You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Gene

Context:
Housekeeping genes are critical for carrying out basic cell functions and so are expressed at a relatively constant level (constitutively). Since their expression is constant, housekeeping genes are used as experimental controls when analysing gene expression. Not all essential genes are housekeeping genes since some essential genes are developmentally regulated or expressed at certain times during the organism's life cycle.

Question:
What type of genes are necessary for performing basic cell functions?

Housekeeping genes