule with a regular repeat and a measurable diameter — too uniform to be a structure with variably sized pairs on the inside. Separately, Erwin Chargaff's measurements showed that in a given species the amount of adenine equals that of thymine and guanine equals cytosine.
Watson and Crick's model accounted for both results at once: a large base paired with a small one in each rung keeps the diameter constant, and specific A-T and G-C pairing produces exactly Chargaff's equalities. This is a clear case of a model being accepted because it explained several independent measurements, not because the structure had been observed directly.
Pause and explain
Why would pairing adenine with guanine be inconsistent with the diffraction evidence?
Check your reasoning after answering
Both are large bases, so such a rung would be wider than one pairing a large base with a small one. The images showed a constant diameter, which requires every rung to be the same width — one large base with one small one.
Part 3 · Semiconservative replication
Semiconservative replication produces two duplexes, each with an original template strand and a newly synthesized partner in the basic model. Strand separation exposes templates, and pairing constrains new sequence. DNA polymerase builds in the 5′→3′ direction, with additional enzymes and mechanisms supporting copying and ligation. Replication is not splitting each base in half or preserving an entirely old double helix beside an entirely new one. One old strand per product is the central inheritance pattern; actual forks involve more detailed leading/lagging behavior.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
After one ideal round, does either product contain two entirely old strands?
Visual reasoning — after your attempt
No. Each has one old and one new strand under the semiconservative model.
Replication begins with the two strands separating. Each then serves as a template: free nucleotides pair with the exposed bases, and an enzyme joins them into a continuous new strand. The result is two double helices, each containing one original strand and one newly made one — which is what semiconservative means.
The phrase matters because two alternatives were plausible before the experiments. Replication might have produced one entirely original molecule and one entirely new one, or might have broken and recombined the strands throughout. Labelling the original strands with a heavier isotope and following them into the products distinguished the possibilities, and the observed pattern matched the semiconservative prediction.
Pause and explain
After one round of replication, how many of the four strands present are original, and in which molecules?
Check your reasoning after answering
Two of the four are original, and they are in different molecules — one in each product. Each double helix therefore has one original and one new strand, which is the semiconservative outcome.
Part 4 · Accuracy, errors, and why both matter
A mismatch is an inappropriate pairing in a copying event; a lasting mutation is a sequence change retained after the relevant processes. Proofreading and repair reduce errors, but no simplified model guarantees every sequence is copied perfectly. A percentage of mismatches among copied bases differs from the number of cells carrying a mutation or its phenotypic effect. Specify the denominator, correction stage and sampling method. Mutation effects depend on location, gene regulation, protein changes and environment rather than a universal beneficial/harmful label.
Read the visual model
Identify the labeled structures and units, then trace the arrows or compare values under the caption’s stated conditions. Separate the displayed evidence from a further inference. Write your reasoning before opening the guidance.
Do ten initial mismatches necessarily establish ten permanent trait changes?
Visual reasoning — after your attempt
No. Repair, inheritance, location and expression affect whether an error persists and changes a measured trait.
Replication is extremely accurate but not perfect. Incorrect bases are occasionally inserted, and repair mechanisms detect and correct most of them; those that remain are mutations. Because replication precedes every cell division, an uncorrected error in a dividing cell is passed to all its descendants, which is why checkpoint control and repair matter so much.
Both the accuracy and the residual error rate are biologically necessary. High accuracy keeps genetic information stable across generations of cells and organisms; the small error rate is one source of the heritable variation on which natural selection acts. Describing mutation as simply damage misses the second half of that account.
Pause and explain
Why is a replication error in a cell that will divide many times more consequential than one in a cell that will not divide again?
Check your reasoning after answering
Every descendant of a dividing cell inherits the error, so a single mistake can be multiplied into a large population of altered cells. In a cell that will not divide, the error affects only that cell.
Apply the whole unit · Reconstruct a strand and audit a composition
Illustrative data for a double-stranded DNA sample. Measured composition: cytosine 22 percent. A fragment of one strand reads 5'-TTACGGCAT-3'. The sample is reported to have replicated twice in a labelling experiment that marked the original strands.
Your task
Calculate the percentages of guanine, adenine, and thymine and state the rule each step uses, write the complementary sequence for the fragment, and determine how many of the strands present after two rounds of replication are original. Then explain what result would have shown that replication is not semiconservative.
What your response should show
- Choose the appropriate biological model or relationship and state the conditions it assumes.
