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How can biotechnology spot a disease or a faulty gene, sometimes before any symptoms appear?

Describe how biotechnology is used in diagnosis and genetic screening, and discuss the implications

A focused answer to the O-Level outcome on diagnostics and screening. Detecting pathogens and faulty genes with PCR, probes and antibodies, and the benefits and concerns of screening.

Generated by Claude Opus 4.88 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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  1. What this dot point is asking
  2. The answer
  3. Examples in context
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What this dot point is asking

This outcome asks you to describe how biotechnology detects disease and faulty genes, and to discuss the implications of genetic screening. The techniques you have already met, PCR, probes and antibodies, come together here as diagnostic tools, and examiners also want a balanced view of the social and ethical side of screening.

The answer

Diagnosing infections

Biotechnology offers fast, sensitive ways to detect a pathogen:

  • PCR. A patient sample is tested, and PCR amplifies any of the pathogen's genetic material until it can be detected, confirming an infection even from a tiny trace.
  • Monoclonal antibodies. These bind to a specific molecule from the pathogen, and the binding gives a visible result, as in a rapid test strip.

Detecting faulty genes

To find a faulty gene or a disease-causing sequence:

  • DNA probes. A probe is a short piece of single-stranded DNA whose bases are complementary to a target sequence. It binds only where that sequence is present, showing whether someone carries it.
  • Sequencing. Reading the DNA can reveal the exact mutation responsible for a condition.

Genetic screening

Genetic screening tests people for faulty genes, sometimes before any symptoms appear. It can identify:

  • People who carry a faulty gene that they could pass on.
  • People who will develop a genetic disease.

The implications

Screening brings clear benefits but real concerns:

  • Benefits. Early detection, earlier treatment or monitoring, and the ability to make informed decisions, for example about having children.
  • Concerns. Anxiety from a positive result, the sensitivity of the data and risk of misuse (for example by insurers or employers leading to discrimination), questions of consent, and the difficulty of screening for conditions that cannot be treated.

Examples in context

Example 1. A rapid antibody test. A rapid test strip for an infection uses monoclonal antibodies that bind a protein from the pathogen, producing a coloured line if the pathogen is present. It gives a quick, simple result outside a laboratory, showing antibody-based diagnosis in everyday use.

Example 2. Screening newborns. Newborn babies are screened for certain treatable genetic conditions so that treatment can start early, before damage occurs. This illustrates the clear benefit of screening, while debates over which conditions to include show the ethical side.

Try this

Q1. State how PCR is used to diagnose an infection. [1 mark]

  • Cue. It amplifies any of the pathogen's genetic material in a sample until it can be detected, confirming infection.

Q2. Explain how a DNA probe detects a specific faulty gene. [2 marks]

  • Cue. The probe is a short single strand complementary to the target sequence, so it binds only where that sequence is present, showing whether the person carries it.

Q3. Give one benefit and one concern of genetic screening. [2 marks]

  • Cue. Benefit: early detection allowing earlier treatment or informed decisions. Concern: anxiety from results, or misuse of sensitive data leading to discrimination.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original6 marksDescribe two ways biotechnology is used to diagnose disease, naming the technique used in each.
Show worked answer →

Examiners want two distinct diagnostic methods with the technique named.

First, the genetic material of a pathogen can be detected using the polymerase chain reaction (PCR). A sample from the patient is tested, and PCR amplifies any of the pathogen's DNA (or DNA copied from its genetic material) that is present until it can be detected, confirming infection. This is used to diagnose viral and bacterial infections.

Second, monoclonal antibodies can be used to detect a specific substance, such as a protein from a pathogen or a hormone. The antibody binds only to its target, and this binding gives a visible result, as in a rapid test strip. This is used in tests for infections and in pregnancy tests.

A faulty gene can also be detected using a DNA probe, a short piece of DNA that binds to a specific sequence, showing whether the sequence is present.

What markers reward: two valid methods, each with a named technique, such as PCR to detect a pathogen's genetic material and monoclonal antibodies (or a DNA probe) to detect a specific molecule or sequence, with a brief correct explanation of how each works.

Original5 marksDiscuss the benefits and concerns of genetic screening for a serious inherited disease.
Show worked answer →

The answer should give balanced benefits and concerns.

Benefits: genetic screening can identify people who carry a faulty gene or who will develop a genetic disease, sometimes before symptoms appear. This allows earlier treatment or monitoring, helps people make informed decisions, for example about having children, and can reduce suffering.

Concerns: a positive result can cause anxiety and difficult decisions. The information is sensitive and could be misused, for example by insurers or employers, leading to discrimination. There are also questions about consent and about screening for conditions that cannot be treated.

What markers reward: at least two benefits (such as early detection, informed decisions, earlier treatment) and at least two concerns (such as anxiety, misuse of data, discrimination, consent), giving a genuinely balanced discussion.

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