Test 1 Flashcards
(141 cards)
1
Q
Stages of development
A
- Fertilization
- Cleavage
- Gastrulaton
- Organogenesis
- Larval stages
- Maturity
- Gametogenesis
2
Q
Morula
A
Solid ball of cells
3
Q
Blastula
A
Hollow ball of cells
4
Q
Blastomere
A
1 cell within the blastula
5
Q
Fertilization
A
Union of male and female gametes to form the diploid zygote
6
Q
Cleavage
A
Synchronized mitotic cell divisions of a fertilized egg that results in formation of blastomeres and changes the single celled zygote into a multicellular embryo
7
Q
What happens to the embryo size during cleavage
A
Embryo size stays the same, cell size gets smaller and smaller
8
Q
Gastrulation
A
Big cell movements. Transformation of the blastula to the gastrula and development of germ layers
9
Q
Axis development
A
Developing a left/right, anterior/posterior, dorsal ventral, and proximal distal axis
10
Q
What governs the different types of cleavage
A
The amount of yolk determines the cleavage patterns
11
Q
Where does division occur if there is a lot of yolk
A
Division only at the top
12
Q
Invagination
A
Infolding of a sheet (epithelium) of cells, much like the indention of a soft rubber ball when its poked
13
Q
Involution
A
Inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells
14
Q
Ingression
A
Migration of individual cells from the surface into the embryos interior (move away from neighbors, loss of cadhesion)
15
Q
Delamination
A
Splitting one cellular sheet into two or more parallel sheets
16
Q
Epiboly
A
Movement of the epithelial sheets spreading as a unit to enclose deeper layers of the embryo
17
Q
Germ layers
A
Ectoderm, mesoderm, endoderm
18
Q
Ectoderm
A
Skin and CNS
19
Q
Mesoderm
A
Bones and muscle
20
Q
Endoderm
A
Organs (respiratory and digestive tract)
21
Q
Methods of tracking cells
A
- Fate maps
- Direct observations of living embryos
- Dye markings
- Genetic labeling
- Transgenic DNA chimeras
22
Q
Epithelial cells
A
Have tight connections to neighboring cells (do not move–> only move in epiboly but do not leave neighbors)
23
Q
Mesenchymal cells
A
Are loose or unconnected to one another and can move
24
Q
Fate maps and methods
A
Following a cell through development using dyes to see what each cell would turn into
- Dye marking
- Flourescent dye
- Chimera
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Dye marking
Method of creating a fate map. Most cells are colorless, dyes stain cells but dont kill them
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Chimera
Tissue from the embryo of one animal is removed and replaced by another using a graft (tissue a different color or labelled)
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Transgenic DNA chimeras
Donor embryo is infected with a virus with a gene to express GFP. Infected cells glow green in UV light. Glowing cells transplanted into a host embryo and track movement
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Why is evolutionary embryology important
Embryos pass through the same developmental stages as their ancestors
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Homologous
Similaity based on a common ancestor
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Analgous
Perform similar function but do not have a common ancestor
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Causes of abnormalities
Generic mutation
Environmental cause
Multifctorial
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Types of genetic mutations
1. Gene mutations
2. Chromosomal aneupolidy
3. Translocations
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Environmental causes of mutations
1. Teratogen - chemicals, viruses, radiation, hyperthermia
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Multifactoral causes
Combination, we are not sure
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Differentiation
Development of cellular specialization
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What step comes before differentitation
Commitment
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Parts of comitment
1. Specification
| 2. Determination
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Specification
Capable of differentiating autonomously when placed in a neutral environment, not in non neutral environment (reversible)
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Determination
Capable of differentiatin autonomously even when placed into another embryonic region (irreversible)
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Where do the factors come from that create specification
1. Cell has components within it that causes it to become that cell type
2. Neighboring cells influence cells to be specified
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Autonomous specification
Removed blastomere will produce the same cells it would if it were still part of the embryo. The embryo will lack the cells taken
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Morphogenic determinants
Molecules of transcription factors that will influence gene expression that directs a cell into a particular path of development. The cell knows very early what it will become
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Where does the cell get morphogenic determinants
From mother
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Conditional specifiation
Each cell origially has ability to make many different cell types. Interactions with other cells restricts the fate of one or both participants. Fate of cell depends upon the conditions in which the cell finds itself
- Cells retain identity but grow according to the cells around them (flag)
45
What are cell comittment and differentiation programmed by
morphogen gradients
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Differential gene expression
Process by which cells become different from one another based upon the unique combination of genes that are active or expressed
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What does expression of different genes cause the production of
Proteins that lead to the differentiation of different cell types
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Three postulates of differential gene expression
1. Every somatic cell nucleus of an organism contains the complete genome established in the fertilized egg (DNA of all differentiated cells is identical)
2. Unused genes in differentiated cells are neither destroyed nor mutated. They retain potential for being expressed
3. Only a small percentage of the genome is expressed in each cell and a portion of the RNA synthesized in each cell is specific for that cell type
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Regulaiton of gene expression
