Your 60 second guide to ‘three-parent’ babies…

The Westminster parliament will discuss ‘mitochondrial transfer’ or ‘three-parent’ babies today. Concerns about the ethics and safety of this have been raised. If parliament agrees, such procedures will become legal in the UK. There has already been considerable discussion and debate about this, as Polly Toynbee describes.

The problems seem to centre around the mitochondrial DNA (mtDNA), and confusion of this with the DNA which we inherit from both our parents.

A chicken’s egg is a cell; the yolk is the nucleus, which is contained by a membrane. The white of the egg is the cytoplasm, again contained by a membrane. The nucleus holds the genetic material which makes individuals unique. Within the cytoplasm are a number of ‘machines’. One such ‘machine’ is the mitochondrion. All our cells, except red blood cells, contain varying numbers of mitochondria.

Mitochondria are the ‘power houses’ of the cell; technically, they ‘respire’, that is use oxygen in a series of chemical reactions to produce energy. Mitochondria have their own DNA, quite separate from the DNA in the nucleus.

Mitochondria have DNA similarities to bacteria, and it’s thought that they represent bacteria which were captured, during evolution, by primitive cells—a process called symbiogenesis. (Symbiosis is the name given to two organisms which live together, and ‘support’ each other. Lichens are an example of symbiosis.)

Occasionally, mitochondria are damaged, for example by mutation, and do not function properly. Infants born with such defective mitochondria then have a range of diseases.

The concept behind mitochondrial transfer is to replace the diseased mitochondria with healthy ones.

Our mitochondria all came from our mothers, and their mothers before them. The sperm does not contribute to mitochondria in the fertilised ovum. (The mitochondria in the sperm are destroyed or ‘lysed’ at fertilisation.)

So, mitochondria are in the ovum. It’s not technically feasible to remove diseased ones from a prospective parent’s ova. Instead, this is what is proposed.

A donor ovum is necessary, one with healthy mitochondria. The nucleus of this cell is removed, and replaced with the nucleus from the ovum of a prospective mother. The ovum is then fertilised as in a conventional ‘test-tube’ baby, and then implanted into the womb.

Alternatively, the donor ovum may already be fertilised, and this fertilised nucleus is removed, and replaced with a fertilised ovum. This BBC link has a couple of diagrams to explain the process; it includes some of the surrounding discussion.

Although we are told that this will be a world first, the BBC reports that there were 50 or more such mitochondrial transfers some years ago in the US.

Our inherited characteristics come from out parents, with their DNA, their chromosomes ‘combining’ to form us. mtDNA pays no part in our characteristics (unless the mitochondria are diseased). Any suggestion that mitochondrial transfer or replacement is the start of something that will produce ‘designer babies’ is totally mistaken and totally without foundation.

  • notimetoshine

    Its a fascinating and amazing process. I hope silly ideologies and lack of scientific knowledge dont hold this up.

  • Korhomme

    After a fairly short debate, the House of Commons, on a free vote, approved the changes to the regulations concerning this.

    I watched part of the debate; the problems seemed to be about 1) ethics, 2) safety, and 3) parliamentary procedure. Some of the ‘antis’ didn’t really seem to understand what it was all about, conflating nuclear DNA with mtDNA into the ‘total genome’.

  • Brian Walker

    Religious reservations no doubt played their usual part, bringing
    Protestant and Catholic together.

    Alliance’s Naomi Long was the only Northern Ireland MP to vote in favour. Noes were DUP MPs McCrea and Shannon who both spoke and Wilson, SDLP MPs Durkan and Ritchie, independent MP Sylvia Hermon.
    Nigel Dodds, Ian Paisley, David Simpson and Alasdair McDonnell were absent from the debate.

    Dr McCrea asked:

    “In her opening speech the Minister mentioned that the
    devolved Administrations had been kept abreast of these proposals. I wanted to
    intervene to ask her whether the regulations will apply in Northern Ireland if
    they are passed in this House. That is an important question to which an answer
    is needed.”

    He got no answer but the governing HFEA Act 1990 under which these
    regulations were made does apply to NI.

  • notimetoshine

    I can understand the DUP no votes, after all science isn’t exactly that parties strong point. But i would have expected better from the SDLP MPs. Just as well stuff like this isn’t devolved.

  • Granni Trixie

    In the abstract, I could easily be swayed by ‘slippery slope’, ‘GM babies’ talk (legitimate ethical concerns I believe) where it not that like many I have come up close and personal to one of the conditions (muscular dystrophy) likely to benefit from this research intervention. What I want to emphasise however is that in considering this issue we must factor in the impact not only the individual child but on parents, siblings and close family. They have to manage the knowledge that a beloved child or sibling is not going to live beyond their teens (and I know of a family who have three children with MD). There is also cross generational impact on mental health from knowledge that boy grandchildren and greatgrandchildren can be born with the condition and the girls carriers.
    I see ethical questions around is it right to test interventions to try to address serious medical conditions as a bit like those around moral questions around homosexuality or abortion – you can argue in the abstract all you like but actual experience of the reality almost forces you to seek more nuanced positions or solutions rather than an absolute position.