General Exam IV Qs Flashcards
What is the defining organelle of euks?
(and what it contain?)
The nucleus!
Contains genomic DNA
What is the role of the nucelus?
Stores and protects genetic information, regulated expression, maintains it and so forth
-also forces spatial and temporal separation of transcription and translation
Bacterial gene expression:
what happen go!
(bonus for how different from euks)
-purple chain mRNA
-RNA polymerse main circle
-ribosome second big circle (ribosome will attach and start transcbing)
-growing peptide
9 RNA polymerases
-blobs at top are ribosomes and peptides theyre producing
-transcriptiona nd translation happening at same time messenger RNA is being synthesized
dear god do see the slide Unit III pg 4
Gene expression in a euk cell:
Transcription and
Translation: __________
and ___________
separated”
Transcription and
Translation: spatially
and temporally
separated”
For Gene expression in euks, what occurs in the nucleus and what occurs in the cytoplasm?
Transcription and Processing occur in the nucleus
Translation occurs in the cytoplasm
Describe transcription in euks
(where happen, and what make?)
Occurs in Nucleus
makes pre-mRNA (bacs dont do this)
Describe Processing (in gene transcription) in euks
(where happen, and what make?)
in nucleus,
makes mRNA,
mRNA reads
5’-cap
5’ (backwards G)———- 3’ (poly A tail, added by polyA polymerse, As not encoded in DNA)
Protein looks for those 3 backwards Gs
Both must be there to help them become mRNA
There are sections of exons in the sequence, and introns
The introns then gotta be removed (splicing)
So then exons are joined together to form coding sequence
5’ cap
-poly A tail
-removal of introns (all three happening at same time)
**do see slide Unit III pg 5
Are exons or introns removed before the remaining join together to form the coding sequence?
(bonus for the name of this event)
The introns then gotta be removed (splicing)
So then exons are joined together to form coding sequence
Describe Translation in euks
(where happen and what is synthesized?)
Occur in cytoplasm
Translation -> proteins synthesized!
DNA scattered through nucleus, there’s a nucleolus, area of intense transcription activity
-nucleoolis appears as large stain, due high trsanscription to ribosomal proteins
(do review slide for visual, unit III pg 5)
What is the nucleolus?
(do what and look like what on microscope slide?)
area of intense transcription activity
-appears as large stain, due high transcription to ribosomal proteins
How does a euk nucleus package its DNA?
(bonus for how bacs do it)
Use of histone protein complexes
forms a histone octomer (2 units each)
one additional histone
-bacs use (something omg sorry I forgot!) cations!
Histone proteins form an _________
octomer
Histone proteins form an octomer,
how many times does DNA wrap around this octomer, what is this called, and what attracts DNA to the octomer?
A lot of positively charged amino acids
-DNA naturally attracted
-DNA is wrapped around octomer to form nucleosome (wraps twice)
Name for histone octomer/DNA complex?
Nucleosome
How many bps of DNA make direct contact with the histone proteins (core)?
~160 base pairs of DNA make direct contact with the histone proteins (core)
Name of histones, and which one is unique?
(how many form the main octomer complex?)
H2A-
H2B-
H3-
H4-
H1- special, not in the main complex, binds at the conjunction where one strand comes in/out to twist a little bit
Nucleosome:
What is this?
and ~how many bps will one form?
basic unit of DNA packaging
-About every 200 base pairs, another nucleosome will form
Why do all this histone business?
-All done to make DNA shorter, you gotta make it shorter
What’s special about H1 histone protein?
(hint: histone not in the complex)
Histone H1 binds at the conjunction where one strand comes in/out to twist a little bit
“11nm fiber”
the 11nm fiber is kinda first stage of supercoiling of DNA (after nucelosome complexes of histone proteins and DNA form), later forms the 30 nm fiber
What little structure enables formed nucleosomes to reach out and coil together tightly?
(bonus: forming the what?)
-There’s a little tail protein branching out from the nucleosomes so they can interact with each other and pull tighter forming the 11nm fiber
Unit III pg 7
Why called 11nm fiber?
the diameter of the fiber structure formed by the coiling and packing of nucleosomes in the process of DNA compaction. It be one of the early stages in the hierarchical organization of DNA
11 nm fiber then compacts further to form the _______
30 nm fiber,
11nm fibers associate with each other and coil up together to from the 30 nm fiber (diameter)
Then protein scaffold formed to make look like WWWWWWW (sorta, review slides
Unit III pg 7
Finally, 30 nm fiber is condensed to what structure?
Packing ratio how many times shorter?
Eventually that loop gets fully packaged down to mitotic chromosome,
packing ratio ~8,000x shorter