Sunday, 30 September 2012

Too many parents spoil the child?

When does a genetic donor become a biological parent and how many biological parents are too many? In this post, our guest blogger, REBECCA BOLLARD, looks at the recent technological developments around the possibility of three-parent babies.

In human fertilisation an egg cell is fertilised by a sperm cell, and each has 23 chromosomes. The fertilised cell has 46 chromosomes (the standard number for a human) and develops into an embryo. Chromosomes are made of DNA and exist in an area of the cell called the nucleus, and contain genes. This is what most people think of when talking about DNA – half comes from each biological parent and combines to form a new person. Every person has two biological parents no matter how complicated the legal or social arrangements may be.

This is, however, not quite the full story. Human cells also contain mitochondria, tiny organelles responsible for making a specific chemical that the cells need to function. Human mitochondria contain a small amount of DNA (often called mitochondrial DNA or mtDNA) in the form of a single chromosome. This chromosome is inherited exclusively from the egg cell and therefore the biological mother. mtDNA consists mostly of genes devoted to the maintenance and running of the mitochondria. Defects in these genes can lead to a range of serious diseases, including a range of incurable heart and muscle problems.

Several technologies may overcome mitochondrial disease. Pronuclear transfer (PNT) and maternal spindle transfer (MST) both allow the nucleus of the mother’s egg to be placed inside the egg from a woman with no mitochondrial issues. Thus, the resulting embryo would have three genetic donors – the man who supplied the sperm, the woman who supplied the egg nucleus, and the woman who supplied the egg and therefore the mtDNA. The first two of these would have supplied most, but certainly not all, of the DNA in the embryo (and resulting person). So, perhaps that person would have three genetic parents?

These techniques could also be used in other circumstances, such as where an intending mother has no eggs or has gone through menopause. Scientists believe they can take a cell from elsewhere in a woman’s body and halve the chromosomes using electricity. This cell could then be used with the egg cell (and mtDNA) of another woman.

The UK Human Fertilisation Embryology Authority (HFEA) recently began a consultation on whether such techniques could be used to help the 1 in 200 children born every year in the UK with mitochondrial diseases. This has led to much discussion in the press, including in the Daily Mail and in The Guardian. This follows earlier works by the Nuffield Council on Bioethics that such techniques would be ethical once proved safe and efficient.

Bioethics professor John Harris argues that mtDNA donors would not be genetic parents as “DNA contained in the donated mitochondria comprises much less than 1% of the total genetic contribution and does not transmit any of the traits that confer the usual family resemblances and distinctive personal features... No identity-conferring features are transmitted by the mitochondria”. He then goes on to argue that he would be more upset at having a mitochondrial disease than “having some third-party DNA in my genome”.

So, when does a genetic donor become a biological parent? The two people donating nuclear DNA are obvious candidates, but what about mtDNA donors? What about gestational surrogates, particularly as the evidence builds that gestation is not a simple relationship (see e.g. the research article by Chen et al in Plos One)? Does it matter, when the biological, social, and legal aspects of parenthood are split more than ever?

Should the number of parents in technology-driven reproduction matter? Or is it irrelevant when we’re talking about serious and otherwise incurable disease?

Tuesday, 11 September 2012

Do images colour perceptions?

With the increasing use of functional Magnetic Resonance Imaging (fMRI), the activities of a human brain at work are now routinely depicted in three-dimensional colour images. These attractive pictures of the brain are near mandatory appendages to news stories on neuroscience in the popular media and have been shown to have a persuasive effect on readers.

In an article in Cognition a few years ago, David McGabe and Alan Castel had famously shown how brain images had a hugely persuasive influence on public perceptions of stories on neuroscience. These images affected people’s judgements of scientific reasoning because they provided a tangible physical representation of brain activity.

One of the reasons of this appeal of brain images is, as John Grohol says, quite simply because “the pretty, compelling pictures of fMRI” add a colourful layer to otherwise boring psychological research – they “seem to illustrate a direct, causative relationship … even if one doesn’t exist.” This is, of course, a major challenge and, as Grohol points out, fMRI images are not always an accurate reflection of a brain’s activity and does not capture “the complexity of human behaviour.”

So yes, fMRI brain images have a persuasive influence on readers of popular science stories. But do these images have a greater persuasive effect than other kinds of images on how readers perceive a story?

Not really, going by a new study by David Gruber of the City University of Hong Kong and Jacob Dickerson of Georgetown College, USA. In an article forthcoming in the Public Understanding of Science, the two researchers report on a study in which they monitored the effect on participants of a variety of images attached to news articles on neuroscience. The images shown to the participants included fMRI images, artistic drawings and still images from science fiction films. “There is no significant difference between readers’ evaluations of an article regardless of the associated image,” the researchers say.

What this means is that each image may be persuasive in its own right. But there’s no way to predict if one kind of image is more persuasive than the other at a general level. This then is a significant extension of the McCabe & Castel study.

As Gruber and Dickerson point out, research would need to explore how images interact with a specific text and the specific context of a particular reader to affect understanding of a news story on neuroscience.

In another study focused more broadly on the impact of pictures accompanying true or false claims, Eryn Newman, a PhD student from Victoria University of Wellington, New Zealand, with researchers from the University of Victoria in British Columbia, Canada, found empirical evidence for the notion of “truthiness”— popularised by US comedian and satirist Stephen Colbert. Colbert defines truthiness as “the truth that you feel in your gut regardless of what the facts support.” The research, published in Psychonomic Bulletin and Review, found that people are more likely to believe a claim, even if it is untrue, if it is accompanied by decorative pictures:
In a series of four experiments in both New Zealand and Canada, Newman and colleagues showed people a series of claims such as, “The liquid metal inside a thermometer is magnesium” and asked them to agree or disagree that each claim was true. In some cases, the claim appeared with a decorative photograph that didn’t reveal if the claim was actually true—such as a thermometer. Other claims appeared alone. When a decorative photograph appeared with the claim, people were more likely to agree that the claim was true, regardless of whether it was actually true.