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What is one of the only cells in the body that lacks a Nucleus
Erythrocytes (Red blood cells)
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Define Chromatin
A complex of DNA, proteins, histones, and non-histone proteins in the nucleus of a eukaryotic cell
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Define Chromosome
Structure composed of a long DNA strand and associated proteins. It contains part if not all of the heredity info
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Define a Nucleosome
A basic unit of DNA packing
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What are the three types of RNA in the nucleus transcribed from DNA. Desribe their functions.
- rRNA, Used to make new ribosomes
- mRNA, codes for proteins
- tRNA, each represents an amino acid, used during translation to make polypeptide chains out of mRNA
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All of the RNA are synthesized where and are exported where
Synthesized in the nucleus and exported to the cytoplasm
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Heterochromatin is
Highly condensed transcriptionally inactive chromatin (looks dark in the cell)
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Where is chromatin often found in the cell
Attached to the nuclear lamina on the inner membrane of the nucleus
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Nuclear lamina
- Provides mechanical support for the nuclear membrane and controls the disassembly of the nuclear envelope in mitosis
- It is composed of intermediate filaments
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Euchromatin is
Much less condensed transcriptionally active chromatin (only mRNA and tRNA are transcribed from genes in these)
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Where are the new ribosomes made
The nucleolus, it also contains the genes that synthesize rRNA's
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What makes the nucleolus appear so dark
It contains so many nascent ribosomes in the process of assembly
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Ribosomes are composed of proteins that surround what
A core of rRNA
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The rRNA is transcribed where
Nucleolus
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What information do the Y chromosome contain
Only information necessary for men. Testosterone, sperm development ect.
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What is a kinetochore
This is what links chromosomes to microtubules at the centromere during mitosis
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What three DNA sequences are required to produce a eukaryotic chromosome that can be replicated
- Telomere
- Replication Origin
- Centromere
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Human peripheral lymphocyte
This is when two copies of chromosomes occupy distinct locations in a nucleus
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The NPC is
Nuclear Pore Complex, it is on the nucleus and is responsible for the movement of all macromolecules
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Signal for Nuclear Import
- Nuclear Localization Signal (NLS)
- Usually contains basic amino acids
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Signal for Nuclear Export
- Nuclear Export Signal (NES)
- Usually contains hydrophobic amino acids
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How is the unique amino acid sequence for protein delivery formed
After the protein is formed it folds with the signal on a tail, or at a crevice in the protein made of different segments of the protein folded to align them for recognition
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How does a protein end up in the right place after being made
It contains a unique amino acid sequence recognized by a carrier that binds it and takes it to its destination and releases it
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What happens to the protein carrier after delivering the protein
It recycles back to the cytoplasm
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What are the nuclear carriers that recognize NLS and NES
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Ran (ras-related nuclear protein) is
A small GTPase that regulates cargo binding and releasing for both importins and exportins
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Inhibition of splicing of the rRNA in the nucleolus would have what effect on its destination
If splicing doesn't happen exportation won't happen
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The exportation of rRNA is has a very tight relationship with
The splicing and processing of newly transcribed mRNA and its export
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Senescence is
The process of aging
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What are te primary differences in apoptosis and necrosis
- Necrosis is unplanned death, and the cell in a way implodes.
- Apoptosis is planned death and phagocytes consume the cell in efforts protecting cells surrounding it from its potentially harmful interior.
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In what conditions is apoptosis advantageous
- To delete unwanted features
- For the sculpting of tissues (webbing)
- To control the number of cells in the body
- For eliminating unwanted cells
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Why is apoptosis important for homeostasis
Homeostasis is a balance between cell proliferation and cell death
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Why would apoptosis be researched so heavily
If you can initiate planned death in infected cells you could cure a lot of diseases
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The severity of a noxious stimulant can effect cell death how
If it is too severe it will cause the cell to undergo necrosis, if severity is mild and the cell can't repair the damage done it will under go apoptosis
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What is the BCL2 family
A family of pro and anti apoptosis triggering proteins
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What is a caspase
This is the protein that apoptosis always ends with, they are cystein proteases and cleave proteins at the C terminal
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How many caspases does it take to initiate cell death
Just one molecule, every cell contains inactive ones
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What are the most important targets of caspases
- Nuclear lamina
- Cytoskeleton
- Destruction of these is what causes blebbing
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What is a key feature of apoptosis not seen in necrosis
The dying cell is engulfed by a phagocytic cell in apoptosis and no leakage of cellular contents therefore no inflammation response
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What are the physical manifestations of a cell undergoing necrosis
- The cell swells
- The cell bursts (Bleb)
- An inflammation response follows
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What are two other markers that will lead to cell death
Cytochrome C, and Phosphotidylserine being presented on the outside of a cell
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What are the two different activation pathways for apoptosis
Extrinsic and Intrinsic
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In general intrinsic apoptosis is initiated via the involvement of what organelle through what action
Mitochondria by the release of cytochrome C
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What signal on the outer leaflet of the cell membrane recruits phagocytes for apoptosis and how does it happen
Phosphatidylserine (normally only in the inner leaflet) it is flipped there by scramblase which is different then the one found active on the ER membrane
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Cytochrome C assembles with and activates caspase to form what
Apoptosome
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What do telomeres do and where are they located
Telomeres cap the ends of chromosomes so they can’t be degraded
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Knobs on chromosomes 13, 14, 15, 21, and 22 indicate
The positions of genes that code for rRNA
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All movement of macromolecules between the nucleus and cytoplasm occurs through
NPCs
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Completely folded proteins as well as large complexes can fit through the
NPC's (unlike protein import into the ER and mitochondria in which only unfolded proteins are small enough to cross the membrane).
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