Signed, Sealed, Delivered

Those millions of couples going through the agony of infertility seize on every bit of news in the field, knowing that each piece of information increases the chances they will yet hold a baby in their arms. Now, three scientists have honed in on a miraculous finding that will change all we know about the process of human fertilization. Scientists from Bradford and Leeds universities have revealed that sperm has a specific type of DNA signature that acts as a key toward unlocking the egg's fertility, leading to new human life.

Same Species

Dr. Martin Brinkworth of the University of Bradford, along with Dr. David Miller and Dr. David Iles of the University of Leeds found that sperm produces a type of DNA code that can be read only by an egg of the same species. In order to unlock the potential of the sperm, the egg has to correctly parse this "script." But this DNA signature does more than just enable fertilization. Scientists feel that this script may help explain how a species produces its unique genetic identity.

Dr. Iles explains, "What we have discovered is a previously unrecognized DNA packaging 'signature' in mammalian sperm that may be essential for successful fertilization of the egg and development of the embryo. We think it may also be ancient in origin."

Plausible Explanation

Researchers posit that the "lock and key" mechanism they discovered may also serve to explain why healthy human males sometimes produce infertile sperm. "Up until now, Doctors have struggled to understand idiopathic male infertility. Our latest research offers a plausible explanation for why some sperm malfunction or fail to function correctly," comments Dr. Miller.

If we wish to understand how this DNA signature is implicated in male infertility, it is helpful to imagine that the length of the strand of DNA that is contained within the sperm cell is longer than a meter. The DNA must be wound tight in order to fit into the teeny space at the head of the sperm cell. But Leeds researchers found that human and mouse DNA are not always packaged the same way.

Sometimes the father's DNA is packaged in a compact fashion, at other times in a looser fashion. The researchers posit that when DNA is packed more loosely, it is more vulnerable to toxins in the environment that can affect its potency. Such toxins might include anti-cancer drugs, or cigarette smoke. Dr. Brinkworth comments, "This might mean that anything capable of causing genetic damage to sperm could have particular significance for the development of the embryo."

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