Biology • Year 12 • Module 6 • Lesson 16

Recombinant DNA Technology and Transgenic Organisms

Lock in the toolchain (cut → join → carry → insert → use), the distinction between transgenic and selectively bred organisms, and the role of each enzyme and vector.

Build · Toolchain & Vocab

1. Label the recombinant DNA process flowchart

The flowchart below sequences the recombinant DNA technology toolchain from this lesson. Write the missing labels into boxes A–H. Labels are drawn from the lesson's Key Terms or from Cards 1–2. 8 marks

Diagram coming soon
  1. A — enzyme that cuts donor DNA at a specific sequence _______________________
  2. B — characteristic overhanging single-stranded ends produced _______________________
  3. C — enzyme that seals the donor fragment into the opened vector _______________________
  4. D — name for the combined fragment + vector structure _______________________
  5. E — cell type that receives the recombinant vector _______________________
  6. F — outcome 1 (the inserted gene is …) _______________________
  7. G — outcome 2 (the inserted gene is …) _______________________
  8. H — name for a whole organism carrying inserted DNA _______________________
BoxYour label
A
B
C
D
E
F
G
H
Stuck? Revisit lesson § Card 1 (toolchain spine) and Card 2 (four-step process tiles).

2. Term–definition match

The ten definitions below are shuffled. In the right-hand column write the matching term from this list: recombinant DNA, restriction enzyme, DNA ligase, vector, plasmid, host cell, transgenic organism, sticky ends, selective breeding, recognition sequence. 10 marks

#Definition (shuffled)Matching term
2.1DNA formed by combining genetic material from different sources.
2.2An enzyme that cuts DNA at specific base sequences.
2.3An enzyme that joins DNA fragments together.
2.4A carrier (e.g. a plasmid) used to move DNA into a host cell.
2.5A small circular DNA molecule found in bacteria and commonly used as a vector.
2.6The cell that receives recombinant DNA and can replicate or express it.
2.7An organism that contains inserted DNA from another source.
2.8Short complementary single-stranded overhangs produced by some restriction enzymes that base-pair with matching fragments.
2.9The reproductive method of choosing parents with existing traits and allowing offspring to inherit reshuffled alleles.
2.10The specific short DNA sequence at which a restriction enzyme cuts.
Stuck? Revisit lesson § Key Terms panel and the misconceptions box at the top of Card 1.

3. True or false — with correction

For each statement, circle T or F. If the statement is false, write the corrected version. 8 marks (1 for T/F, 1 for the correction where needed)

3.1 A transgenic organism is just a cross-bred organism with carefully chosen parents.    T  /  F

3.2 DNA ligase cuts DNA at specific recognition sites.    T  /  F

3.3 For a donor fragment to be ligated into a vector, both should normally be cut with the same restriction enzyme so their sticky ends are complementary.    T  /  F

3.4 A host cell is needed because recombinant DNA cannot be replicated or expressed unless it is inside a living cell.    T  /  F

Stuck? Revisit lesson § Misconceptions box, Card 2 (process tiles), Card 3 (transgenic vs bred).

4. Function recall

Answer each in 1–2 sentences using precise terms from the lesson. 10 marks (2 each)

4.1 What is the function of a restriction enzyme in recombinant DNA technology?

4.2 What is the function of DNA ligase?

4.3 What is the function of a vector (e.g. a plasmid)?

4.4 What is the function of a host cell?

4.5 What is the function of the recognition sequence at the start of the toolchain?

Stuck? Revisit lesson § Cards 1–2 and Key Terms panel.

5. Sticky-end DNA sequence task

Restriction enzyme EcoRI recognises the sequence GAATTC on double-stranded DNA and cuts between the G and the first A on each strand, leaving 4-base single-stranded overhangs ("sticky ends"). The double-stranded donor DNA fragment below contains one EcoRI recognition site. 6 marks

5'- C A T G G A A T T C G C T A T -3'
3'- G T A C C T T A A G C G A T A -5'

5.1 Circle or underline the recognition sequence on the strand above. Identify the exact base pair between which EcoRI cuts on each strand. 2 marks

5.2 Write out the two resulting fragments after EcoRI cuts, showing the 4-base single-stranded "sticky end" overhangs on each. Use the same monospace layout. 2 marks

Left fragment:
5'- _ _ _ _ _ _ _ _ _ _ _ _ _ -3'
3'- _ _ _ _ _ _ _ _ _ _ _ _ _ -5'

Right fragment:
5'- _ _ _ _ _ _ _ _ _ _ _ _ _ -3'
3'- _ _ _ _ _ _ _ _ _ _ _ _ _ -5'

5.3 A plasmid vector has also been cut with EcoRI. Explain in one sentence why this matters for joining the donor fragment into the plasmid, naming the enzyme that performs the final join. 2 marks

Stuck? Revisit § Misconceptions box (same enzyme → complementary sticky ends) and § Card 2 (ligase joins).

