Nucleus

Question 1

Structure of nucleus

Answer 1

Nuclear envelope (2 membranes), which is supported by nuclear lamina. along the membrane are nuclearporins, which form the nuclear pore complex. Within the nucleus is DNA, and ribosomal DNA is concentrated in the nucleolus

Question 2

Nuclear lamina

Answer 2

Made of intermediate filaments ( lamin in humans). Provides support and connection points for DNA organization

Question 3

Nucleus function

Answer 3

Store DNA, regulate gene expression, produce RNA and ribosomal sub-units, and controls DNA duplication

Question 4

Nuclear pore complex structure

Answer 4

Made of nucleoporin rosettes, which form channels in the nuclear envelope (the 2 layers fuse at the rosettes).

Question 5

Nucleo-cytoplasmic exchange

Answer 5

mRNA, tRNA, and ribosomal sub-units leave the nucleus, control signals, building materials, and energy enter.

Question 6

Nucleolus

Answer 6

Concentrated region in nucleus that makes ribosomal RNA and ribosomal sub- units. (Assembled in the cytoplasm)

Question 7

How is DNA arranged?

Answer 7

DNA interacts with H2-H4 histones to make 10nm fibers with ‘beads’ (nucleosomes ) -these further interact with H1 histones to form 30nm fiber, which loops to form 300nm fiber, and finally coils during cell division into metaphase chromosomes. If not in chromosomes, they are still specially organized with sister pairs generally separated.

Question 8

Euchromatin

Answer 8

Lighter region - less rightly packed, so DNA is accessible and can be used by the cell

Question 9

Heterochromatin

Answer 9

Dark region- tightly packed and holds genes not currently in use