Studied by 0 people
Looks like no one added any tags here yet for you.
What is the nucleus?
Contains the genetic material of DNA within a double membrane
Continuous with the ER
Supported by fibrous nuclear lamina
Nucleus is compartmentalized
Had nucleolus (ribosome assembly site)
What is the nucleolus?
Site of ribsome assembly in nucleus
Prokaryotes don’t have nuclei. What does that tell us about their DNA?
There might be some organized nuclear-type region, but it isn’t surround by a membrane.
What’s special about the nucleus membrane?
It is a single membrane folded back on itself!
What is the nuclear lamina?
It is a meshwork of proteins called lamins.
What are nuclear pores?
Allows the movement of material between the cytoplasm and the nucleus!
Consists of about nuceloporins (30 different proteins)
What can diffuse through nuclear pores?
Small ions and molecules (<5 kilodaltons) can diffuse freely
Smaller than 60 kilodaltons can still diffuse but SLOWLY
Large molecules can use active transport
DNA is divided into a set of…
chromosomes (very long strand of DNA)!
What is chromatin?
DNA in a complex with proteins and RNA molecules.
Purpose is to package DNA into more dense/compact structures.
Highly dynamic structure that changes to regulate gene expression, DNA replication, and cell division.
What is the basic unit of chromatin?
Nucelosome
What is a nucleosome?
Length of DNA wrapped around a core of histone proteins
Looks like beads on a string when stretched out.
What is linker DNA?
Between the “beads”, a short stretch of DNA (~80 nucelotides)
Repeats every 200 nucleotides
How is DNA chopped up during cell death?
In fragments of 200 nucleotides; whenever linker DNA is
What happens to chromatin during interphase?
The chromatin is condensed into a fiber that is 30 nm in diameter.
What determines the formatting of the 30 nm fiber?
Interactions between the N-terminal tails of histones in neighboring nucleosomes.
What is linker histone H1?
Binds to the outside of each nucleosome to help condense the chromatin
What is heterochromatin?
Highly condensed chromatin that is SILENCED (cannot be expressed); includes telomeres and centromeres
What is euchromatin?
Less condensed chromatin that can be EXPRESSED and transcribed by RNA
What regulates chromatin sturctures?
Covalent modifications to the histones tails!
What is lysine acetylation?
Neutralizes the positive charge on lysine!
What is lysine methylation?
Masks the charge; doesn’t eliminate it but does make its effects more subtle
What is serine phosphorylation?
Makes histone more negative!
What is replication origin?
A site where DNA duplication is initiated!
What is a centromere?
A site of attachment to the mitotic spindles!
What is a telomere?
Prevents the ends of chromosomes from being mistaken for broken DNA.
Note 
Flashcard (51)