Genetic Differences Between Identical Twins

by Dr. Hsien-Hsien Lei
Posted February 20, 2008 in DNA in General

Identical (monozygotic) twins Raymon and Richard Miller had better watch out. The two were embroiled in a paternity suit that alleged both had slept with the same woman on the same day and nobody knew which brother had impregnated her. In May 2007, the judge decided that Raymon is the legal father of the child who was subsequently born although child support was split between the two brothers.

Standard paternity testing examines 16 DNA markers which is enough to make them over 99.99% accurate. In the case of the State of Missouri and Holly Marie Adams vs. Raymon and Richard Miller, the paternity test showed that the two brothers both had a 99.999% probability of being the father. There is currently no commercially available test that can determine which of the twin brothers passed his DNA to the child even though there are ways in which the genomes of identical twins differ.

Epigenomic chemical modifications. Researchers at Ohio State University found epigenetic changes in twins’ genomes that increased as pairs of twins aged. One of the main epigenetic processes that occurs to our DNA is methylation which can be caused by environmental exposures, such as diet and physical activity. Methylation can lead to differences in gene expression and as we age, the amount of DNA methylation increases. So, it’s expected that identical twins will grow less and less similar in their patterns of DNA methylation and gene expression as their lives progress especially if their lifestyle habits and surroundings differ greatly.

DNA copy-number-variation profiles. Another way in which the genomes of identical twins may differ is in copy number variation (CNV) that appears as segments of DNA that are missing, occur in multiple copies, or have flipped orientation in the genome. Identical (monozygotic) twins have been found to have different CNVs which could explain why even identical twins are not truly identical in appearance or other physical characteristics despite similar environmental exposures. For example, one twin sometimes develops a disease while the other does not. (HT: DNA Direct Talk)

What does this mean for Raymon and Richard Miller? DNA methylation patterns and copy number variations can be definitive in a paternity case if differences between the brothers are identified. Then, by comparing the same genomic regions in the child, it may be possible to see who the s/he more closely resembles genetically keeping in mind that the child is also accumulating his/her own DNA methylation and CNVs. While this type of genetic analysis isn’t currently available, it will most likely be available in the child’s lifetime. I would suggest that the Millers’ love child or his/her guardian store DNA from Raymon and Richard Miller for future analysis.

Update:: John Hawks has more.

Photo credit: Wellcome Images under Creative Commons.

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DNA Toys: Ben 10 and Digimon Digivice

by Dr. Hsien-Hsien Lei
Posted February 18, 2008 in DNA Fun

Toymaker Bandai is all about DNA. Ben and his 10 (and counting) alien hero alter egos have a Ben 10 DNA lab in which you can enter codes for two aliens which the lab will then combine to create a new mutant alien hero.

Update:: Here are the secret codes to use in the Ben 10 DNA Lab.

And then there’s the new Digimon Digivice unveiled at New York Toy Fair 2008 that features a DNA chip. There’s a scanner that will read the chips and allow the players to collect DNA skills and boost their strength.

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DNA Video: deCODEme

by Dr. Hsien-Hsien Lei
Posted February 16, 2008 in DNA Podcasts and Videos

deCODE genetics introduces deCODEme, a revolutionary new service that allows individuals to have their own genome scanned.

via ScienceRoll

Tags: decode, genetics, genes, dna, decodeme, genomics, personal genomics

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Eye on DNA Headlines for 15 February 2008

by Dr. Hsien-Hsien Lei
Posted February 15, 2008 in DNA Testing, DNA and Genealogy, Eye on DNA Headlines

• The Teaching Company sells a 24-lecture intro to genetics course, Understanding Genetics: DNA, Genes, and Their Real World Applications, taught by Dr. David Sadava of The Claremont McKenna, Pitzer, and Scripps Colleges. After watching a preview, I can say that it’s not much more interesting than the lectures I sat through in college but for people who learn better by listening and watching, rather than reading, it may be valuable. (HT: GENEALOGY-DNA)
• Please welcome the latest members of The DNA Network. We now number 46!

