• Question: Does the sperm of a male get "smarter" with age? Meaning, is there more information passed to offspring? I ask, because of that study, on mice, that demonstrated a fear stimulus, being passed on to offspring, with "no" changes in DNA.

    Asked by deepgreendesign to Rachael, Penny, Jennifer, Jean-Paul, David, Dave on 7 Jan 2014.
    • Photo: David Christensen

      David Christensen answered on 7 Jan 2014:

      That’s a great question that I’m not sure has an answer yet.

      I hadn’t actually heard of this study before, so thanks for introducing me to it, it’s really interesting. From my understanding, it seems that a fear of a particular odour was passed down from a father to an offspring (although some people contest that a fear was actually passed and further work is being done to confirm this). At the moment, it seems that many scientists are sceptical and want to see a mechanism for how this “fear” could be passed in the sperm. The most likely explanation would be, broadly speaking, epigenetics.

      I don’t know what you know about epigenetics so I’ll give a quick analogy to explain it. All of our cells have a script in the form of our entire genome. Epigenetics works like a highlighter so that the cells know which is their part and which lines belong to other cells, so that they only do what they are supposed to do. It seems epigenetics can also highlight certain bits of information in the genome that is passed to offspring.

      As an example, scientists have found that a woman’s diet while pregnant can affect the lifetime health of her child through epigenetic highlighting to change their risk of developing diseases such as diabetes. In fact, because a woman’s eggs develop in the developing embryo, epigenetic effects can be passed from a pregnant woman into the eggs that will become her grandchildren.

      Therefore, I guess it is similarly possible that sperm will carry different information depending on the environment they are produced in (i.e. whether there is a lot of food, not much food or some other variables). In the case of the fear being passed on in mice, at the moment scientists aren’t sure how a brain impulse to associate fear with a particular odour can be transmitted to an epigenetic change in the sperm, so they aren’t completely sure that this fear is being passed on. Other types of information could be passed on more easily, but I wouldn’t describe the sperm as getting smarter because their epigenetics are influenced by their immediate environmental signals and aren’t being learned over a longer period of time.

      I hope this makes sense and answers your question. Which was a great question by the way and really interesting for me to read up about!

      Sorry, I just realised I wrote a seriously long answer!