The Secret Life of Twins: Nurtured Differences

How do Twins Relate to Nature Versus Nurture? (03:18)
Despite their shared genetic makeup, some “identical” twins don’t appear identical at all, which raises important questions about the role of environment in human development.

Identical Twins at Conception (01:56)

Each year in the U.K. identical twins are born to about 4,000 couples. This "miracle" of nature occurs when a single embryo inexplicably splits. The two new babies have identical DNA but will differences will emerge throughout their lives.

Exploration of Nature Versus Nurture (01:40)

For years scientists have been debating the impact of genes and environment on individuals. Studying twins is a unique way of exploring this journey. Identical twin doctors will undergo a series of test to reveal their physiological differences.

Study of Weight and Genetics in Twins (01:12)

The Department of Twin Research has run tests on thousands of twins. Most identical twins are similar in weight but studies have shown that genes do not tell the whole story.

Genetics and Lifestyle Influence Weight (01:05)

Identical twin brothers have a fairly substantial weight difference despite their identical genes. One is considerably more active than the other but is that the only reason for their weight difference?

Why Makes People Gain Weight? (02:15)

Because of the growing obesity problem it's crucial for scientists to understand weight gain. Identical twins are taking part in a study that shows habits formed during the teenage years play a major role in adult weight.

Is Appetite Determined by Genes? (02:33)

By studying twins scientists have learned that putting on weight actually changes fat cells. This explains why putting on weight is easier than losing it. Twin studies are also helping scientists identify the food sensitivity genes.

Twins Can Age Differently (02:30)

Twin studies have shown that lifestyles can affect the way genes shape bodies as well as age them. A set of identical twins does not appear to be aging at the same rate. Is it because one of them has had a significantly more difficult life than the other?

Skin Analysis of Twins (01:16)

To find out whether different life experiences have affected how old they appear a set of twins is visiting the L'Oreal Laboratories for a series of tests. Researchers hope to figure out which lifestyle factors affect the way people age.

Complex Relationship Between Environment and Genes (01:39)

A set of identical twins learn which of them has the oldest skin. The answer is surprising considering one has a much healthier lifestyle than the other. It seems that carrying extra weight seems to outweigh the effects of smoking and stress.

Biological Difference in Twin Cells (02:19)

Despite sharing identical genes, one twin has skin which appears younger but has cells that are aging faster. Cellular aging leads to more than wrinkles, it also increases the risk of many illnesses.

Why is One Twin Heavier Than the Other? (01:04)

An identical twin wants to know if events from his childhood could have left him more prone to weight gain than his twin brother. Perhaps chance experiences in childhood set a pattern that lasted into adult life.

Childhood Cancer in Identical Twins (02:00)

A set of identical twin girls were nearly indistinguishable before one was diagnosed with Leukemia. She was put on an intensive course of chemotherapy which made her lose weight and hair while her twin continued to grow normally.

Why Would One Identical Twin get Cancer but not the Other? (01:36)

Two years of treatment for Leukemia took a toll on the patient and her identical twin. Scientists have long suspected there is a genetic basis to Leukemia. Evidence suggests an infection probably triggered the disease.

Chance for Early Detection in Childhood Cancers (02:13)

A set of identical twins gave doctors unique access to the early stages of Leukemia when one was diagnose with the disease. They believe Leukemia is a result of chance environmental triggers and DNA.

How do Conditions in the Womb Shape Development? (01:50)

Twin studies continue to reveal how environmental factors affects adults and children and before birth. Ultrasound images give researchers an unprecedented view of life inside the womb.

Is ADHD Determined in the Womb? (00:45)

Just because twins share the womb doesn't mean they have identical experiences. If one twin has a greater share of the placenta they will receive more nutrients and oxygen. This could explain why some twins develop differently.

What Causes ADHD? (01:28)

Twins are genetically the same people but factors inside the womb and early in life can affect the way they develop. Differences in blood flow and nutrients inside the womb could be the reason why only one identical twin has ADHD.

Nature Versus Nurture and Sexuality (02:15)

Subtle environmental differences even before birth can play a part in shaping a person. A set of identical twins one of whom is gay, are looking for answer in the nature nurture debate.

Epigenetics: Link Between Nature and Nurture (02:16)

Studies have shown identical twins are more likely to share the same sexual preference than non identical twins. This suggests there is a genetic component to sexuality but scientist believe there is also an environmental factor.

What is Epigenetics? (01:08)

Epigenetics is the link between nature and nurture. The role of genetics and environment is compared to the relationship between sheet music and the composer of an orchestra. Epigenomes can produce different results from the same DNA.

Epigenomes and Sexual Orientation (01:57)

Identical twins are taking part in a study at UCLA to find out if epigenetics can explain why one is gay and the other is not. They discover that twins share the same genes but can use them differently.

How does Environment Affect Genes? (00:54)

Epigenetics is shedding new light on the nature nurture debate. Differences between identical twins make them perfect subjects for scientists for studying how environment can turn genes on or off.

Epigenetic Differences in Twins (03:06)

Identical twins have blood tests to measure genetic changes that may have occurred as the result of living different lifestyles. The results show that although they are genetically identical their lives have affected the way their bodies work.

Why is Epigenetics so Important? (00:43)

Epigenetics is so revolutionary that it's changing the way scientists think about some of the worlds most widespread and debilitating diseases, which are caused by the interaction between genes and environment.

Epigenetics and Disease (01:53)

DNA samples have been collected from identical twins where one has type one diabetes and the other doesn't to look for epigenetic markers. This research could help diagnoses and treat diabetes much earlier.

Genes are Controlled by Epigenetics (01:03)

Epigenetics is at the cutting edge of modern medicine. Studying twins may help explain how diseases are caused and how they might be treated. It has shown that profound influences take place between conception and birth.

Do Genes Determine Destiny? (02:05)

Watch as a set of identical twins boys is delivered by cesarean section. Although their shared DNA will make them incredibly similar their genes will be influenced by the lives they lead.