Nucleus

Question 1

Size and structure

Answer 1

Largest organelle, surround by nuclear envelope, contain genetic info of cell (DNA + RNA)

Question 2

Genetic info

Answer 2

DNA arranged as chromosomes

Coil around histone core

Question 3

Nucleoproteins

Answer 3

+ve histones: control uncoiling/expression of genes, modified to promote/suppress gene expression
Non-histone proteins: enzymes for synthesis RNA/DNA and other regulatory proteins

Question 4

Nuclear envelope

Answer 4

2 lipid bilayers w/ intermembranous space between, contains nuclear pores, regulate exchange of metabolites, macromolecules, ribosomal subunits (communication between nucleus and cytoplasm)
Defines eukaryotes

Question 5

Nucleolus

Answer 5

Site of rRNA and ribosome assembly

Question 6

Nuclear functions

Answer 6

Gene replication/repair, transcription, ribosome production, protect DNA
Control centre of cell

Question 7

Heterochromatin

Answer 7

Electron dense areas
Tightly coiled, inactive chromatin
Constitutive = condensed throughout cell cycle/development, highly repetitive sequences not transcribed, role in chromosome structure
Facultative = regions of euchromatin convert to heterochromatin, potential for gene expression, condensed or loosen depending on cell type

Question 8

Barr body

Answer 8

Inactive X chromosome in female somatic cells to regulate amount X-linked gene product transcribed
Facultative heterochromatin

Question 9

Euchromatin

Answer 9

Electron lucent areas

Active DNA, act as template for RNA synthesis