---
title: "Recombinant DNA and Gene Transfer"
description: "Restriction enzymes cut DNA at named sequences, ligase joins the pieces, and a vector carries the gene into a host cell. Marker genes are how the few successful cells get found."
canonical: https://lightmysky.com/learn/science/recombinant-dna-and-gene-transfer-mt_L9yncU_x2P
source: https://lightmysky.com/learn/science/recombinant-dna-and-gene-transfer-mt_L9yncU_x2P.md
retrieved: 2026-09-12
---

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# Recombinant DNA and Gene Transfer

Restriction enzymes cut DNA at named sequences, ligase joins the pieces, and a vector carries the gene into a host cell. Marker genes are how the few successful cells get found.

Subject: Science · Area: Genetics & Evolution · Ages 17 to 18
Page: https://lightmysky.com/learn/science/recombinant-dna-and-gene-transfer-mt_L9yncU_x2P

## Ready when they can

- Explains why sticky ends produced by the same restriction enzyme join.
- Orders the steps from isolating a gene to a host cell expressing it.
- Says what a marker gene is for and why most transformed cells fail.

## Lesson: Cutting pasting and delivering genes

Genetic engineers borrow sharp tools from microbes. Restriction enzymes cut DNA at specific spots, and DNA ligase seals the phosphodiester backbone back up after the cut. One cuts, the other pastes: keep those jobs apart and half the exam questions answer themselves.

Matching ends explain the golden rule of cloning. The same restriction enzyme must cut both the wanted gene and the plasmid vector, because only then do both pieces carry matching sticky ends that can join. A plasmid is a small DNA circle that works as the delivery vector into a bacterial host.

Run the steps in order: break cells open and isolate the DNA, cut gene and plasmid with the same enzyme, splice them together with ligase, and introduce the recombinant plasmid into host cells that then express it. The payoff is famous: bacteria given the human insulin gene brew human insulin, with no pig pancreases needed.

**Example.** Most attempted cells fail, so engineers flag the winners with marker genes, such as antibiotic resistance carried on the plasmid. Only cells holding the plasmid survive the screen. Bacteria admit new DNA three natural ways: transformation takes in loose DNA, transduction lets a virus ferry it over, and conjugation passes it cell to cell. Transcription is not one of them.

**Recap.** Cut both pieces with one enzyme, paste with ligase, deliver by vector, and screen with markers.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Selective Breeding and Genetic Engineering](https://lightmysky.com/learn/science/selective-breeding-and-genetic-engineering-mt_a3zTtiYrR2)
- [The Hardy-Weinberg Principle and Allele Frequencies](https://lightmysky.com/learn/science/the-hardy-weinberg-principle-and-allele-frequencies-mt_eJjwZ2qVAE)
- [DNA Structure and Base Pairing](https://lightmysky.com/learn/science/dna-structure-and-base-pairing-mt_PK4uNJeg_k)

## Opens up

- [CRISPR: A Bacterial Defence Turned into a Tool](https://lightmysky.com/learn/science/crispr-a-bacterial-defence-turned-into-a-tool-mt_0joPWRvOLw)
- [PCR, Electrophoresis and DNA Profiling](https://lightmysky.com/learn/science/pcr-electrophoresis-and-dna-profiling-mt_Sv1jV0XnsX)