Question

which discovery supported the endosymbiotic theory?
dna in mitochondria
dna in the cell nucleus
dna in ribosomes
dna in the cytoplasm

Explanation:

The endosymbiotic theory proposes that mitochondria (and chloroplasts) were once free - living prokaryotes that were engulfed by a larger cell. One of the key pieces of evidence for this theory is that mitochondria have their own DNA. This is similar to the DNA of prokaryotes. The DNA in the cell nucleus is part of the eukaryotic cell's own genetic material and not relevant to the endosymbiotic theory. Ribosomes do not have DNA. And while there can be some DNA - containing organelles in the cytoplasm (like mitochondria), the general "DNA in the cytoplasm" is too vague compared to the specific "DNA in mitochondria" which is a well - known support for the endosymbiotic theory.

Answer:

DNA in mitochondria.