The nuclear substance composed of histone proteins and DNA is:
a. Chromatin
b. The nucleolus
c. Nucleoplasm
d. Nuclear pores

Verified step by step guidance

1. Understand the components of the cell nucleus: The nucleus contains DNA, proteins, nucleolus, nucleoplasm, and nuclear pores, each with distinct functions.
2. Recall that DNA in the nucleus is wrapped around proteins called histones to form a complex substance that helps organize and compact the DNA.
3. Identify that this complex of DNA and histone proteins is known as chromatin, which is the material that makes up chromosomes during cell division.
4. Recognize that the nucleolus is a dense region within the nucleus involved in ribosomal RNA synthesis, not the DNA-protein complex.
5. Note that nucleoplasm is the fluid inside the nucleus, and nuclear pores are openings in the nuclear envelope, so neither refers to the DNA-histone complex.

Key Concepts

Chromatin

Chromatin is the complex of DNA and histone proteins found in the nucleus of eukaryotic cells. It packages DNA into a compact, organized structure, allowing efficient regulation of gene expression and DNA replication.

Histone Proteins

Histones are positively charged proteins around which DNA winds to form nucleosomes, the basic units of chromatin. They play a key role in DNA packaging and gene regulation by controlling access to genetic information.

Nuclear Components

The nucleus contains several components: nucleoplasm (the fluid matrix), nucleolus (site of ribosome synthesis), and nuclear pores (channels for molecular transport). Understanding these helps distinguish chromatin from other nuclear structures.