Question

The system of rope-like fibers that give shape and stability to the nucleus is made up of proteins called: The system of rope-like fibers that give shape and stability to the nucleus is made up of proteins called:________. a. importins. b. exportins. c. lamins. d. euchromatin. e. heterochromatin.

Answer 1

C. lamins.

Explanation:

1. Lamins: are filamentous proteins which forms a mesh-like layer inner side the nuclear membrane of animal cells.

2. Lamins have many functions inside the nucleus like; i) it provide mechanical support for the nucleus, ii) it regulate DNA replication and transcription and iii) it organizing chromatin.

3. In mammals, two major A-type lamins named as lamin A and lamin C and two major B-type lamins named lamin B1 and lamin B2, have been characterized.

Answer 2

(c) is the correct option

Step-by-step explanation:

• Lamins are nuclear intermediate filaments that make a meshwork of filaments at the nuclear periphery
• Each major lamin isoform forms a separate meshwork
• Lamins possess a tripartite structure with a central α-helical rod flanked by a short head and a longer tail domain
• They assemble into a meshwork of 10 nm filaments with distinct cross connections
• Lamins have been divided into A and B types, which differ in their expression patterns, biochemical characteristics, and behavior during mitosis
• Lamin A and its smaller splice variant lamin C, which lacks 74 carboxyterminal amino acids and become solubilized during mitosis and are only expressed in terminally differentiated cells
• B lamins are present in all metazoan cells and remain associated with the nuclear membrane throughout development and differentiation The carboxyterminus of lamins, with the exception of mammalian lamin C, undergoes post-translational modifications