Listen&Learn: Tetrachromacy

Learn about the rare eye condition that allows people to see more colours.

Pre-listening vocabulary

• genetic: passed down from parents to children through genes
• distinguish: to notice the difference between two or more things
• chromosome: a structure made of DNA
• mutation: a gene change that can cause someone to develop unusual traits
• colourblind: unable to distinguish as many colours as the average person
• identical: having no visible differences

Listening activity

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Gapfill exercise

Tetrachromacy is a rare genetic condition that causes some people to see more colours than usual. Most people have three types of cones in their eyes, which are to red, green, and blue light. However, tetrachromats have four. This allows them to see millions of colours that the person can’t distinguish. So far, very few true tetrachromats have been identified, and all of them are . This is because the gene for an extra cone is found on the X chromosome. If men the same mutation, they are likely to become colourblind instead. Scientists test for tetrachromacy by asking people to nearly identical colours by similarity. The average person will likely change their answer, but a tetrachromat will always sort these colours the same way.

Comprehension questions

See answers below

1. Tetrachromacy causes people to
   a. be more sensitive to blue light
   b. see perfectly in the dark
   c. distinguish more colours than the average person
   
2. Tetrachromacy has only been found in
   a. women
   b. young children
   c. artists
   
3. Scientists test for tetrachromacy by
   a. taking a DNA sample
   b. observing a person’s reactions to bright light
   c. asking a person to sort nearly identical colours

Discussion/essay questions

1. Do you think you see colours the same way as other people? Is this possible for us to know?

Transcript

Tetrachromacy is a rare genetic condition that causes some people to see more colours than usual. Most people have three types of cones in their eyes, which are sensitive to red, green, and blue light. However, tetrachromats have four. This allows them to see millions of colours that the average person can’t distinguish. So far, very few true tetrachromats have been identified, and all of them are female. This is because the gene for an extra cone is found on the X chromosome. If men experience the same mutation, they are likely to become colourblind instead. Scientists test for tetrachromacy by asking people to sort nearly identical colours by similarity. The average person will likely change their answer, but a tetrachromat will always sort these colours the same way.

Answers to comprehension questions

1c 2a 3c