Gender

Gender is a deprecated feature which can be found in some less evolved species in this universe.

An example of a place where it still exists in some birth-class and inferior-class species is the planet known as Earth with the humans being an example of a specie which has it. There are three known genders: male, female and hermaphrodite, although the third one is not so well known. For a gendered species to reproduce, a male and female of that species is needed to create a baby, whereas more up-to-date species can reproduce using technology. Even more advanced species and reproduce by making copies of themselves.

There are set gender identities assigned to male and female, although it is possible for someone to be born with a different gender identity than their assumed biological one. In some cases, there is a lack of a gender identity and others may have their gender identity sitting in the middle of the male and female genders.

Changes
Beings capable of altering the source of objects are perfectly capable of changing the gender of an individual using this method as the bodies of many species tend to have the source set on the body as a whole as opposed to on individual atoms in said body until, the body dies with the decomposition occuring where the source starts to break down into a simpler form which is replicated across all the atoms.

By changing the variable for gender in the source of the individual, the change propagates across all of the body including constructs such a DNA and the overall structure of the body which entirely depends on the gender differences of that specific specie.

Removal of gender
Humans are perfectly capable of upgrading to a more up-to-date system, but they're not doing so due to ethical problems they have.