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50 Genetics Ideas You Really Need To Know -

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50 Genetics Ideas You Really Need To Know

Genetics is a very young science. It's just over 50 years since Watson and Crick mapped the
structure of DNA. Only recently has the human genome been available. Mark Henderson traces the
history of the science, describes some of the paradoxes and tackles a number of highly charged
topics under than banner, 'Nature versus nurture'.

Transcript

Robyn Williams: So, genes for kindness, genes for blushing, genes for empathy even. And there's a
book now on genetics that covers it all 50 Genetics Ideas You Really Need to Know by Mark Henderson
of The Times of London.

Mark Henderson: What I really thought I wanted to do was to give a sense of the history of genetics
and the fact that it is a very, very young science. It's only just over 50 years since Watson and
Crick mapped the structure of DNA. Then also to explore some of the issues that genetics raises,
and then finally to try to update people on some of the really exciting discoveries that are
emerging in the field right now. In the past five years we've learned a phenomenal amount about the
human genome, and that's really where the book ends up.

Robyn Williams: It's in fact just over 100 years since Gregor Mendel's work came out, he was doing
it but it was hidden. So 1901, that's about 110 years, so going even back to classical genetics
it's quite a young science.

Mark Henderson: It is indeed, yes, and of course it's instructive as well to remember Darwin in all
of this because while Darwin didn't know of genetics and didn't know of Mendel's work, the two
great theories of evolution and genetics meshed together perfectly, and that something that was
done in the early 20th century in the era of classical genetics, people like Morgan and Muller were
able to marry up those two theories and show that genetics was the mechanism by which evolution
worked. Of course we're celebrating Darwin's bicentenary this year, so it's a good time to be
thinking about genetics.

Robyn Williams: Okay, let's take an example from that because one of the arguments about whether we
actually came from the apes was that the apes have 24 sets of chromosomes and we've only got 23,
and yet if you look into the chromosomes themselves there's a wonderful telltale clue on chromosome
2 that lets us know that the relationship is in fact there. What is it?

Mark Henderson: This is true. It was actually thought for a long time that we had 24 pairs of
chromosomes as well, until better counting techniques came along and we were able to tell we had
23. Chromosome 2, it turns out, is actually a fused chromosome from two smaller ones. So where the
apes have 24 we have 23 because two of them have actually joined together. That, if you like, could
be the chromosome that makes us human.

Robyn Williams: And the wonderful thing is that in the middle you've got one of these telomeres,
these shoelace things that Elizabeth Blackburn, the Australian, has worked on so well. So there is
a beautiful piece of science that yet again confirms some of the ideas. Moving on, you mentioned
DNA fingerprinting and Alec Jeffreys. We couldn't have CSI, we couldn't have forensic science half
the time without some of the contributions he's made. What is this marvellous DNA fingerprinting?

Mark Henderson: DNA fingerprinting involves the fact that everybody's genetic code is individual to
them, and as a result of that, by collecting samples, you can actually tell whether a sample found
at a crime scene comes from an individual. The popularity of shows like CSI with regard to genetic
fingerprinting actually is that sometimes people think it's more reliable than it actually is.

Robyn Williams: Some people have said that you could actually tell someone's surname from looking
at the fingerprint, you know, there is a Henderson DNA.

Mark Henderson: Well, there's probably a Henderson Y chromosome, that's certainly the case, because
the Y chromosome is passed down in exactly the same way as surnames, through the patrilineal line.
So I have my father's Y chromosome, he has his father's Y chromosome and so on back to the year
dot. In fact there's a famous study that's included in the book about the Cohanim, a group of Jews
who claim to be able to trace their ancestry back to the high priest Aaron, Moses' brother in the
Bible. And actually when scientists went along and tried to test the Y chromosomes of people who
claimed they were Cohanim, it came out that an awful lot of them did actually share the same Y
chromosome type. So it's interesting sometimes how social traditions like that are also being
partially confirmed by DNA evidence.

Robyn Williams: Mark, are our Y chromosomes really in trouble, 'crumbling', as you put it in the
book?

Mark Henderson: Well, 'crumbling'...that's not my term so much as Bryan Sykes', the Oxford
geneticist. The Y chromosome is small and weedy compared to the X, it contains very, very few
genes, and there are hypotheses that it is on the way out because unlike the other chromosomes it
never has a partner so it can't recombine, and that's one of the key processes by which chromosomes
remain healthy, they swap material with each other.

However, the problem with the idea of a Y chromosome dying out is that it's absolutely critical to
sex. We are, by default, all female, and it's a single gene on the Y chromosome, the SRY gene,
which actually kicks the cascade of masculinisation into action in the womb. Were the Y chromosome
actually to start losing the SRY gene, any organism that lacked that would of course itself be
infertile, would be incapable of fathering children, and therefore that's the biggest anti-adaptive
force that you can have in evolutionary terms. So evolution shouldn't really actually ultimately
allow the Y chromosome to die out.

