Question

Which of the following is a type of regulation of gene expression unique to eukaryotes? a. attenuation b. use of alternate \(\sigma\) factor c. chemical modification of histones d. alarmones

Short answer

c. chemical modification of histones

Step-by-step solution

Identify the Question

The question asks for a type of regulation of gene expression that is unique to eukaryotes.

Review the Options

Consider each given option: a. attenuation b. use of alternate \( \sigma \) factor c. chemical modification of histones d. alarmones

Understand Each Regulation Type

Research or recall knowledge about each type:a. Attenuation: A regulatory mechanism in prokaryotes.b. Use of alternate \( \sigma \) factors: Common in prokaryotes.c. Chemical modification of histones: Involves modifications like acetylation and methylation that affect chromatin structure in eukaryotes.d. Alarmones: Signaling molecules in prokaryotes.

Identify the Unique Regulation Type

Chemical modification of histones involves eukaryotic-specific processes such as chromatin remodeling, which regulate gene expression uniquely in eukaryotic cells.

Conclude with the Correct Answer

The correct option is c. chemical modification of histones.

Key concepts

Chromatin Remodeling

In eukaryotic cells, the DNA is tightly packed with proteins into a structure called chromatin. For genes to be expressed, the chromatin must be restructured to make certain regions accessible for transcription machinery. This process is known as chromatin remodeling. The process involves repositioning or altering the density of nucleosomes (the basic units of chromatin, consisting of DNA wrapped around histone proteins). This repositioning allows or restricts access to specific genes.
Chromatin remodeling is essential because it helps in:

• Turning genes on or off
• Facilitating repair of damaged DNA
• Allowing the cell to respond to environmental changes

In summary, chromatin remodeling is a way to dynamically control which parts of the genome are active at any one time.

Histone Modification

Histones are proteins around which DNA is wrapped to form nucleosomes. Modifying these histones is a key mechanism for regulating gene expression in eukaryotic cells. Chemical modifications like acetylation, methylation, phosphorylation, and ubiquitination can occur on the histone tails, impacting how tightly or loosely DNA is wound.
Some common types of histone modifications include:

• **Acetylation:** Addition of acetyl groups, usually leading to an open chromatin structure and active gene expression.
• **Methylation:** Addition of methyl groups, which can either activate or repress gene expression depending on the specific sites and context.
• **Phosphorylation:** Addition of phosphate groups, often linked to responses like DNA damage repair.

These modifications work as signals to recruit other proteins that either promote or repress transcription, thereby affecting gene expression.
In essence, histone modifications provide a layer of regulation, fine-tuning the accessibility of DNA to the transcription machinery.

Eukaryotic Cells

Eukaryotic cells are complex cells that contain a nucleus and other membrane-bound organelles like mitochondria, endoplasmic reticulum, and Golgi apparatus. They are markedly different from prokaryotic cells (bacteria and archaea), which do not have a nucleus or membrane-bound organelles.
Some key features of eukaryotic cells include:

• **Nucleus:** Encloses the cell's genetic material (DNA).
• **Organelles:** Specialized structures that perform various functions (e.g., energy production, protein folding, waste removal).
• **Cytoskeleton:** Provides structural support and facilitates movement of materials within the cell.

Because of their structural complexity, eukaryotic cells have more sophisticated mechanisms for regulating gene expression, including chromatin remodeling and histone modifications.
This complexity allows these cells to perform specialized functions, adapt to different environments, and respond to various signals, contributing to the diversity and functionality of multicellular organisms.