  *Next Generation Sequencing from CLC bio
  *Mailund on the Internet
  *Buzzyeah
  *FinchTalk
  *Genetic Future
  *PredictER

• Gotta have this squishy, squashy, lumpy light-up DNA ball from HearthSong! (HT: Kristina)
• An oldie but funny on genetic genealogy from one of my favorite writers at the New York Times – Michelle Slatalla.

  Marie Antoinette, Is That You?

• Mary Beth Faller of The Arizona Republic asks: Is a gene test right for you? It’s got a negative slant to it (of course) but the right sidebar has some good basic information on DNA testing.

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DNA Quote: Genetic Anthropologist Spencer Wells

by Dr. Hsien-Hsien Lei
Posted February 15, 2008 in DNA Quotes and Excerpts

From a conversation between writer Will Self and genetic anthropologist Spencer Wells published at Seed:

Spencer Wells: I think there’s something inherent in humans that, yes, makes us want to migrate, but also to have that connection to place, even though we’re moving. I think there is something of a wanderlust in our DNA, something that makes us want to explore a little bit further, but at the same time we want to actually be in the place. The way we travel today, you’re not in the place. There’s never any “there” there.

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DNA Podcast: Gene Journalism on BBC Radio 4

by Dr. Hsien-Hsien Lei
Posted February 14, 2008 in DNA Podcasts and Videos

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Gene Journalism 11th Feb 08

Can we rely on reports that link various illnesses and conditions with our genetic make-up? Guests: Michael Blastland, author of ‘The Tiger That Isn’t: Seeing Through a World of Numbers’ John Illman, former chairman of the Medical Journalists Association

HT: Snowy

(>> Start a discussion!)

DNA Videos: Genetic Testing on NBC Nightly News

by Dr. Hsien-Hsien Lei
Posted February 13, 2008 in DNA Podcasts and Videos, DNA Testing

Yesterday, Robert Bazell of NBC Nightly News continued the series, The Truth About DNA, with The downside of DNA testing (video below). I admire their willingness to tackle such a timely topic but with segments of less than three minutes, not much can be explored. The general gist of the genetic testing videos is negative with a focus on Myriad’s BRACAnalysis genetic test for breast and ovarian cancer risk. Of course, it’s safer to recommend we all stay away from the scary unknowns of genetic testing but I firmly believe that educated consumers should be allowed to make their own decisions without the controlling arm of babysitters.

In the above video which was aired, Hank Greely of Stanford Law School says he’s “scared of what’s going on in the genetic testing marketplace.” Bazell follows up with a blog post saying, “There is a frightening lack of government regulations.”

Are they easily scared? Or is there merit to their fear?

I think it’s a bit of both. When it comes to our DNA, any sane person would feel some trepidation especially if they’ve got an overactive imagination like me. It seems we have two choices:

1. Get a glimpse of what might be in store for our future health.
2. Cross that bridge when we get to it.

I’d guess most of us fall into the second category and there’s nothing wrong with that! Life is far from certain especially when it comes to the predictive power of genetic testing. I may test positive for a cancer gene and get run over by a bus tomorrow. Would it matter then?

Yale genetic counselor Ellen Matloff believes it would because of the impact genetic testing results have on extended family. Here’s her golden quote:

The genetic test you have is only as good as the interpretation.

Matloff recommends that people undergoing genetic testing send a letter to their family members inviting them to an open discussion of the results. Here’s a sample letter you could use courtesy of me:

Dear Mom and Dad,

I bought a $1,000 DNA test last month. It wasn’t painful at all. Although when I saw that I might have inherited the gene for short temper, I wanted to put a fist through the wall. So I guess I was right to blame you for everything. Let me know if you want to talk about our DNA some more.

Love,
Johnny

(JUST KIDDING!!)

More videos below the jump.

Continue reading…

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DNA Video: The Truth About DNA on NBC Nightly News

by Dr. Hsien-Hsien Lei
Posted February 12, 2008 in DNA Podcasts and Videos

This week’s NBC Nightly News features a special series from February 11 through February 13 called The Truth About DNA. Stories include Genealogy For Sale (video below), Testing Your Genes, and Criminology.