- Show the counts, rates, ratios, or intermediate reasoning the question requires.
- Use the supplied evidence to justify the conclusion and separate observation from inference.
- Identify a meaningful limitation, uncertainty, or next measurement.
Response guidance — after your attempt
Guanine: G pairs with C, so G = 22 percent.
Remaining: C and G together are 44 percent, so A and T together are 100 − 44 = 56 percent.
Adenine and thymine: A pairs with T, so each is 56 / 2 = 28 percent.
Complement of 5'-TTACGGCAT-3': pair each base, giving 3'-AATGCCGTA-5', which read in the standard direction is 5'-ATGCCGTAA-3'.
Strands after two rounds: one molecule becomes four, so 8 strands exist; only the 2 original strands are old, and they lie in two different molecules.
A non-semiconservative result: finding molecules made of two original strands alongside molecules of two new strands after one round would indicate conservative replication, while finding every strand to be a patchwork of old and new segments would indicate dispersive replication.
With cytosine at 22 percent, guanine is also 22 percent because the two pair, leaving 56 percent to be divided equally between adenine and thymine at 28 percent each. The complement of 5'-TTACGGCAT-3' is 5'-ATGCCGTAA-3', obtained by pairing each base and reading the new strand in the opposite orientation, since the two backbones run in opposite directions. After two rounds of replication the original molecule has become four, so eight strands exist, of which only the two originals are old and they sit in separate molecules — each of the other two molecules is entirely new. The semiconservative claim would have been refuted by either of two outcomes: molecules of two original strands appearing alongside wholly new molecules after one round, which is conservative replication, or every strand turning out to be a mixture of old and new segments, which is dispersive replication. The labelling experiment matters precisely because the structure alone does not decide between these.
Scientific references and adapted source figures
Parent / teacher teaching notes
The Chargaff arithmetic is the quickest reliable check on whether base pairing has been understood, and it is worth repeating with several starting percentages until it is automatic. Insist on the complement being written with its direction, since reading a strand backwards is the usual source of wrong answers. The semiconservative point rewards a minute of attention to the alternatives: students who can state what conservative and dispersive replication would have looked like understand why an experiment was needed at all. Ask for an explanation of each label, arrow and axis before calculation. Keep first and revised models; attempt the changed case before consulting guidance. Distinguish invented instructional records from named historical sources. Source chromosome symbols are allele-category models, not DNA sequences. These independently authored high-school supplements are not the full OpenSciEd teacher editions or an endorsement.
A rotating double-helix model of DNA showing its twisted-ladder shape, with paired bases forming the rungs.
The key idea
DNA is a double helix of nucleotides whose bases pair by a strict rule (A-T, C-G); this complementary pairing lets DNA copy itself semiconservatively, so each new molecule keeps one original strand and one new one.
Chargaff's Rules
%A = %T, %G = %C, and A + T + G + C = 100%
any sample of double-stranded DNA, because the bases pair A-T and C-G.
Worked examples
Example 1
- Apply the pairing rule to each base: A pairs with T, and C pairs with G (and the reverse).
- Go base by base: A to T, T to A, G to C, C to G, C to G, G to C, T to A, A to T.
- Read the new bases off in the same order.
Example 2 · Worked application
- Use A–T and C–G pairing: TGCA.
- Replication separates parental strands and makes a new complement for each.
- Each daughter double helix contains one old and one new strand.
Pairing rules provide a template mechanism; sequence order still matters.
Example 3
- Because A always pairs with T, the amount of thymine equals the amount of adenine: T = 30%.
- Together, A and T make up 30% + 30% = 60% of the bases, leaving 40% for C and G combined.
- Because C always pairs with G, that 40% splits evenly between them: G = 20% (and C = 20%).
Example 4
- A pairs with T and C with G.
- Apply the rule to each position in the supplied order.
Example 5 · Find and fix the mistake
- Test the claim against the stated conditions: Pairing rules provide a template mechanism; sequence order still matters.
- Semiconservative replication retains one parental strand in each daughter double helix.
Pairing rules provide a template mechanism; sequence order still matters.
Example 6 · Reason from the visual evidence
- Semiconservative replication produces two duplexes, each with an original template strand and a newly synthesized partner in the basic model. Strand separation exposes templates, and pairing constrains new sequence. DNA polymerase builds in the 5′→3′ direction, with additional enzymes and mechanisms supporting copying and ligation. Replication is not splitting each base in half or preserving an entirely old double helix beside an entirely new one. One old strand per product is the central inheritance pattern; actual forks involve more detailed leading/lagging behavior.
