Prokaryotic cells, which lack a nucleus, divide by a different process called binary fission. Mitosis varies between organisms. For example, animal cells undergo an open mitosis, where the nuclear envelope breaks down before the chromosomes separate, whereas fungi undergo a closed mitosis, where chromosomes divide within an intact cell nucleus.
Bilateral renal agenesis is a condition in which both kidneys of a fetus fail to develop during gestation. It is one causative agent of Potter sequence. This absence of kidneys causes oligohydramnios, a deficiency of amniotic fluid in a pregnant woman, which can place extra pressure on the developing baby and cause further malformations.
This clinical scenario may present no signs or symptoms and the kidneys may function normally. It is associated at times with Mullerian dysgenesis. Variations of renal ectopia and fusion: A) Pelvic kidney open arrow, B) subdiaphragmatic/thoracic kidney, C) crossed fused ectopic kidney, and D) horseshoe kidney.