6. Build a concept map

Draw labelled arrows between the six terms below to show how they connect across the toolchain. Each arrow must carry a linking phrase (e.g. "cuts", "joins", "carries", "produces"). Aim for at least 6 labelled arrows. 5 marks

Supplied terms: restriction enzyme · DNA ligase · vector (plasmid) · recombinant DNA · host cell · transgenic organism.

restriction enzyme
DNA ligase
vector (plasmid)
recombinant DNA
host cell
transgenic organism
Stuck? Think about the chain: enzyme cuts → ligase joins fragment into vector → recombinant DNA → host cell → (in a multicellular organism) transgenic organism.
Answers — Do not peek before attempting

Q1 — Labelled flowchart

A: restriction enzyme. B: sticky ends (complementary single-stranded overhangs). C: DNA ligase. D: recombinant DNA (the donor fragment ligated into the vector / a recombinant plasmid). E: host cell (e.g. a bacterial cell). F: replicated / copied (the inserted DNA is copied as the host cell divides). G: expressed (the inserted gene is transcribed and translated to produce a protein). H: transgenic organism.

Q2 — Term–definition matches

2.1 recombinant DNA • 2.2 restriction enzyme • 2.3 DNA ligase • 2.4 vector • 2.5 plasmid • 2.6 host cell • 2.7 transgenic organism • 2.8 sticky ends • 2.9 selective breeding • 2.10 recognition sequence.

Q3 — True / false with correction

3.1 False. Correction: a transgenic organism contains DNA inserted from another source using recombinant DNA techniques; it is not produced by ordinary selective breeding, which only reshuffles existing alleles between parents.

3.2 False. Correction: DNA ligase joins DNA fragments together; cutting at recognition sites is done by restriction enzymes.

3.3 True.

3.4 True. (Accept partial credit: cells provide the replication / transcription / translation machinery needed to copy or express the DNA.)

Q4.1 — Function of a restriction enzyme

A restriction enzyme cuts double-stranded DNA at a specific recognition sequence. This isolates the gene of interest from donor DNA and, when used on the vector, opens the vector at a matching site so the donor fragment can be inserted.

Q4.2 — Function of DNA ligase

DNA ligase joins the donor DNA fragment to the opened vector by sealing the sugar–phosphate backbone, producing one continuous recombinant DNA molecule. Without ligase the cut fragments would only base-pair temporarily via their sticky ends.

Q4.3 — Function of a vector (e.g. a plasmid)

A vector carries the inserted DNA into the host cell. Plasmids in particular can also be replicated by the host's machinery, so each host cell produces many copies of the recombinant DNA.

Q4.4 — Function of a host cell

The host cell receives the recombinant vector and provides the molecular machinery (e.g. DNA polymerase, ribosomes) needed either to copy the inserted DNA as the cell divides, or to express it as a functional protein.

Q4.5 — Function of the recognition sequence

The recognition sequence is the specific short DNA sequence that a restriction enzyme binds and cuts. It ensures the enzyme cuts at predictable positions on both donor DNA and vector, so the resulting fragments have compatible (complementary) sticky ends that can be ligated together.

Q5 — Sticky-end DNA sequence task

5.1 (2 marks). Recognition sequence is GAATTC (5'→3' on the top strand, positions 5–10). EcoRI cuts between G and A on each strand — i.e. after the G on the top strand and after the G on the bottom strand (5'-G↓AATTC-3' / 3'-CTTAA↓G-5').

5.2 (2 marks). The two resulting fragments, each with a 4-base 5' overhang (sticky end):

Left fragment:
5'- C A T G G             -3'
3'- G T A C C T T A A     -5'

Right fragment:
5'-         A A T T C G C T A T -3'
3'-               G C G A T A   -5'

Each fragment has the 4-base overhang AATT exposed (one as 5' overhang on the top strand, the other as 5' overhang on the bottom strand). These overhangs are complementary and base-pair when fragments are brought together.

5.3 (2 marks). Because the plasmid was cut with the same enzyme (EcoRI), it has the same 4-base sticky end (AATT), which is complementary to the donor fragment's sticky end [1]. The two overhangs base-pair, and DNA ligase then seals the sugar–phosphate backbone, producing recombinant DNA [1].

Q6 — Sample concept map

A correct map should include arrows such as:

  • restriction enzyme — cuts both donor DNA and → vector (plasmid)
  • restriction enzyme — produces sticky ends used by → DNA ligase
  • DNA ligase — seals donor fragment into vector to make → recombinant DNA
  • vector (plasmid) — carries → recombinant DNA into → host cell
  • host cell — replicates or expresses → recombinant DNA
  • host cell (inside an organism receiving the inserted DNA) — contributes to development of → transgenic organism

Any biologically valid linking phrases are accepted. Award full marks for at least 6 correctly labelled arrows that respect causal direction.

HSCScience • Biology • Year 12 • Module 6 • Lesson 16 • Worksheet 1 (Build)