Inherited conditions
Distinguish sickle cell disease, thalassaemia and inherited colour vision deficiency from infections, without treating inheritance as contagion or certainty.
On this page
Staying Healthy · about 25–35 min
What you need to understand
Inherited conditions are passed through genetic information, not ordinary contact.
Definitions
- hereditary
passed from parents through inherited information
For example: A hereditary condition is not contagious.
Explanation
Hereditary means passed through genetic information from parents. A gene is a unit of inherited information that can affect how the body develops and works. This is a different route from an infection caused by bacteria or viruses.
Sickle cell disease and thalassaemia are inherited conditions affecting haemoglobin, the oxygen-carrying substance in red blood cells. In sickle cell disease, altered haemoglobin can make red cells rigid and sickle-shaped. In thalassaemia, haemoglobin production is affected. Both can impair the blood’s ability to deliver oxygen.
Inherited colour vision deficiency makes certain colours
harder to distinguish. It usually does not mean seeing no colour. Colour
vision problems can also have acquired causes, but the example studied here is
the inherited form. The NHS explanation of colour vision deficiency
Family information alone does not diagnose an individual or prove that every child must have the same condition. The outcome depends on the inherited information. You do not need to calculate inheritance probabilities here; distinguish the named hereditary examples from infectious transmission.
Pause and say it: Hereditary means inherited from parents, not caught through ordinary contact.
Common mistake
Tempting wrong idea: “A condition runs in a family, so it must spread from one family member to another like an infection.”
Why it fails: Relatives can share inherited information. That explains an inherited condition without requiring a microbe to spread through contact.
Use this instead: Identify the mechanism. Genetic information passed from parents explains heredity; pathogens spreading between people explain contagious infection.
Worked Examples
Modelled example 1
Identify how a condition is passed on
Problem
An information card says thalassaemia is inherited and affects haemoglobin. A learner says it must be an infection caught from a friend. Explain the error.
Study the worked solution
Use the cause described
Method
Distinguish inherited information from a pathogen.Reason
Two conditions can both affect health without having the same cause or way of being passed on.
Working
Thalassaemia is an inherited condition: genetic information passed from parents affects haemoglobin production. It is not a bacterial or viral infection acquired from a friend. Sharing ordinary classroom space does not pass on this inherited condition.
Common misconception 2
Inherited does not mean contagious
Learner response
“Inherited colour vision deficiency means seeing no colours, and it can spread between classmates who share pencils.” Correct both parts of this claim.
Correct the effect and the transmission
View solution step by step
Keep the two corrections distinct
Method
Explain what is affected and how it is inherited.Reason
The name of a condition does not justify either an exaggerated effect or an infectious cause.
Working
Inherited colour vision deficiency usually makes certain colours harder to distinguish; it does not usually mean seeing no colour. The inherited form is passed through genetic information from parents, not through sharing pencils.
For the original kidney-support comparison, continue to dialysis and transplantation.
Guided practice
Try it with support
Explain why sickle cell disease, thalassaemia and colour deficiency are called hereditary rather than contagious.
Distinguish inheritance from spread of microbes.
Check the guided answer
Answer: They can pass through inherited genetic information; they are not caught through ordinary contact.
Check: This classification does not diagnose an individual or mean every child in a family must have the condition.
Practise and continue
Practise this
An information card describes thalassaemia as inherited. A learner proposes avoiding a classmate’s desk to prevent inheriting it. Explain why that action does not address the cause.
Need a hint?
Compare inherited information with infectious transmission.
Check your answer
Answer: Thalassaemia is passed through inherited genetic information, not through a classmate’s desk. Avoiding that desk cannot prevent inheritance. Hygiene has a different purpose: reducing transfer of harmful microbes.
Check: Sharing a classroom does not pass on an inherited condition.
Think like a scientist
A fictional claim says a kidney transplant prevents children from inheriting colour deficiency. Find the first error.
Check the reasoning
A transplant supports organ function; it does not change the genetic information a person inherited or the rules of inheritance.
Remember: Inherited does not mean infectious, and transplantation is not vaccination.
One-minute check
Hide the page. Name the three inherited examples and explain how inheritance differs from contagion.
Explain why inherited colour vision deficiency need not mean seeing no colours, and why family information alone cannot diagnose a person.
Correct this claim: “A condition running in a family must spread by ordinary contact.”
Syllabus and review details
- SEC G1 Science 2027 · 2027
Content structure and syllabus content, PDF pages 8–17
Last reviewed: