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ear lobes

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489908.  Mon Jan 26, 2009 6:18 pm Reply with quote

Hi There. Just watched Q.I. (Dave,26th jan 2009) Stephen said that if your parents' earlobes don't dangle, then yours wont either. Now, if your ma's don't dangle, and your pa's do, presumably yours could do either, dangle or join. This being the case, if you're born with dangly earlobes,and have a child with someone who also has dangly earlobes, might the non-dangling gene from the grandparent become apparent (throwback).
This is puzzling me.Can anyone enlighten me please. Thank you. Patsycastle

489911.  Mon Jan 26, 2009 6:28 pm Reply with quote

Yes, you are right. Dangling earlobes are dominant and attached earlobes are recessive. If the parents had a heterozygous (mixed) genotype, say Ee and Ee, then the alleles could combine in a child to form ee, attached lobes.

What Stephen said was:
"If you both have attached lobes as the mother and father, then your child must have attached lobes, too."
"If a child has hanging lobes, and both his parents have lobes attached, then something's amiss."

This is also unobjectionable. Because attached earlobes are recessive, in order to have attached lobes, each parent must have two recessive alleles (ee and ee). It is therefore impossible for them to have a child with hanging earlobes, which requires a dominant allele.

489953.  Mon Jan 26, 2009 7:32 pm Reply with quote

Thank you MinervaMoon, for your speedy reply to my question. Patsycastle

491259.  Wed Jan 28, 2009 12:45 pm Reply with quote

Well explained. However, the story is not that simple. Earlobe attachment does not appear to be a single gene effect. I think it's important to point this out, because it is not 100% reliable to make assumptions about parentage by looking at earlobes, and not worth sueing your hospital over mixed-up babies without further evidence!

Tongue rolling, as often used in the UK as an example of Mendelian inheritance, is also not a simple story. Studies are confounded by the ability to learn to roll the tongue (i.e. environmental effects).

For more check out Online Mendelian Inheritance in Man.

491320.  Wed Jan 28, 2009 2:05 pm Reply with quote

Thanks Storidoc and welcome to the forums :-)


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