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Can an ancestor disappear from your DNA?

An ancestor can belong to your family tree without contributing a surviving segment of your DNA. Recombination and transmission pass on a selection of earlier generations’ genetic material, rather than a complete archive of the pedigree. Even a surviving contribution is different from one a particular test can reliably detect.

3–7 min

Questions you could explore

  • How can siblings share the same family tree but inherit different genetic paths through it?

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Health and the body

How does daylight set the body’s clock?

Feeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

3–5 min

How does daylight set the body’s clock?

Health and the body3–5 minFeeling sleepy at night involves more than counting the hours since you woke up. Internal daily rhythms respond to outside cues, with light helping coordinate the body's sense of time.

Health and the body

How does a vaccine give the immune system a memory?

The immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

4–5 min

How does a vaccine give the immune system a memory?

Health and the body4–5 minThe immune system can respond differently to something it has encountered before. Vaccines make use of recognition and memory, though different vaccine types introduce the relevant information in different ways.

Health and the body

Why won’t an antibiotic treat a viral cold?

The word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

2–3 min

Why won’t an antibiotic treat a viral cold?

Health and the body2–3 minThe word infection covers illnesses caused by very different organisms. An antibiotic that helps against certain bacteria has no matching target in the viruses that cause a cold.

Can an ancestor disappear from your DNA? | Speech Topic | speaking.app