- No. Each has one old and one new strand under the semiconservative model.
Original strand-origin and pairing comparison. Colors identify strand history, not different base chemicals or all replication-fork proteins.
Avoid these mistakes
- DNA replication does not make a second strand identical to its complementary partner.
Check your understanding
An original DNA strand has bases A-C-G-T. Give its complementary sequence and explain the pairing rule.
Discuss the answer
T-G-C-A in corresponding paired positions; actual strands have opposite orientation.
What does semiconservative replication preserve in each daughter DNA molecule?
Discuss the answer
Each copied duplex retains an original template strand and gains a complementary newly synthesized partner in the standard semiconservative model.
Return to the phenomenon
Return to the initial case. How can DNA be copied without losing the old template information? Revise your drawing or explanation using two named ideas and one stated limitation.
Compare explanations after your attempt
Semiconservative copying preserves an old strand in each duplex; sequence direction and repair stages matter for the inheritance account.
What should we investigate next?
Which comparison would test a remaining uncertainty? State what you would change, keep comparable and measure.
Investigate, explain and revise
Complete these tasks after the teaching parts. Preserve your first model and a supported revision; use guidance after a real attempt.
Activity 1 · Return to the opening case
Use the opening question, defined terms, Parts 1–4 and your notebook. The supplied-data route needs no equipment or external account.
Your task
Return to the initial case. How can DNA be copied without losing the old template information? Revise your drawing or explanation using two named ideas and one stated limitation.
Success criteria
- Use relevant stated observations.
- Explain the mechanism with a labeled model.
- Distinguish quantities and assumptions.
- Describe a revision and a useful next test.
Hint
Follow objects, materials and information separately. Check what each measured quantity means.
Response guidance — discuss after your attempt
Semiconservative copying preserves an old strand in each duplex; sequence direction and repair stages matter for the inheritance account.
Activity 2 · Transfer to a changed case
Cover the worked guidance and use the unit explanations/figures to solve a changed problem.
Your task
Write the complementary strand opposite 5′-AACGTT-3′, then explain strand origin after one semiconservative round.
Success criteria
- Use the stated measurements or conditions, with correct units.
- Connect the result to the biological mechanism or evidence relationship.
- Identify the assumption, model limit or further evidence requested.
Hint
Name the stated conditions, select the relevant mechanism and show intermediate reasoning.
Response guidance — discuss after your attempt
The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.
Words to know
- nucleotide
- The building block of DNA, made of a sugar, a phosphate group, and one of four nitrogen bases (A, T, C, or G).
- double helix
- The twisted-ladder shape of a DNA molecule, formed by two strands winding around each other.
- complementary base pairing
- The rule that adenine always pairs with thymine (A-T) and cytosine always pairs with guanine (C-G).
- semiconservative replication
- The way DNA copies itself so that each new double helix keeps one original strand and one newly built strand.
- DNA polymerase
- The enzyme that builds a new DNA strand by adding matching nucleotides one at a time along a template strand.
- antiparallel
- The two paired DNA backbones run in opposite 5′/3′ chemical directions.
- semiconservative
- Each copied duplex retains an original strand and gains a new complementary strand in the standard model.
The experiment that proved 'semiconservative'
When Watson and Crick proposed the double helix in 1953, they noted it 'immediately suggests a possible copying mechanism' — but three competing ideas about how DNA copies remained. In 1958, Matthew Meselson and Franklin Stahl settled it: they grew bacteria in 'heavy' nitrogen, switched them to 'light' nitrogen, and measured the density of the DNA after each round of copying. After one round, every molecule was exactly intermediate — one heavy (old) strand and one light (new) strand — proving replication is semiconservative. It's often called 'the most beautiful experiment in biology.'
Rosalind Franklin and Photo 51
The famous double-helix model leaned heavily on an X-ray diffraction image known as Photo 51, produced using techniques perfected by Rosalind Franklin. Her crisp diffraction pattern revealed DNA's helical shape and dimensions. Franklin died of cancer in 1958, before the 1962 Nobel Prize honored the discovery; because Nobel Prizes are not awarded posthumously, her essential contribution went unrecognized by that award.
