In a typical animal cell, which organelle (other than the nucleus) contains its own DNA and is therefore partly genetically independent?

Introduction / Context:
Eukaryotic cells contain many different organelles, each specialised for particular functions. Most genetic material is stored in the cell nucleus, but some organelles also carry their own small amount of DNA. Knowing which organelles have their own DNA helps in understanding cell evolution and energy production. This question asks which organelle, other than the nucleus, contains DNA in a typical animal cell.

Given Data / Assumptions:

• The context is a typical animal cell.
• Options given are centriole, Golgi apparatus, lysosomes, mitochondria, and endoplasmic reticulum.
• We assume basic knowledge of cell structure and organelle functions.
• We focus on the presence of organelle specific DNA.

Concept / Approach:
Mitochondria are double membrane bound organelles responsible for aerobic respiration and ATP production. They contain their own circular DNA and ribosomes, which is evidence for the endosymbiotic theory of their origin. This mitochondrial DNA encodes some of the proteins used by the mitochondrion. In contrast, centrioles, Golgi apparatus, lysosomes, and the endoplasmic reticulum do not possess their own DNA; they rely entirely on nuclear DNA for their protein components. Therefore, mitochondria are the correct answer for an animal cell organelle containing DNA besides the nucleus.

Step-by-Step Solution:
Step 1: Recall that the nucleus is the main storehouse of DNA in eukaryotic cells. Step 2: Remember that mitochondria have their own small circular DNA and can synthesise some of their own proteins. Step 3: Consider centriole, which is involved in cell division organisation but does not have its own DNA. Step 4: Recognise that the Golgi apparatus modifies and packages proteins but relies on nuclear DNA for its protein components. Step 5: Lysosomes contain digestive enzymes but no independent genetic material. Step 6: The endoplasmic reticulum is a membrane system for synthesis and transport; it does not possess its own DNA. Step 7: Therefore, mitochondria are the only listed organelles in a typical animal cell that contain DNA apart from the nucleus.

Verification / Alternative check:
Cell biology references consistently describe mitochondria as semi autonomous organelles because they contain DNA and ribosomes and can replicate independently inside the cell. This is regarded as evidence that mitochondria evolved from ancient bacteria engulfed by early eukaryotic cells. In animals, chloroplasts are absent, so mitochondria are the main extra nuclear DNA containing organelles. The other listed organelles are not described as having their own genomes, which verifies that mitochondria are the correct choice.

Why Other Options Are Wrong:
Centriole: A cylindrical structure involved in spindle formation but does not contain its own DNA. Golgi apparatus: Functions in packaging and secretion of proteins and lipids, without its own genetic material. Lysosomes: Membrane bound vesicles with hydrolytic enzymes, derived from the Golgi apparatus, and lacking independent DNA. Endoplasmic reticulum: A network of membranes for protein and lipid synthesis, but dependent entirely on nuclear DNA.

Common Pitfalls:
Some learners may generalise that all major organelles contain some DNA, which is not correct. Others may remember that chloroplasts also contain DNA and confuse plant versus animal cells. To avoid mistakes, remember that in animal cells, mitochondria are the primary organelles besides the nucleus that carry DNA.

Final Answer:
The correct answer is Mitochondria.