The Nucleus

Question 1

What are the functions of the nucleus?

Answer 1

Storage of DNA, genetic template.

Question 2

What are the benefits of compartmentalised genetic material in eukaryotes?

Answer 2

It protects the DNA, increases the surface area for membrane-localised reactions, increases efficiency of transcription and synthesis and it allows more ways to regulate gene expression.

Question 3

What is the endoplasmic reticulum?

Answer 3

It is the site of protein production by ribosomes, protein folding and glycosylation (adding sugar molecules).

Question 4

What does lamina mean?

Answer 4

A thin plate.

Question 5

What are the properties of the nuclear lamina?

Answer 5

It is related to intermediate filaments, it forms a meshwork on the inner nuclear membrane and associates with DNA (functional) and

Question 6

What is a LINC complex?

Answer 6

Protein complexes that link the nuclear lamina with the cytoskeleton.

Question 7

What do nesprins do?

Answer 7

They connect to different cytoskeleton elements.

Question 8

What does PLF stand for?

Answer 8

Pore-linked filaments.

Question 9

What does Titin do?

Answer 9

It binds chromosomes and lamina.

Question 10

What does NuMa stand for?

Answer 10

Nuclear mitotic apparatus.

Question 11

What is nuclear actin?

Answer 11

Short filaments or monomeric (G-actin).

Question 12

What are chromosomes?

Answer 12

DNA-protein complexes that are specially packaged for cell division.

Question 13

What is chromatin?

Answer 13

A complex of DNA, RNA and proteins.

Question 14

What is Euchromatin?

Answer 14

True chromatin that is less visible by microscopy. It is not so densely packed and makes up the majority of the genome and is localised in central part of the nucleus.

Question 15

What is heterochromatin?

Answer 15

Different chromatin that looks dark under the microscope. It is tightly packed condensed DNA. It is localised around the lamina and nucleoli.

Question 16

What are the different types of RNA?

Answer 16

mRNA, rRNA, tRNA.

Question 17

What substances are used to import proteins from the cytoplasm?

Answer 17

RNA polymerase, ribosomal proteins, transcription factors and all other structural proteins.

Question 18

What is the nuclear pore complex?

Answer 18

Ring structure with 8-fold symmetry, 30 nuclear pore proteins and has a central channel filled with FG+-Nups that form selective barriers to transport.

Question 19

What are the two kinds of movement through the NPC?

Answer 19

Passive transport and facilitated transport.

Question 20

What does passive transport involve?

Answer 20

Small molecules and proteins.

Question 21

What does facilitated transport involve?

Answer 21

RNAs, larger proteins, macromolecular complexes.

Question 22

What are the energy sources required for facilitated transport?

Answer 22

ATP hydrolysis for mRNA, GTP hydrolysis for proteins, tRNA and ribosomes.

Question 23

What is mRNP?

Answer 23

mRNA-protein complex.

Question 24

What happens in the mRNA export processing complex?

Answer 24

It includes processing, capping, splicing proteins as well as export factors.

Question 25

How does mRNP go out or into the nucleus?

Answer 25

Through nuclear pore complexes.

Question 26

What is required for mRNP to leave the nucleus?

Answer 26

ATP hydrolysis - it releases Dbp5 in the cytoplasm and mRNP remodelling.

Question 27

What are importins?

Answer 27

Nuclear transport receptors.

Question 28

What do importins do?

Answer 28

They bind to cargo proteins in the cytoplasm and interact with FG_Nups and release cargos in the nucleus.

Question 29

What enables cargo release?

Answer 29

It is enabled by Ran-GTP binding to importin-beta. This causes a conformational change that results in the complex coming apart.