The Nucleus Flashcards
What are the only eukaryotic cells that contain no nucleus?
Mature RBCs and sieve cells
What kind of cell have more than one nucleus?
Polynuclear WBCs
What organelle acts as the nucleus in prokaryotes?
The nucleoid
Where is the prokaryote genome found?
On a single, usually circular chromosome
Where is the eukaryote genome found?
On several linear chromosomes
What are the two forms in which chromatin exists in?
Euchromatin and heterochromatin
What is the difference between euchromatin and heterochromatin?
Euchromatin is available for transcription; heterochromatin is not (also condensed)
What is a nucleosome?
The fundamental subunit of chromatin. Each nucleosome consists of DNA wrapped around a histone octamer
Where are the parts of DNA strands that code for rRNA found?
The nucleolus
Where are genes for ribosomes transcribed?
The nucleolus
Where is the site for ribosome assembly?
The nucleolus
What happens to the nuclear envelope during cell division?
It dissipates so the chromosomes can be bound by cytoskeleton
What is the function of nuclear pores?
Controls the traffic of cell contents between the cytoplasm and nucleus
How big are nuclear pores and how big can the expand to?
10nm; can expand to 25nm
What size of molecules are allowed free passage through the nuclear pores?
Ones with low molecular weight ie less than 60kDa
