Lec 2. Chromosomes & Genomes Flashcards
What are telomeres?
The ends of linear chromosomes
What are the Origins of replication?
Where the replication bubble starts
What do centromeres do?
Connects sister chromatids
True or False? Telomeres & Centromeres are Eukaryote specific.
True
What two categories does repetitive DNA contain?
Highly repetitive and Middle repetitive.
What falls under highly repetitive?
Satellite DNA
What falls under Middle repetitive?
Tandem repeats & Interspersed Retrotransposons
What falls under Tandem repeats?
Micro-satellites, Mini-satellites, and Multiple copy genes
What falls under interspersed retrotransposons?
SINEs and LINEs
What is an example of multiple copy genes?
rRNA genes
What is an example of Mini-satellites?
VNTRs
What is an example of Micro-satellites?
STRs
What is an example of SINEs?
Alu
What is an example of LINEs?
L1
What are retrotransposons?
Middle repetitive, relics from past virus integrations. Some can cut and paste at will.
What are SINEs?
Retrotransposons that are short
What are LINEs?
Retrotransposons that are long
What is one of the driving forces of evolution?
Gene duplication. Tandem repeats
What is the fastest way to produce ribosomes?
To have multiple copies of rRNA genes.
What are VNTRs and STRs used for?
DNA fingerprinting
What are VNTRs and STRs?
Tandem repeats. Mini-satellites and Micro-satellites. Dispersed randomly in genome. Can cause disease, Huntingtons, Fragile X.
What is Satellite DNA?
High repetitive. Found in regions of heterochromatin. Can be transcribed during development.
How does a genome that is small and circular get compacted?
Supercoiling
How does a genome that is large and linear get compacted?
Winding it around histones to form nucleosomes.
What is the DNA packaging order?
DNA-Nucleosomes-Chromatin-Chromatin loops-Decondensed Chromatin loops-Chromosome.
What is Chromatin?
Slightly or moderately compacted DNA found during interphase/G1 cell cycle.
What does DNA exist as after S-phase?
Sister chromatids
True or False? Chromosomes are not compacted during mitosis
False. Chromosomes are very compacted.
What are the two structures of chromatin?
Heterochromatin & Euchromatin
What is the appearance of Heterochromatin?
Compacted
What is the appearance of Euchromatin?
Uncoiled
What is the activity of Heterochromatin?
repressed
What is the activity of Euchromatin?
Active.
What is the Histone Density for Heterochromatin?
Higher
What is the histone Density for Euchromatin?
Lower
Where is Heterochromatin located in the chromosome?
Telomeres,centromeres, and other repetitive regions.
Where is Euchromatin located in the chromosome?
Coding DNA regions.
What genes does Heterochromatin contain?
No genes or repressed genes.
What genes does Euchromatin contain?
Actively expressed genes.
When does Heterochromatin replicate?
Later in S phase.
When does Euchromatin replicate?
Earlier in S phase.
True or False? Chromosomes are spatially separated in the eukaryotic cell nucleas
True.
True or False? Just because chromosomes are compacted does not mean they arnt in the nucleus.
True. For example A Barr Body.
What is A Barr Body?
inactivated (all heterochromatin)X-chromosome. Located in nucleus.
How are nucleosomes held together?
By the attraction between +charged amino acids (Arg, Lys) and -charged sugar-PO4 backbone
What is the directionality of proteins?
N terminus to C terminus.
Where on the nucleosome are prime sites for modification?
Histone tails
During modifications, Lysines can be
Acetylated and or methylated
During modifications, Arginines can be
Methylated.
During modifications, Serines can be
Phosphorylated
What are writers?
Proteins that ADD histone markers
What are Erasers?
Proteins that remove histone markers.
What is an example of an Acetyl writer?
HAT (acetyltransferase)
What is an example of an Acetyl Eraser?
HDAC (deacetylase)
What is an example of a Methyl writer?
HMT (methyl transferase)
What is an example of a Methyl eraser?
HDM (demethylase)
What is an example of a Phosphate writer?
Kinase
What is an example of a Phosphate eraser?
Phosphatase
What is an example of a Ubiquitin writer?
Ubiquitin Ligase (U3)
What is an example of a Ubiquitin eraser?
DUB (Deubiquitinating Enzyme)
What are readers?
Proteins that recognize histone marks
What does Acetylation do?
Activates
What does Methylation do?
Inhibits.
What does Phosphorylation and uqiquitination do?
Either increase or decrease histone density on DNA
What stops heterochromatin formation?
A Barrier (insulator) sequence in DNA
What three mechanism can a barrier protein act by?
Tethering, sheltering and re-writing.
What does tethering do?
Creates a physical roadblock
What does sheltering do?
Shelters euchromatin from view of heterochromatin.
What does re-writing do?
Re-writing marks reverse heterochromatin
What is epigenetics?
Genetic change without mutation
True or False? Histone marks are not heritable
False. Histone marks are heritable
True or False? DNA can be methylated and/or acetylated just like histones
True.
What are some examples that result from changes in DNA methylation?
Imprinting disorders, cancer
What is the C-value paradox?
DNA content does not relate to body complexity.