Cell nucleus Flashcards
What is the function of the nucleus? [5 marks]
- Storage of DNA
- DNA replication
- Transcription
- Ribosomal biogenesis
- Control communication between the nucleoplasm and the cytoplasm
What is the function of the telomere? [1 mark]
Protect chromosome ends
What is the function of the centromere? [1 mark]
Needed during cell division
G dark chromosomes [4 marks]
- Heterochromatin
- Near centromeres and telomeres
- Highly condensed
- Form 10% of genome
G light chromosomes [4 marks]
- Euchromatin rich
- Active genes
- Loosely condensed
- Form 90% of genome
Metacentric chromosome structure [1 mark]
P and Q arm are of simiilar length
Submetacentric chromosome structure [2 marks]
- Centromere is towards one end
- Longer Q arm
Acrocentric chromosome structure [2 marks]
- P arm is short
- P arm contains repetitive DNA and ribosomal RNA gene
Chromosome organisation in metaphase [1 mark]
Condensed
Chromosome organisation in interphase [1 mark]
Decondensed
Chromosome territories function [2 marks]
- Store DNA
- Control access to DNA
Chromosome territories structure [2 marks]
- Separate chromosome arms and bands
- Non-overlapping domains in the interphase nucleus
Where are gene poor chromosomes located in the nucleus? [1 mark]
The peripheral parts
Where are gene rich chromosomes located in the nucleus? [1 mark]
The interior
Examples of nuclear compartments [5 marks]
- Promyelocytic leukaemia (PML) nuclear bodies
- Spliceosomes
- Nucleoli (making ribosomes)
- Nascent RNA
Zones of nucleolus [3 marks]
- Fibrillar - rRNA genes
- Dense fibrillar - rRNA transcripts
- Granular - processing and assembly
Why does the cell need so many copies of the rRNA genes?
The rRNAs are not translated so there aren’t polysomes forming
How many nuclear pore complexes does the mammalian nuclear envelope have? [1 mark]
3000 to 4000
What leaves the nucleus and what allows that to occur? [3 marks]
- Ribosomal subunits
- mRNA
- requires nuclear export signal
What enters the nucleus and what allows that to occur? [4 marks]
- Histones
- DNA/RNA polymerases
- Nuclear proteins
- Needs a nuclear localisation sequence