1. Differential gene expression: regulates which nuclear genes are transcipred into nuclear RNA
2. Selective nuclear RNA processing: regulates which of the transcribed RNAs are able to enter the cytoplasm and become mRNA
3. Selective messanger RNA translation: regulated which of the mRNAs in the cytoplasm are changed into proteins
4. Differential protein modification: regulates which proteins are allowed to remain or function in the cell
50
The genome across all cells is the same but ______ is not
the expression of the same mRNA across all cells
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Explanation behind cloning
If each cells nucelus is identical to the zygote nucleus then each cells nucelus should be capable of developing an entire organism
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Chromatin
DNA and protein complex found in eukaryotic genes (DNA and histones condensed --> no access to genes)
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DNA histone complex
Called nucleosome
| DNA wound around histones
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Histones
Protein component made up of an octamer of histone proteins
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Nucleosome
The histone plus about 147 bp of DNA that wraps around it in two loops with many contact points
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Heterochromin
Tightly packed DNA around histones
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Euchromatin
Loosely packed DNA around histones
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What is gene expression dependent upon
How tightly packed a given region of chromatin may be (regulating if genes are accesible for transcription)
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What two groups modify the H3 and H4 tails
- Methyl (CH3)
| - Acetyl (COCH3)
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Histone acetylation
Loosens histones and promotes transcription
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What causes histone acetylation
Histone Acetyltransferases
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Histone methylation
Tightens histones and promotes transcriptional repression
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What causes histone methylation
Histone methyltransferases
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What could methylation also do to the histone
It can activate transcription depending on the amino acid being methylated and the presence of acetyl or methyl groups in the vicinity
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Exons
Regions of the DNA that code for parts of the protein
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Introns
Regions of the DNA that have nothing to do with the protein sequence
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Parts of a gene `
1. Exon
2. Intron
3. Promotor
4. Transcription initiation site
5. 5' untranslated region
6. Translation initiation site
7. Translation termination codon
8. 3' untranslated region (3' UTR)
9. Transcription termination sequnece
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Promotor region
Where RNA polymerase II binds to intiate transcription. Same have the sequence TATA (tata box) which binds to TBP and helps anchor RNA polymerase II to the promotor . Where proteins are prepared for transcription to occur
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Where is the promotor region located
In front of the gene
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Transcription initiation site
The DNA sequence that will code for the addition of the 5' cap after the RNA is transcribed
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What does the cap sequence begin
It begins the first exon
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5' untranslated region
Determines the rate at which translation is initiated
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Translation initiation site
ATG (AUG in RNA). This codon is found after the translation initiation site (distance varies). ATG translation start sequence is the same in every gene
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Translation termination codon
TAA (UAA in mRNA). When ribosome enters this codon, the ribosome dissociates and protein is released. Can be TAG or TGA in other genes
75
3' untranslated region
Transcribed but not translated into protein. Has the sequence for polyadenylation (addition of tail)
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Roles of polyA tail `
1. confers stability on mRNA
2. Allows mRNA to exit nucleus
3. Permits the mRNA to be translated into protein
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Transcription termination sequence
Transcription continues beyond the AATAAA site for about 1000 nucleotides before being terminated (end portion of mRNA)
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Cis regulatory elements
The on, off and dimmer switches of a gene
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Cis
Located on the same chromosome
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Cis regulatory elements of DNA
Promotors
Enhancers - like promotors
Silencers - prevent transcription
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Cis regulatory elements of proteins
Transcription factors
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Promotor
Sites where RNA polymerase binds to initiate transcription. Promotors usually have a 1000 bp site of repeating CG
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CpG islands
Repeating CG
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Enhancers
Control the rate and efficiency of transcription from a specific promotor, recruit and stabilize RNA polymerase
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Silencers
Prevent promotor use and inhibit gene transcription
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Basal transcription factors
Bind to CpG islands. They also recruit RNA polymerase and orient it
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What will other transcription factors do
Bind to enhancers activating genes
88
What is the job of transcription factors
1. Recruit enzymes to break up the nucleosomes in the area (histone acetyl transferases to make it accesible for RNA polymerase)
2. Loop the chromatin so that the enhancer with all its tanscription factors will be brought closer to the promotor (creates a bridge)
89
Differential RNA processing
Splicing of the mRNA precursors into messages that specify different proteins by using different combinations of potential exons
90
