What do we really know about earlobe genetics?

My husband and I both have attached earlobes. Our newly born son has detached earlobes. How is this possible since attached earlobes are recessive?

- Curious

That is a great question. Many of us learned in high school that attached earlobes are recessive, and it is easy to find that information repeated on the web as an illustration of dominance patterns. An example is the detailed treatment at the Singapore Science Center, which explores various possible parental combinations and concludes that "if both parents were homozygous recessive, they could not have a child with the dominant allele." That is certainly true, and it seems to make a liar out of Curious. Was her child switched in hospital? Should Curious become Alarmed or Suspicious?

I don't think so. I could not find the source of the "fact" that attached earlobes are recessive. I consulted OMIM (the Online Mendelian Inheritance in Man), and they have very little (OMIM 128900). What they do have calls into question the assumption that "attached earlobes are recessive."

Free earlobes are dominant in the view of some. Dutta and Ganguly (1965) suggested polygenic inheritance. There is a variety that is perhaps better classified as 'lobeless' than 'attached.' Lai and Walsh (1966) concluded that 'a simple Mendelian gene effect is unlikely to be responsible for the earlobe types.'

The other issue raised here is whether or not free earlobes is even a bivariate trait (in which case everyone's earlobes could be categorized as either attached or detached). That is necessary for simple dominance to make sense. In the words of students from Willowbrook high school who did a study of this, "it's harder to tell earlobes, so the count on these could be less accurate." OMIM states that "there is a variety that is perhaps better classified as 'lobeless' than 'attached.'" Different forms might show different patterns of inheritance.

I suspect that this, along with a large number of ordinary traits, will be examined anew in the era of personal genomics. For example, the people at deCODE genetics just published a report on the genetics of hair and skin pigmentation (Sulem et al., 2007: Nature Genetics 39:1443, PMID 17952075). Perhaps earlobes will be next.

This question may be most important as a cautionary tale about genetics education. Teaching students about earlobes seems very innocent, but this case illustrates why oversimplification might not be prudent.

What ancestry companies provide actual genetic data?

This question is inspired by an article in today's New York Times business section ("DNA Tests Find Branches but Few Roots"). The article is nice in that it compares the cost of ancestry testing by various companies, shows that results differ, and quotes Henry Louis Gates Jr. making reasoned assessments of the role that DNA testing can play. However, the article fails to say which companies provide customers with the raw genotype information that they can use to make their own assessments as more information becomes publicly available.


This map (from the article) shows the results returned to the author (Ron Nixon) from five different companies. Presumably, the actual genetic information they gathered is a bit less variable than their interpretation. If I paid to have my DNA analyzed, I would want the actual data so that I could make my own interpretations using the best information available from all sources.

The article lists 20 companies that will test your DNA for the purpose of learning about ancestry. Can anyone tell us which ones provide the client with the actual information (sequence or polymorphism data) that can be compared with published genetic demographic data?

Is race "real"?

Someone wrote in "wondering what the current stance is with geneticist in regards to whether different human races exist or not." This important question has been discussed at length already, and I refer readers to a Social Sciences Research Council forum on race, the special issue of Nature Genetics on race published in November of 2004, and an edited volume by Jefferson Fish. I side with those who feel that race, as it is normally understood, is a social construct. Those biological definitions that might be partially valid for humans differ significantly from the way the concept is normally used in our society. However, others argue for the importance of considering "ethnicity" in clinical trial design (Taylor et al. 2005), and the drug BiDil has been licensed exclusively for African-Americans (for a recent news report in "The Times" click here).

So, my answer to this questions has been given before.

It seems to me that if a drug differs in either safety or efficacy for one "race" or another, then the underlying basis is probably either a genetic difference or a cultural difference. In the first case, the relevant genetic difference itself, or a related biomarker, would be much more reliable than popular notions of race. On the other hand, if the basis is cultural, the relevant practice (such as lifestyle or diet) should be identified. I was therefore gratified to see Nature Genetics publish this letter from Jonathan Kahn making the case against the misuse of race, as well as a sidebar showing how the media has misrepresented their own statements.

However, additional answers are welcomed.

What can I learn about my ancestors from my DNA?

What can I learn about my ancestors from my DNA? What companies provide this information? How much does it cost? What exactly do I learn?

How does this site work?

This site, "Information on Genes" (ongenes.com) is a place where answers to questions on genes, genetics and genomics are provided by experts in the field.

The site differs from a blog in that answers will be provided by many experts in the field. If a question falls in the area of expertise of a specific researcher, then an answer from that researcher may be sought. The site is like wikipedia in that many people will contribute to the final product, but it is different in that everyone who answers a question must identify themselves. Answers are posted as "comments" which must be approved. Inappropriate answers will not be approved. The site resembles a forum in that an ongoing discussion is possible, but differs in that every set of answers will be maintained as a permanent page. Questions on breaking news are encouraged only if the answers will still be of interest in a year or two.

To ask a question, send email to questions@ongenes.info.
All questions will be posted anonymously. Your question may be edited, merged with another question or published sometime in the future. However, you will get a reply to your question by email in any case, and if you don't want your question to be anonymous, then say so in your email.

To answer a question, use the comment feature.
We are looking for answers from people with some expertise, and you will be asked to log in so that we know who you are. If you have an account with blogger (Google) and are logged in, you can answer simply by clicking on the "comments" link. If not, create a Google account and a profile that tells us who you are. We are looking for answers from experts in the field, but have no desire to censor appropriate answers from anyone who lets us know their credentials.

Our hope is that this site will provide useful information to anyone trying to understand genetic tests, including professionals in the field.