Cell Biology Multiple Choice Questions on “Nucleus – Structure and Function”.
1. Nucleoporins are __________
A. Nuclear pores
B. Ribosomes on nuclear membranes
C. rRNAs in the nucleolus
D. None of the mentioned
Answer: A
Clarification: The nuclear membrane is a double-layered membrane that is interrupted in places by the nuclear pores. The nuclear pores provide channels for the transport of molecules such as water, proteins, RNAs etc. The nuclear pores are collectively known as Nucleoporins.
2. The transport factors that help in the transport of molecules through the nuclear pores are known as ___________
A. Nucleopherins
B. Nucleoporins
C. Karyopherins
D. Karyoporins
Answer: C
Clarification: Proteins, ribosomal subunits, and some DNAs are transported through the pore complexes mediated by a family of transport factors known as karyopherins. Karyopherins are of two types- those that mediate movement of molecules into the nucleus are called importins and those that mediate movement out of the nucleus are called exportins.
3. Lamin proteins that bind to the intra-nuclear chromatin are _____________
A. Emerin
B. Nesprin
C. LEM-3
D. Cannot be said
Answer: C
Clarification: The nuclear lamina is mostly composed of lamin proteins. The cytosolic lamin proteins which face the cytoplasm, such as Emerin and Nesprin binds to the cytoskeleton to provide structural rigidity. Lamins such as LEM3 are found inside nucleus and form the nucleoplasmic veil and bind to the intra-nuclear chromatin.
4. Nuclear Organizer Regions (NOR) is found in ________
A. Nuclear matrix
B. Nucleolus
C. Nuclear lamina
D. Nucleoporins
Answer: B
Clarification: The nucleolus is a dense granular region present inside the nucleus. It is concerned with the production of rRNA and consists of tandems of rDNAs, DNA that codes for rRNA. These rDNA rich regions of nucleolus is called Nuclear Organizer Regions (NOR).
5. Cajal bodies mainly consist of the protein _________
A. Emerin
B. Actin
C. Coilin
D. Desprin
Answer: C
Clarification: Cajal bodies re sub-nuclear compact structures with diameter between 0.2-2.0 micrometers, depending on the species. Under electron microscope, the appear as small tangles threads with a dense dictricution of the Coilin protein. They are bound to the nucleolus by coilin proteins.
6. Which of the following is not a function of Cajal bodies?
A. snRNP biogenesis
B. histone mRNA processing
C. telomere assembly
D. tRNA processing
Answer: D
Clarification: Cajal bodies re sub-nuclear compact structures with diameter between 0.2-2.0 micrometers, depending on the species. They are mainly related to RNA synthesis and helps in RNA-related metabolic processes such as snRNPs biogenesis, maturation and recycling, histone mRNA processing and telomere maintenance.
7. Which of the following is also known as Kremer bodies?
A. Cajal bodies
B. PML bodies
C. Nuclear speckles
D. Nucleolus
Answer: B
Clarification: Promyelocytic leukaemia bodies (PML bodies) are spherical bodies that are found scattered throughout the nucleoplasm and are around 0.1–1.0 µm. They are also known by a number of different names such as nuclear domain 10 (ND10), Kremer bodies, PML oncogenic domains and also nuclear dots.
8. Which of the following plays a role in oncogenic function?
A. Kremer bodies
B. Cajal bodies
C. Splicing speckles
D. None of the mentioned