Why is supplementing a gene more likely to succeed for a recessive condition than a dominant one?

One working allele is enough to produce a normal phenotype when the faulty allele is recessive. A dominant faulty allele still makes its harmful product, even with a working gene added.

What is somatic cell gene therapy?

Somatic cell therapy alters the genes in body cells of the affected tissue, such as airway lining cells. The change is not passed on to the person's children.

Why must somatic cell gene therapy often be repeated?

Many treated body cells, such as those lining the airways, die and are replaced within weeks or months. New cells do not carry the added gene unless treatment is given again.

CCEA A-Level Life and Health Sciences 0008

Experimental Techniques

Topic overview Standard solutions, titrations and qualitative tests Rates of reaction and organic preparations Physics measurements: oscillations, resistivity, lenses and critical angle Biological tests, colorimetry, chromatography and osmosis

Human Body Systems

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Physical Chemistry in Industrial Processes

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Brain ScienceDouble Award

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Medicine, Drugs and Clinical TrialsDouble Award

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Sound and LightA2 option

Topic overview Transverse and longitudinal waves and wave graphs Phase difference and the electromagnetic spectrum Outer, middle and inner ear Sound intensity and the decibel scale Standing waves, harmonics and resonance tubes Hearing response, phons and equal loudness curves Structure of the eye, rods and cones Accommodation, lens power and correcting long sight Total internal reflection and fibre-optic communication Dipole antennas, wireless networks and radar Attenuation of radio waves and the Doppler effect

Genetics, Stem Cell Research and CloningA2 option

Topic overview DNA structure and the evidence for the double helix RNA, genes and the triplet code Genotype, phenotype and monohybrid inheritance Dihybrid crosses, epistasis and the chi-squared test DNA replication and the Meselson–Stahl experiment Meiosis and genetic variation Insulin, factor VIII and chymosin from genetically modified microbes Recombinant DNA technology and gene cloning Genetic engineering, food supply and ethics Gene therapy and cystic fibrosis Genetic disease, screening and counselling Genetic fingerprinting and gel electrophoresis Stem cells, therapeutic cloning and their ethics

MicrobiologyDouble Award

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Oral Health and DentistryDouble Award

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Histology and PathologyDouble Award

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Analytical Chemistry TechniquesDouble Award

Topic overview Volumetric analysis in industry and healthcare Applied titrations of vinegar, indigestion tablets and bleach Redox titration of iron tablets and evaluating titrations Principles of colorimetry Colorimetric analysis of copper ore, aspirin and iron Thin-layer chromatography and its uses Visualising chromatograms and identifying painkillers and pigments Calorimetry and combustion Molar enthalpy and bond energy calculations Qualitative tests for cations and gases

Enabling TechnologyDouble Award

Topic overview ECG and EEG machines in patient monitoring Ultrasound and IVF equipment in fertility treatment Prosthetic limbs, hearing aids and cochlear implants Workflow and equipment in a medical laboratory Ongoing monitoring of a long-term condition Health data collection, databases and data protection

Genetics, Stem Cell Research and Cloning

Gene therapy and cystic fibrosis

3 things to know
A2 5

Overview

Gene therapy and its three approaches, somatic and germ cell therapy and UK law, the CFTR protein and cystic fibrosis symptoms, and early gene therapy trials with liposome and virus vectors.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is gene therapy?

Key term

State the three ways in which gene therapy can work.

Key term

Explain how gene therapy supplements a defective gene.

Questions from this subtopic

Each one with the model answer underneath.

1
What is gene therapy?
Model answer
Gene therapy treats a genetic condition by altering the genes inside a person's cells. A working allele is usually delivered to the cells that need it.
2
State the three ways in which gene therapy can work.
Model answer
Gene therapy can repair the defective gene or replace the faulty gene with a normal one. A normal gene can also be added while the defective one stays in position.
3
Explain how gene therapy supplements a defective gene.
Model answer
A working copy of the gene is added to the cells alongside the faulty one. The added gene makes the functional protein, masking the effect of the faulty alleles.
4
Why is supplementing a gene more likely to succeed for a recessive condition than a dominant one?
Model answer
One working allele is enough to produce a normal phenotype when the faulty allele is recessive. A dominant faulty allele still makes its harmful product, even with a working gene added.
5
What is somatic cell gene therapy?
Model answer
Somatic cell therapy alters the genes in body cells of the affected tissue, such as airway lining cells. The change is not passed on to the person's children.
6
Why must somatic cell gene therapy often be repeated?
Model answer
Many treated body cells, such as those lining the airways, die and are replaced within weeks or months. New cells do not carry the added gene unless treatment is given again.

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