Splicing isoforms
Different proteins encoded by the same gene
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Alternative nRNA splicing
Producing a wide variety of proteins from the same gene, and most vertebrate make nRNAs that are alternatively spliced
92
How does the cell know where an exon ends and intron begins
Consensus sequences
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Consensus sequences
found at the 5' and 3' end of an intron. These sequences are splice sites of an intron
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What splices nRNA at consensus sequences
Spliceosomes
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Spliceosomes
Small nRNA that bind to splice sites
96
Splicing factors
Made up of proteins that bind to the splice sites or to areas adjacent to them
97
How does alternative splicing occur
Specific splicing factors are produced. Each cell type produces a different set so an exon can be included in one and omitted in another
98
Control of gene expression at the level of translation
1. Differential mRNA longevity
2. Stored oocyte mRNAs selective inhibition of mRNA translation
3. Ribosomal activation of mRNA translation
4. microRNAs: specific regulation of mRNAs translation and transcription
99
Differential mRNA longevity
- not all mRNA lasts for the same amount of time after transcription
- mRNA is easily destroyed in the cell
- the longer mRNA lasts, the more protein can be translated from it
100
Stored oocyte mRNAs selective inhibition of mRNA transation
Oocyte makes and stores mRNA prior to meiosis to be used after fertilization
101
What are stored mRNAs called
Maternal contributions
102
Why are maternal contributions benefitial
The zygote does not need to have any trascription or traslation and can go right into cleavage after fertilization using up the mRNA and proteins deposited by its mother
103
What will not occur is maternal contributions are used up
Gastrulation
104
What keeps maternal contributions in a dormant state
There has to be an inhibitor. Maskin (protein) forms repressive loop structures by bringing 5' and 3' ends together in oocytes
105
What removes the inhibition sequence
Progesterone
106
What stimulates progesterone release and what does it lead to
Ovulation Stimulates progesterone release which triggers translation of the mRNA
107
Morphogenesis
Construction of different shapes and organs. Cells must be differentiated
108
What causes changes
Protein-protein interactions
109
What mediated cell communication and where do they come from
Informational molecules secreted or positioned in the cells membrane
110
Juxtacrine signaling
Contact dependent. A cell is communicating to a neighboring cell (must touch)
111
Paracrine signaling
Neighboring cells. A cell is communicating to cells surrounding it and further away
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Ligand
A protein secerted from a cell designed to communicate with another cell
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Receptor
Proteins within a membrane designed to bind to signaling proteins or a ligand
114
Homophilic binding
A receptor in the membrane of one cell that binds to the same type of receptor in another cell
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Heterophilic binding
Occurs between two different receptor types
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What does binding of a receptor to a ligand do
1. Changes the extracellular receptor shape (dimerize)
2. Changes the intracellular receptor shape (phosphorylate)
3. Causes a cascade of events within the cell
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Differential cell affinity
Experient: embryos mixed but went back to normal
| - cells must have already recieved signal to know where theyre supposed to be
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Term for cells knowing where to go back to when mixed
Selective affinity
119
How do cells sort themselves
- Cells with greater cohesion migrate centrally compared to those with less surface tension (more contact possible = move inward)
120
"Glue" on the cell surface that connects them to other cells
Cadherin
121
Cadherins
Calcium dependent adhesion molecules. Transmembrane proteins that interact with cadherins on other cells
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What anchors the cadherins inside the cell
Catenins
123
Where is cadherin located
Transmembrane
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How does one cell leave another cell
Change its plasma membrane to no longer have cadherin on it. Will detach from other cell
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Quantity and cohesion
The more cadhesion, the more surface tension
| Linear relationship
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What can cadhesion expression affect
The timing of developmental events
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Signal transduction cascades
- Fibroblast growth factors and RTK
- Hedgehog
- Wnt
- TGF-B superfamily
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Basic blueprint of a signal transduction
1. A signal
2. A receptor for that signal
3. Mechanism to translate or transport the signal
4. Mechanism to translate the signal to a stimulation or repression of gene expression
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What is it called when receptors come together after ligand binding
Dimerized
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What causes the cascade inside the cell in RTK
phosphorylation
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What type of molecules phosphorylates
Kinase
132
End goal of RTK
Stimulation or repression of gene expression
133
What activates a protein
Phosphorylation
134
RTK pathway
1. Ligand
2. RTK
3. GEF
4. RAS
5. RAF
6. MEK
7. ERK
8. Transcription factor
9. Transcription
135
What dephosphorylates RAS to stop transcription
GAP
136
What happens if RAS is stuck turned on
Uncontrolled growth (cancer)
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No Wnt pathway
Beta catenin is destroyed
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Wnt bound pathway
B catenin binds in the nucelus and turns on gene transcription
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TGF-B superfamily pathway
1. TGF-B ligand
2. Receptor II
3. Receptor I
4. Smad activation
5. Smad dimerization
6. New transcription
140
Acetylation of tails along with addition of 3 methyl groups causes
Actively transcribed chromatin
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Lack of acetylation with methylation of lysine in 9th position of H3 is associated with
Highly repressed chromatin
