Question

What two properties, one structural and one functional, distinguish heterochromatin from euchromatin?

Short answer

Heterochromatin is a highly condensed region of chromatin and thus is not accessible to the cell's transcription machinery for gene expression. On the other hand, euchromatin is a less condensed region of chromatin and thus accessible to the cell's transcription machinery, thereby leading to gene expression.

Step-by-step solution

Gene Expression

The genetic information coded in the DNA (Deoxyribonucleic acid) molecule is transcribed to form mRNA (messenger ribonucleic acid). The mRNA molecule is further translated to form proteins. This flow of information from DNA to proteins is known as gene expression.

Genes, the unit of heredity, are present in the DNA molecule. The genes are expressed during gene expression to synthesize proteins.

Chromatin

The DNA in the cells is associated with proteins to form chromatin. The chromatin in eukaryotic cells is highly compacted. However, the compaction level is not uniform during the interphase of the cell cycle.

In the interphase, some chromatin regions are tightly packed, and these regions are called heterochromatin. Other areas of the chromatin that is less compactly packed are called euchromatin.

Distinction between heterochromatin and euchromatin

Heterochromatin is a highly condensed region of the chromosomes. On the other hand, euchromatin is a less condensed region of the chromosome. This is one structural difference between heterochromatin and euchromatin.

One functional difference between heterochromatin and euchromatin is that the former is transcriptionally inactive, and the latter is transcriptionally active. Due to the highly condensed regions of heterochromatin, the genes are not accessible by the transcription machinery of the cell.

As a result, genes cannot be transcribed by the cell. On the other hand, the genes on the euchromatin region are accessible to the transcription machinery due to its less compact region. As a result, the genes are transcribed by the cell and leads to gene expression.