NASA’s Simulated Mars Mission Marks 200 Days Inside Habitat

Every time a cell divides, it must copy its DNA with extraordinary precision. But this process is constantly challenged by DNA damage. Among the most dangerous lesions are DNA interstrand crosslinks (ICLs), which chemically bind the two strands of DNA together and block the machinery responsible for copying the genome.

Shapes of beaks and snouts come in an extraordinary range of forms, reflecting adaptations to different lifestyles and environments. Yet beneath this diversity lies a paradox: across birds and mammals, faces are built using deeply conserved developmental programs. So how does evolution generate such striking differences without reinventing the underlying machinery?