Sunday, October 09, 2005

Genetics in the Movies   posted by DavidB @ 10/09/2005 03:58:00 AM

Anyone with an interest in human genetics will occasionally be amused or annoyed at the treatment of genetics in films and TV. I will give my own Oscar (TM) nomination for the worst genetic mistake in the movies, but readers may have other candidates.

I am not thinking so much of movies like Gattaca with a specific genetic theme, as of the general disregard for genetics shown in casting and storylines. For example, I recall a film where a male character was said to have an identical twin sister. [Note 1]

On a more mundane level, we often see blue-eyed screen couples with brown-eyed children, siblings of wildly different height or features, and other genetic improbabilities. You might think that casting directors would at least make sure that the actors were of the right racial origins for the characters, but even this is often ignored. I recall a British TV series where a Mexican character was played by a South Asian, and now on Lost we have an Iraqi played by an Anglo-Indian [Note 2]. But this probably doesn't matter to most Western viewers (myself included) as all brown dudes look much the same to us! :-)

There is a similar looseness in the casting of black (African-American) characters. Remember the Cosby Show, where the five children ranged in colour from dark chocolate to nearly white, with two of the children much lighter than either of their parents? This is not quite impossible, but if I were Dr Huxtable I would demand a paternity test.

I don't find any of this too distracting unless it is significant to the plot. It is more of a problem where the casting makes some key element of the plot genetically incredible. For example there are several movies where a character with black ancestry is 'passing for white'. For credibility the actor needs to be a borderline case: not Wasp-white, but not obviously black either. The classic weepie Imitation of Life was plausible from this point of view, as was a 1950s British film called Sapphire. But Anthony Hopkins (in The Human Stain) is not a suitable choice as someone passing for white! Then there was a film where Robert Duvall, playing a Southern redneck white, discovers that his biological mother was black. Oh, please! It would be credible if he discovered a black great-grandparent, or at a pinch even a grandparent, but not his mother. The opposite situation arose in Mike Leigh's Secrets and Lies, where an adopted black woman, tracing her natural parents, discovers to her shock that her mother is white. The casting of this role is tricky: it needs to be someone black enough not to suspect their mixed ancestry (which in England is hardly a rarity), but not so black that it is incredible. There may be actresses who meet this specification, but Marianne Jean-Baptiste is not one of them. She is just too black to have a white mother, especially a pale redhead like Brenda Blethyn. For me, at least, this genetic implausibility wrecks the central element of the plot.

But my Oscar nomination for most disastrous genetic blunder in the movies (and the case which prompted me to write this post) has nothing to do with race. It comes in a recent film called Tiptoes.

This apparently had a limited cinema release last year, but is now available on DVD. I must admit my main reason for watching it is that it features Kate Beckinsale, and I would watch almost anything with Kate in it. (Though I may draw the line at the Underworld sequel. I sympathise with the critic who said he would rather stick needles in his eyes than watch Underworld again.)

Tiptoes is about a young woman artist (Beckinsale) who is engaged to a tall, hunky firefighter (Matthew McConaughey). So she is shocked when she discovers that most of his family are dwarfs, including his parents and his twin brother (played by Gary Oldman with kneepads). The rest of the film explores her reactions as she gets to know the family and the wider dwarf community, and the resulting tensions between her and McConaughey.

Of course, there is nothing impossible about two achondroplasic dwarfs (as the parents seem to be) having a non-dwarf child, though I rather doubt that a dwarf woman could bring twins safely to term. The problem comes with another major part of the plot. Shortly before she discovers McConaughey's family secret Beckinsale has learned that she is pregnant. Naturally she is worried that the baby might be a dwarf. So does McConaughey reassure her that the chances are minuscule? No, he says it is 'definitely possible'. And she goes on to consult various other people, including a dwarf doctor, all of whom solemnly warn her that it is quite likely. And to cap it all, when the baby is born, it is a dwarf!

Whatever were they thinking? The most common forms of dwarfism are due to a dominant gene defect. A non-dwarf (like McConaughey) would therefore not have the relevant gene, and would be at no more risk of having a dwarf baby than anyone else. It is true that some rare forms of dwarfism are due to recessive gene defects, but in this case McConaughey's dwarf parents would be homozygous, and McConaughey would himself be a dwarf. [Note 3] Either way, the storyline seems genetically absurd. Maybe there is some rare form of dwarfism in which the defect is dominant (in the sense that it can be expressed in the heterozygote) but unpredictable in its effects, so that the bearers of the gene may be either dwarf or non-dwarf. If so, I stand corrected. But even in this case the film would be seriously misleading, as it gives quite the wrong impression about dwarfism in general. Were the writers and director simply ignorant of the genetic facts, or did they deliberately ignore them for the sake of a more dramatic storyline? If the latter, they are doubly culpable, as one of the aims of the film is to dispel prejudices and misunderstandings about 'little people'. The average viewer will draw the false conclusion that it is never safe to have children with any relative of a dwarf.

But don't let this put you off watching it! Genetics apart, it's an unusual and surprisingly enjoyable film with good performances from the leads (especially Oldman) and a large cast of small supporting players. It ends abruptly with Beckinsale breaking up with McConaughey, and on the brink of a romance with Oldman. Apparently the director (Matthew Bright, who made the cult classic Freeway with a young Reese Witherspoon), wanted the outcome to be more explicit, but the financial backers vetoed this and took control of the final cut. The world is not yet ready for dwarf-on-Beckinsale action.

Note 1. There is in fact at least one recorded case where MZ twins developed as a boy and a girl, because one twin from an XY zygote lost its Y chromosome at an early cell division, and grew up as an XO female, while the other twin was a normal XY male. But this is exceedingly rare, and I'm sure it is not what the scriptwriter had in mind.

Note 2. According to an interview, Naveen Andrews 'grew up in Wandsworth [London] with his brother and parents, Nirmala and Stanley, who moved from Kerala [South India] to London after their arranged marriage in 1965.' If 'Andrews' is their original family name, this suggests that his parents are Anglo-Indians in the sense of being from a community of mixed British and Indian ancestry. In the 19th century it was common for the lower ranks of the British military and commercial classes in India to marry Indian women, who would convert to Christianity. Their offspring could not easily marry either British or Indian partners, and therefore became a distinct endogamous community, with occupations mainly in the railways and public services. Anglo-Indians in this sense should be distinguished from the offspring of mixed Anglo-Indian marriages in Britain today. There is also an older usage of 'Anglo-Indian', used to describe the higher levels of British society in India under the Raj. In this sense the term is analogous to 'Anglo-Irish', and does not imply any Indian ancestry. Intermarriage at the higher levels of society was rare after the 18th century. This old usage can cause misunderstanding when people like Rudyard Kipling or Augustus De Morgan, whose ancestry was entirely European, are described as 'Anglo-Indian'.

Note 3. In principle one dwarf parent might be heterozygous for a dominant condition, such as achondroplasia, while the other is homozygous for a different recesssive condition. An offspring (like McConaughey) might then be a non-dwarf but carry one recessive dwarf gene. But in this case there would no additional risk to his children unless his partner also carried the recessive gene, which is highly unlikely.