Males of most animal species die earlier than females because their smaller Y chromosome is unable to protect an unhealthy X chromosome, research suggests.
Once genetic lesions for diseases such as cystic fibrosis and haemophilia were identified, the idea of replacing or correcting defective genes grew into what we now call "gene therapy".
Humans, and even pet dogs, are more than just products of genes. As Russell Bonduriansky writes, environments play a vital role in shaping us – even before conception.
