W2 Nucleus

Question 1

Functions

Answer 1

Store/maintain cell’s DNA  
DNA replication
Transcription
Ribosomal biogenesis
Controls communication b/een nucleoplasm + cytoplasm

Question 2

Karyotyping

Answer 2

Test that evaluates number + structure of CSs to detect abnormalities

Spectral karyotyping - allows visualization of all human CS at one time by “painting” each pair of CS in a different fluorescent colour

Question 3

Heterochromatin

Answer 3

Gene poor (periphery of nucleus)
Near centromeres + telomeres
Associated w/nuclear envelope (often)
10% genome = heterochromatin

Question 4

Euchromatin

Answer 4

Location for active genes
Less condensed
Majority of genome

Question 5

Nucleolus

Answer 5

Largest substructure in nucleus
Transcription rRNA genes to produce large 45S rRNA precursor
Cleavage/modification of rRNA into 18S, 5.8S + 28S rRNA
Assembly of 18S (Small) + 5.8S, 28S, 5S (large)

Question 6

Acrocentric CS

Answer 6

Centromere located near one end, humans normally have 5 pairs

200 rRNA gene copies per haploid genome - located in tandem copies on these type of CSs

Question 7

Nuclear envelope

Answer 7

2 lipid bilayers
Communication b/een nucleoplasm/cytoplasm via nuclear pore
Nuclear envelope in mammalian cells around 3000-4000 nuclear pore complexes

Question 8

Nuclear pore

Answer 8

Only small water soluble molecules can diffuse freely through pore
Large = AT
RS + mRNA proteins require nuclear export signal
Nuclear proteins require nuclear localisation sequence (AA sequence that tags protein for import into cell nucleus by nuclear transport)

Question 9

Why no internal membranes

Answer 9

Sub nuclear compartments exist despite the absence of internal membranes

CS territories: store DNA + control access to DNA
Replication factories: nascent DNA production
Transcription factories (contain RNA PII, template DNA strand + newly synthesised mRNA): nascent RNA production
Spliceosome: irregular domains containing splicing factors
Nucleoli: RS biogenesis
PML nuclear bodies: possible nuclear depot + recruit unrelated proteins

Question 10

Nuclei lamela

Answer 10

Lines nuclear envelope + maintains structure → NL proteins involved in gene expression