The strands run in opposite directions
The two strands of DNA are not only complementary, they are antiparallel — they run in opposite directions, one oriented 5' to 3' and the other 3' to 5'. This matters because DNA polymerase can only build a new strand in one direction. As a result, one new strand is made smoothly and continuously while the other has to be built in short, backward pieces that are later stitched together — a surprising complication hidden inside the tidy 'unzip and copy' picture.
Why chromosome ends need caps
Because of how replication works, the machinery can't quite finish copying the very tips of a chromosome, so a little is lost each time. To protect the important genes, chromosomes end in repetitive, non-coding caps called telomeres — like the plastic tips on shoelaces. Telomeres get slightly shorter with every division, and once they wear down too far, the cell stops dividing. This ties DNA structure directly to aging and to how cells 'count' their divisions.
One typo, enormous consequences
Not every mutation is a sweeping change — some of the most significant involve a single wrong letter out of billions. Sickle-cell disease results from one base change in the gene for hemoglobin, the oxygen-carrying protein in red blood cells. That single substitution makes the cells collapse into a rigid, sickle shape that can jam narrow blood vessels. It's a vivid reminder that because DNA is read so precisely, a change to even one nucleotide can ripple out to affect an entire body.
In the real world
The copy-from-a-template logic of DNA replication is the basis of PCR, the lab technique used to amplify tiny DNA samples for COVID-19 tests, forensic 'DNA fingerprinting' at crime scenes, and at-home ancestry kits.
Exit check
Why can either DNA strand serve as a copying template?
Check your explanation after answering
Complementary base-pairing rules specify the corresponding bases on a new strand; normal replication pairs one original strand with one newly made strand.
Explain your reasoning without notes. If a key idea is missing, revisit the lesson and try again.
Problem 1
- thymine (T)
- cytosine (C)
- guanine (G)
- another adenine (A)
Answer and explanation
thymine (T)
A-T and C-G are the complementary base pairs; adenine always bonds with thymine.
Problem 2
- A double helix — a twisted ladder
- A single straight line
- A flat triangle
- A solid sphere
Answer and explanation
A double helix — a twisted ladder
Two strands wind around each other to form the double-helix, or twisted-ladder, shape.
Problem 3
Answer and explanation
40 thymine bases
Adenine pairs only with thymine, so 40 A bases require 40 T partners.
Problem 4
Answer and explanation
Each new DNA molecule is made of one original (conserved) strand and one newly built strand, so half of every copy is 'old.' That is what 'semiconservative' means.
Problem 5
- Each strand acts as a template that determines exactly which bases must be added to build its partner
- The bases pair together completely at random
- Both strands are identical, so one can be thrown away
- DNA does not need to be copied before a cell divides
Answer and explanation
Each strand acts as a template that determines exactly which bases must be added to build its partner
Because A only pairs with T and C only with G, one strand's sequence dictates its partner's, so each old strand is a perfect template for building a new one.
Problem 6
Answer and explanation
T-G-C-A in corresponding paired positions; actual strands have opposite orientation.
A pairs with T and C with G.
Apply the rule to each position in the supplied order.
Response criteria
- Use the stated conditions.
- Show the evidence or calculation.
- Explain the conclusion and any stated limitation.
Problem 7
Hints
Pairing rules provide a template mechanism; sequence order still matters.
Answer and explanation
AACG, pairing T with A and G with C.
Problem 8
Hints
State what the supplied observations or conditions establish, and separate that from any assumption.
Answer and explanation
A sequence change can persist and be copied into later DNA molecules.
Problem 9
Answer and explanation
No. Each has one old and one new strand under the semiconservative model.
Semiconservative replication produces two duplexes, each with an original template strand and a newly synthesized partner in the basic model. Strand separation exposes templates, and pairing constrains new sequence. DNA polymerase builds in the 5′→3′ direction, with additional enzymes and mechanisms supporting copying and ligation. Replication is not splitting each base in half or preserving an entirely old double helix beside an entirely new one. One old strand per product is the central inheritance pattern; actual forks involve more detailed leading/lagging behavior.
No. Each has one old and one new strand under the semiconservative model.
Response criteria
- Read the structures, axes, directions and units correctly.
- Connect the evidence with the biological mechanism.
- Respect stated model assumptions and distinguish an observation from a further inference.
Problem 10
Answer and explanation
The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.
The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.
Response criteria
- Use the stated measurements or conditions, with correct units.
- Connect the result to the biological mechanism or evidence relationship.
- Identify the assumption, model limit or further evidence requested.