DNA is not present in

A. Nucleus

B. Mitochondria

C. Chloroplast

D. Ribosomes

To determine where DNA is not present among the options provided, let's analyze each one carefully. The question asks us to identify the cellular component that lacks DNA. Here’s a breakdown of each option:

Nucleus

The nucleus is often referred to as the control center of the cell. It houses the cell's genetic material, which is organized into chromosomes. In eukaryotic cells, the nucleus contains the majority of the cell's DNA, making it a crucial component for genetic information storage and regulation.

Mitochondria

Mitochondria are known as the powerhouses of the cell because they generate energy through the process of cellular respiration. Interestingly, mitochondria have their own circular DNA, which is distinct from the nuclear DNA. This DNA is involved in coding for some of the proteins necessary for mitochondrial function.

Chloroplast

Chloroplasts are the organelles responsible for photosynthesis in plant cells. Similar to mitochondria, chloroplasts also contain their own DNA, which is involved in the synthesis of proteins necessary for their function in converting sunlight into energy.

Ribosomes

Ribosomes are the cellular machinery responsible for protein synthesis. They are composed of ribosomal RNA (rRNA) and proteins, but they do not contain DNA. Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum, but they do not have any genetic material of their own.

Final Analysis

Based on the information above, the correct answer to the question is Ribosomes. Unlike the nucleus, mitochondria, and chloroplasts, which all contain DNA, ribosomes do not have any DNA associated with them. They play a vital role in translating messenger RNA (mRNA) into proteins, but they do not store or contain genetic information.