HT: GENEALOGY-DNA

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deCODE Launches PrCa Prostate Cancer DNA Test

by Dr. Hsien-Hsien Lei
Posted February 12, 2008 in DNA Testing, DNA and Disease

The genetic testing market is highly competitive. No sooner does one company launch a first-of-its-kind test than another launches a similar one. In January, Proactive Genomics made available the $300 prostate cancer genetic test, Focus5 Prostate Cancer Risk Test, that examines five SNPs. (Although it’s not clear from their website how consumers can order the test.) Less than a month later, deCODE Diagnostics follows suit with the $500 deCODE PrCa test that analyzes eight SNPs for prostate cancer:

• Three on chromosome 8 (8q24)
• Two on chromosome 17 (17q12, 17q24.3)
• One on chromosome 2 (2p15)
• One on chromosome 11 (11q13.3)
• One on X-chromosome (Xp11.22)

deCODE states that the relative risk of prostate cancer for those of European ancestry who are homozygous at all eight is 17.6 times higher than the reference group.

• About 40% of the population has a genotype combination of the tested markers that have an increased relative risk (>1) over the general population
• About 10% of the population has a genotype combination that confer an average two-fold relative risk
• About 1% have relative risk above 3

The deCODE PrCa test is available from physicians and medical practitioners. Patients can kick start the process by downloading the test order forms and bringing them to their doctor’s visit.

There is a strong market for prostate cancer testing. Prostate cancer is the second leading cause of cancer-related death in American men. According to the National Cancer Institute, there were almost 220,000 new cases of prostate cancer in 2007 and over 27,000 deaths attributed to the disease. The American Cancer Society recommends screening for men starting at age 50 with men at higher risk receiving screening starting at age 45.

Screening, however, is controversial. Some studies have not observed a decrease in mortality rate from early screening for prostate cancer. Early detection at younger ages may not be particularly useful because prostate cancer develops slowly and would be better left alone until many years down the line. deCODE literature emphasizes that the five-year survival rate among prostate cancer patients is 100 percent due to early detection.

From the Prostate Cancer Foundation:

…there is no unanimous opinion in the medical community regarding the benefits of prostate cancer screening. Those who advocate regular screening believe that finding and treating prostate cancer early offers men more treatment options with potentially fewer side effects. Those who recommend against regular screening note that because most prostate cancers grow very slowly, the side effects of treatment would likely outweigh any benefit that might be derived from detecting the cancer at a stage when it is unlikely to cause problems.

The Independent asks “The Big Question: Are we on the brink of a breakthrough in the fight against prostate cancer?”

Can prostate cancer be beaten?

Yes

• A new genetic test will enable men at high risk to be identified for regular screening
• More accurate blood tests based on a new gene target could mean earlier identification of the disease
• Treatment could be offered to those men with fast-growing, aggressive cancers

No

• The existing PSA blood test cannot distinguish between a cancerous prostate and a benignly enlarged one
• Even when cancer is diagnosed there is often no way of knowing if it needs treating
• Prostate cancer is unique in that it can be so slow to develop that more men die with it than from it

More on prostate cancer genetic testing from Cancer Genetics.

NB: DNA Direct (for whom I work) partners with deCODE to offer free pre- and post-testing consultation and genetic counselling.

Photo credit: Wellcome Photo Library, Colour artwork of the urinary bladder with its two ureters and also the seminal vesicles and the ampulla of vas, leading to the vas deferens. The prostate gland and its passages are at the base of the bladder in this posterior drawing.

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DNA Podcast: Futures in Biotech with Dr. George Church Part 2

by Dr. Hsien-Hsien Lei
Posted February 11, 2008 in DNA Podcasts and Videos

More than four months after Marc Pelletier first interviewed Dr. George Church for the Futures in Biotech podcast, he’s back in Part 2: From Human Genome Project to Your Genome Project.

Well, I [Marc Pelletier] wanted to have him back to discuss two technological revolutions that are currently happening in biotech. The first is the personal genome. Why do I call it a revolution, as opposed to an evolutionary technological step? Because it changes how we make medical decisions: from being based on statistics and family histories, to decisions that are based on our true molecular anatomy, our own genome. The second revolution is the new field of synthetic biology: creating tailored organisms, not by simply adding or subtracting a single or a few genes as for GM foods, but redesigning organisms from scratch. Dr. Church has been a key player in both these revolutions and his insights are just about the best out there.

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