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DNA Chromatin and Chromosomes
Medical School Biochem
29
Biochemistry
Graduate
08/20/2011

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Cards

Term
What is the Philadelphia Chromosome?
Definition
Modified chromosome 22 (22 has a BCR). Mechanism: translocation of ABL gene to BCR site of 22. Clinical consequences: unregulated ABL resulting in acute leukemia
Term
What is a BCR?
Definition
Break control region in a chromosome. Area with a high potential to break
Term
How many base pairs per turn of B-DNA?
Definition
10 bp per turn
Term
The strands of DNA are ________
Definition
antiparallel
Term
What is the difference in Hydrogen bonding in nucleotides, and why is this significant?
Definition
A forms 2H bonds with T
and
C forms 3H bonds with G

Implications: CG rich strands will require higher temp to denature

High replication activity on AT rich regions (often ORI tend to appear there)

low activity in regions rich with CG
Term
How is DNA packaged in Eukaryotic organisms? Prokaryotic?
Definition
Eukaryotic DNA is packaged in a nucleus

Prokaryotic DNA: no nucleus, linear or circular DNA
Term
What is the distinguishing characteristic of A form DNA?
Definition
11 bp per turn as opposed to the 10 bp per turn of classic B-DNA
Term
What are the characteristics of Z-form DNA?
Definition
-left handed helix
-rich in CG islands
-higher tendency to break
Term
What is negative supercoiling? What enzyme causes it to happen?
Definition
Enzyme: Topoisomerase II (DNA Gyrase)

Negative supercoiling is the action of putting coils in a circular (bacterial) DNA. This serves 2 functions. 1. Storage. 2.When the DNA is unzipped by helicase positive supercoiling is less of an issue.

Clinical correlation: drugs like Cipro inhibit DNA Gyrase action and cause cell apoptosis
Term
[image]
Identify the structure
Definition
Deoxyribose
Term
[image]
Identify the structure
Definition
Ribose
Term
[image]
Identify the structures
Definition
1. Minor Groove of DNA
2. Major Groove of DNA
Term
What is Heterochromatin?
Definition
very highly condensed and packed (like the centromere and telomere of DNA)

High Me covalent modification of histones

Tends to silence genes
Term
What is Euchromatin?
Definition
Highly active sites for gene expression

Genes are less compressed

high Ac of histone site
Term
What is the ORI? How is it different for human cells compared to bacterial cells?
Definition
ORI: Origin of Replication of DNA

Tend to be AT rich site on the chromosome

Humans have multiple ORI sites while Bacteria tend to have one.
Term
Typical Human somatic cells contain __ pairs of chromosomes?
Definition
23 pairs, for a total of 46 chromosomes
Term
What are aneuploidies?
Definition
Variations from normal chromosomal count within a cell
Term
Sickle Cell Anemia is caused by a point mutation of what gene?
Definition
HBB gene which is on chromosome 11

11p15.5
Term
What is a centromere?
Definition
Site on chromosome for mitotic spindle attachment
Term
What is the structure and function of nucleosomes?
Definition
Structure

octomeric core nucleosome
(H2A,H2B,H3,H4)2

H1 serves as connection between linker DNA while the nucleosome core is used to wrap DNA segments (~200 nucleotides)
Term
How many nucleotides per nucleosome?
Definition
~200
Term
What is the significance of the histone fold?
Definition
The histone fold allows histones to "handshake" this makes the formation of the nucleosome core more energetically favorable
Term
Nucleosome bind with DNA along the?
Definition
Major Groove
Term
What enzyme catalyzes Histone acetylation?
Definition
HAT
Histone acetlytransferase
Term
What enzyme catalyzes Histone deacetylation?
Definition
HDAC
Histone deacetylase
Term
What enzyme catalyses Histone methylation?
Definition
Slides: Hmet
Histone Methylase?

Wikipedia: HMT
Histone methyltransferase
Term
What enzyme catalyzes Histone demethylation?
Definition
Hdemethylase

2 families
Term
What is the function of insulator DNA?
Definition
organizes coding DNA into loops for easier replication
Term
What is the laminum?
Definition
Laminum are the proteins of the nucleus.

Clinical correlation: Laminopathies can cause rapid aging in children
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