Besides the nucleus, certain cell organelles contain their own DNA. Which combination of organelles listed below correctly includes organelles with their own genetic material?

Introduction / Context:
In eukaryotic cells, the nucleus is the main storehouse of genetic material. However, certain organelles also contain their own small DNA molecules and can synthesise some of their own proteins. This feature is central to the endosymbiotic theory, which explains the origin of these organelles. Exam questions often ask students to identify which organelles, aside from the nucleus, have their own DNA. This question focuses on choosing the correct pair of such organelles.

Given Data / Assumptions:

• The question discusses organelles that contain DNA in addition to the nucleus.
• The options list various combinations of common organelles: chloroplasts, mitochondria, nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, and lysosomes.
• We assume eukaryotic cells, such as plant and animal cells, not prokaryotic cells.
• We also assume standard textbook information about organelle structure and function.

Concept / Approach:
Two organelles in eukaryotic cells are well known for containing their own DNA: mitochondria and chloroplasts. Mitochondria are the powerhouses of the cell, responsible for aerobic respiration, and they possess circular DNA similar to bacterial DNA. Chloroplasts, found in plant cells and some protists, carry out photosynthesis and also contain their own DNA. Ribosomes, Golgi apparatus, lysosomes, and endoplasmic reticulum do not contain DNA; instead, they rely on nuclear and organelle DNA for instructions. Therefore, the correct answer must be the pair that consists entirely of organelles known to have their own genetic material, which is chloroplasts and mitochondria.

Step-by-Step Solution:
Step 1: Recall that mitochondria contain their own circular DNA and can make some of their own proteins. Step 2: Remember that chloroplasts in plants and algae also contain DNA and have a semi autonomous genetic system. Step 3: Examine the options and identify which pair includes both chloroplasts and mitochondria together. Step 4: Note that option A lists chloroplasts and mitochondria, both of which are known to contain DNA. Step 5: Confirm that ribosomes, endoplasmic reticulum, Golgi apparatus, and lysosomes do not have their own DNA molecules.

Verification / Alternative check:
The endosymbiotic theory proposes that mitochondria and chloroplasts originated from free living bacteria that entered ancestral eukaryotic cells and formed a symbiotic relationship. Evidence for this includes the presence of their own DNA, their bacterial like ribosomes, and their ability to replicate independently of the nucleus. No such origin story or DNA presence is described for ribosomes or other membrane bound organelles like the endoplasmic reticulum. This widely accepted theory and supporting data confirm that mitochondria and chloroplasts are the organelles with their own DNA.

Why Other Options Are Wrong:
Option B: Nucleus and ribosomes is misleading because although the nucleus has DNA, ribosomes do not contain DNA; they are composed primarily of rRNA and proteins. Option C: Ribosomes and mitochondria includes one correct organelle (mitochondria) but wrongly pairs it with ribosomes, which lack DNA. Option D: Endoplasmic reticulum and nucleus again mixes a DNA containing structure (nucleus) with an organelle that does not have its own DNA. Option E: Golgi apparatus and lysosomes are involved in processing and digestion within the cell but do not possess their own DNA.

Common Pitfalls:
Students sometimes assume that any complex organelle may contain DNA or confuse RNA rich structures like ribosomes with DNA containing organelles. Another common mistake is to forget that the question is specifically about organelles with their own DNA, not just structures associated with genetic information. To avoid confusion, it is useful to remember the simple trio of DNA locations in eukaryotic cells: nucleus, mitochondria, and, in plants and algae, chloroplasts. Focusing on this list helps quickly eliminate incorrect combinations in multiple choice questions.

Final Answer:
The correct combination of organelles that contain their own DNA is chloroplasts and mitochondria.