Question

Which of the following is a difference between the solenoid and zigzag models for the formation of the 30 nm filament? a) The solenoid model involves zigzagging of DNA, while the zigzag model involves coiling of DNA. b) The solenoid model is a more compact structure compared to the zigzag model. c) The solenoid model involves direct binding of histone H1 to DNA, while the zigzag model does not. d) The zigzag model is the correct representation of the 30 nm filament, while the solenoid model is outdated.

Answer 1

The solenoid model is characterized by tight helical turns of DNA around histones for a compact structure, whereas the zigzag model features a less compact structure with a zigzag arrangement of nucleosomes.

Step-by-step explanation:

The main difference between the solenoid and zigzag models for the formation of the 30 nm filament is that the solenoid model involves DNA wrapped in tight helical turns around a core of histones, creating a more compact structure. The zigzag model, on the other hand, suggests a less compact structure where nucleosomes are arranged in a zigzag pattern, with the linker DNA entering and exiting at various points, and it emphasizes the role of histone H1 in facilitating the formation of a more extended zigzag fiber. It's important to note that neither of these models involves the other's characteristic coiling or zigzagging exclusively—the difference mainly lies in the arrangement of nucleosomes and the degree of compaction they confer to chromatin.

Answer 2

The accurate statement among the given options is:

b) The solenoid model is a more compact structure compared to the zigzag model.

Let's analyze the differences between the solenoid and zigzag models for the formation of the 30 nm filament:

Step 1: Understand the solenoid model and the zigzag model:

- Solenoid Model: The solenoid model suggests that the 30 nm filament is formed by a tight helical winding of the nucleosome chain. It envisions the DNA wrapped around histone octamers in a coiled and compact manner.

- Zigzag Model: The zigzag model proposes that the nucleosome chain forms a less compact, zigzagging structure with DNA wrapping around histone octamers in a less tightly coiled fashion.

Step 2: Identify the differences:

a) The solenoid model involves zigzagging of DNA, while the zigzag model involves coiling of DNA.

- This statement is not accurate. The solenoid model does not involve zigzagging of DNA; it actually suggests a tight coiling. The zigzag model, on the other hand, suggests a less compact, zigzagging structure.

b) The solenoid model is a more compact structure compared to the zigzag model.

- This statement is accurate. The solenoid model proposes a more tightly coiled and compact structure, whereas the zigzag model suggests a less compact, more extended structure.

c) The solenoid model involves direct binding of histone H1 to DNA, while the zigzag model does not.

- This statement is not entirely accurate. Both the solenoid and zigzag models consider the presence of histone H1 in the formation of the 30 nm filament. However, the details of histone H1 binding may vary between the two models.

d) The zigzag model is the correct representation of the 30 nm filament, while the solenoid model is outdated.

- This statement is not necessarily true. The correct representation of the 30 nm filament is still a subject of debate in the field of molecular biology. Both the solenoid and zigzag models have been proposed and are still under investigation. Neither model can be definitively labeled as correct or outdated at this time.