When using a type 2 topoisomerase, explain the function of the "g-segment" of DNA.
The g-segment is held in place at the DNA binding domain of the enzyme.
What does the "g" stand for in "g-segment."
"G" stands for "gate," indicating that this is the point at which the DNA will be broken.
When using a type 2 topoisomerase, explain the function of the "t-segment" of DNA.
The t-segment triggers the closing of the two ATP binding domains around it, trapping it in place.
What does the "t" stand for in "t-segment."
"T" stands for "transport," indicating that it is the segment of DNA that will pass through the "gate."
________ discovered that X-rays cause mutations.
Henry Muller.
__________ discovered that heat extracts of virulent S. pneumoniae could make nonvirulent S. pneumoniae virulent.
Frederick Griffith.
What gene determined virulence in S. pneumoniae?
A smooth cell wall - indicating the presence of a capsule.
What is the process by which bacteria pick up extracellular DNA and incorporate it into their own?
Transformation.
Who concluded that the "transforming factor" is DNA, not protein or RNA? How?
Maclyn McCarty.
It was destroyed by DNase, but not protease (trypsin) or RNase.
Who used radioactive tracers to show that DNA is the genetic component of bacteriophages?
Alfred Hershey and Martha Chase.
What were the tracers used by Hershey and Chase?
35S for proteins and 32P for nucleic acids.
In DNA, what is Euchromatin?
"True," active genes that are expressed.
In DNA, what is heterochromatin?
Genes at telomeres and centromeres - not expressed.
True or False?
Bacterial chromosomes are more compact that Human chromosomes.
True.
Bacteria chromosomes = 1,000 genes / Mb
Baker's yeast = 500 genes / Mb
Drosophila = 80 genes / Mb
Homo sapiens = 9.3 genes / Mb
What is a particle containing a defined ratio of DNA and protein?
That is, two coils of DNA wrapped around a protein spool.
A nucleosome.
What is a protein that binds DNA non-specifically and acts as the protein spool in a nucleosome?
A Histone.
What is the term for "a series of protein containing structures on a string of DNA"?
Chromatin.
How many subunits make up the core of a histone? They are primarily (Beta strands / alpha helices).
Eight - an octamer.
Alpha Helices.
There are ______ types of subunits in the histone. There are _____ copies of each for ______ total subunits. Each subunit has _____ amino-terminal tail.
1.) 4
2.) 2
3.) 8
4.) 1
True or False?
Any DNA sequence can be wrapped around a nucleosome?
True.
Histone-DNA spooling is non-specific. The interactions only exist between the protein sidechains and the phosphate backbone, not the base pairs.
Histone # _____ is outside of core and binds linker DNA between nucleosomes.
Histone # 1.
How many base pairs of DNA make two tight wraps around the octamer core?
140 base pairs.
The wraps contribute (positive / negative) supercoils to the DNA.
Negative.
Human DNA exists in negative supercoils.
The N-terminal tails of the subunits of a histone serve what function?
They determine how the chromatin packs together.
Chromatin is ____ nm in diameter, and coils into a filament of _____ nm.
1.) 10 nm
2.) 30 nm
Which diameter of chromatin is ideal for transcription processes?
10 nm.
Starting from a strand of DNA, list the order (8 steps) in which the DNA packs into a chromosome ready for mitosis.
1.) DNA
2.) 10 nm chromatin
3.) 30 nm filament
4.) Filament loops
5.) Rosettes (of 6 loops)
6.) Coils (of 30 rosettes)
7.) 1 Chromatid (of about 10 coils)
8.) Sister chromatids
True or False?
Histones are non-specific and therefore exist in only one state.
False.
Modifications to histone tails make slight changes to their function.
A methylated arginine on a histone tail has what effect? An acetylated lysine?
