The Nucleus Flashcards
What is the first organelle to be discovered?
Nucleus
What is the nucleus?
Priciple defining charactersistic of eukaryotic cells.
What is the importance of the nucleus?
The nuclues seperates the process of transcription and translation, enables alternative splicing and associated complexity.
What does alternative splicing mean?
splicing of introns and combinations of extrons.
Where did the nucleas come from evolutionarily? Give both the hypothesis.
Hypothesis 1 - Invagination of membrane (inward folding)
Hypothesis 2 - Endosymbiotic
What is endosymbiosis?
Endosymbiosis is a theory suggesting that some organelles were free living bacteria which were enguled by a cell becoming combined with the cell.
Which of the hypothesis have implications for topology?
Both
How are DNA in the nucleus packaged?
They are packaged into chromosomes and are wrapped around histones for effecient packaging.
How are DNA packed in non - dividing cells?
Loosely packed forming a tangle of strands called chromatin.
How are chromatin organizations revealed?
EM staining techniques.
Whate are the stages of chromatin organization?
- Heterochromatin
- Euchromatin
- Nucleolus
What is heterochromatin?
Dense staining of interphase DNA.
What is Euchromatin?
Less - dense staining interphase DNA
What is Nucleolus chromatin staining organization?
Highly dense staining of RNA.
How are nucleus stained in colour?
Fluorescent in Situ hybridisation.
Is the nucleus compartmentalised?
Yes - chromosomes occupy specific territories within the nucleus, which may be identified by chromosomal painting
Territories are inherited but can change following differentiation or disease
How does the location of a gene change?
Depending on its transcriptional status.
How are the genes CD4 and centromeric heterochromatin identified?
Red stain for centromeric heterochromatin
Green stain for CD4.
What is CD4?
HIV receptor.
What has gene tagging proved?
Gene “tagging” together with improvements in microscopy have revealed the existence and
function of multiple sub-nuclear organelles in inter-chromatin space.
What are the adaptations of Nucleolus?
- Not membrane bound unlike other organelles
- It is a collection of macromolecules - rDNA genes, precursor rRNA, mature rRNA and more.
Give a function of nucleolus?
Site for processing ribosomal RNA to produce ribosomes.
Sub nuclear organelles(Finish)
What is the nuclear envelope?
Nuclear envelope is a double unit membrane perforated with pores and supported by a fibrous meshwork called the lamina
What is the lamina responsible for?
The lamina is responsible for ensuring the asymmetric nature of the double unit membrane.