Robyn Williams: One thing I love about the book is it's a wonderful update. For those who've got a
vague idea of what's happening in genetics you can look at a particular section and get a
bite-sized summary of the particular view in 2009, 2010 of what people are thinking. For instance,
what about the 'gay gene'? I remember Dean Hamer crashing through at the American Association for
the Advancement of Science a few years ago and saying 'we've got it!' It wasn't quite true, was it.

Mark Henderson: Not really. Dean Hamer found a region on the X chromosome that appeared to be
strongly linked to homosexuality, but that work unfortunately has not been replicated. Nobody else
has been able to find that. Indeed, there's no gene yet known that is reliably linked to
homosexuality, but that doesn't mean that there's no genetic role in homosexuality because an awful
lot of other work...first of all, twin studies which compare identical twins to non-identical
twins. Identical twins of course share all their DNA, non-identical twins only half of it. An
identical twin who is gay, his twin is more likely to be gay than fraternal twins are. So when you
compare twins like that you can actually estimate the heritability of a trait like homosexuality,
for example, without actually knowing anything about the genes.

There's also some very interesting work that's been done by an Italian team, a chap called Andrea
Camperio-Ciani from the University of Padua, and what he's done is looked at the evolutionary
paradox of homosexuality. Obviously if you're homosexual you are, on average, generally speaking
going to have less children. Of course there have been plenty of homosexuals who have had children
in the past, but it's not the most adaptive way forward in a Darwinian sense, and that's always
been a big paradox. If there's some evolutionary basis for homosexuality, if it is biological, how
has it actually survived, because natural selection is really brutal with things that even slightly
reduce your reproductive fitness.

What he's actually looked at and found some quite compelling evidence for is there may be some gene
that we don't know about or probably a combination of lots of genes that promote homosexuality when
they're in a man but when they're in a woman promote fecundity, fertility. So while a gay man who
has this gene may have fewer children, his sisters, his mother, his female cousins, his daughters
if he has any, will actually be more fertile. So that gene can still find its way through, even
though it's deleterious in reproductive terms, not in social terms necessarily at all, to the
person who carries it.

Robyn Williams: You've got Dolly the sheep on the cover, a very nice cover actually. On the gossip
front, Ian Wilmut, who you mention in this book, had a bit of a bumpy 2008 because he got a
knighthood and various people said he shouldn't have got it. What's the state of play on that?

Mark Henderson: It has kind of died down. This is one of the things that happens in science. Ian
Wilmut was very much credited as the main creator of Dolly the sheep, along with Keith Campbell,
because they were the guys who led the team, they were the senior scientists at the top of that
group. The person who actually did the transfer of the DNA into the nucleated egg to actually clone
Dolly wasn't either of them, it was a laboratory technician in the team who feels he hasn't been
credited quite the way that he should be. And Wilmut, to be fair, has admitted that, he's says that
'I wasn't the guy who actually did the cloning' but very often the people who lead the team have a
really critical role. They're the intellectual inspirations, even if they don't actually do the
physical experiments themselves. It's an aspect of how science works really.

Robyn Williams: At the AAAS meeting where I often see you, this year in Chicago, there was the
ultimate press conference and session saying that we could actually manufacture genes. In other
words, as Craig Venter actually said, making a kind of DNA set of genes from scratch. Sydney
Brenner, who actually got the Nobel Prize for this sort of work, said it couldn't be done because
it's got to form naturally in a living thing. What's your view on whether they can stich a new
organism from scratch?

Mark Henderson: There are a large number of teams who are actually working on it. Craig Venter
himself is working on a slightly different project. What he's trying to do is stich together a
genome and then transfer it into a bacterium because while you may be able to recreate the genetic
code and stich that together, all the other stuff that goes on in the cell, the ribosomes et
cetera, all that architecture, we don't know how to build that from scratch at all. And so what
he's basically doing is trying to transplant this artificial genome that he's created into another
microbe that's had its genetic code removed. It's almost as if you were to take the software from
your computer and download it onto somebody else's computer, highjack it in that way.

But there are also some more innovative approaches. Some of the research we've heard about is
related to constructing new DNA bases even. So in the natural world we have four, there's A, C, G
and T, but this group here have produced eight other bases that just have a slightly different
chemical structure, and they've been able to get those to combine and to grow and even to evolve a
little bit in the lab. So I think this is very much a 'watch this space'.

Robyn Williams: And you can watch his space in the delightful book 50 Genetics Ideas You Really
Need to Know. Mark Henderson.