This ‘junk’ gene may be important in embryo development

Mice — and maybe humans — can’t get past the two-cell stage without it

LINE-1 gene

LINE-1 DANCE  RNA copies of a jumping gene called LINE-1 (red) are mass produced in mouse embryos at the two-cell stage of development (shown). DNA is shown in blue and cells’ outer boundaries are drawn in orange in this microscope image. 

M. Percharde et al/Cell 2018

A once-maligned genetic parasite may actually be essential for survival.