1- Devolpmental Biochemistry Flashcards
1- what are cell developmental signals ?
The cell development signals are the basic mechanisms of cell fate determination.
2- how are the all the steps in development are programed by developmental signals ?
All the steps in development are programmed and have a reproducible pattern controlled by the developmental signals.
How does developmental signaling take place ?
1- Direct intercellular interactions
2- Diffusible substances ( Morphogens ) released by other cells .
What are the 6 major morphogens ?
1- bicoid
2- sonic hedgehog (SHH)
3- wingless (WNT)
4- retinoic acid (RA)
5- Bone morphogenetic protein (BMP)
6- Fibroblast growth factor
What is the ventricular zone ?
The ventricular zone is cross-section through the nervous system early in development
What is the function of glial cells?
Glial cells help to guide the migration of newly formed neurons
? what is retinoic acid
Tonic acid is a morphine and a derivative of vitamin A ( retinol )
? what is retinoic acid
Tonic acid is a morphine and a derivative of vitamin A ( retinol )
What are morphogens ?
Morphogens are signaling molecules involved in the patterning of cells during embryogenesis
How does the morphogens determine tissue pattern during morphogenesis ?
The Morphogens use their non-uniform distribution to determine tissue pattern during morphogenesis
How happens when retinoic acid patterns vertebrate embryos ?
Retinoic acid patterns, vertebrate embryos by forming an interior to posterior (A – P) concentration gradient.
How happens when retinoic acid patterns vertebrate embryos ?
Retinoic acid patterns, vertebrate embryos by forming an interior to posterior (A – P) concentration gradient.
How does retinoic acid switch retinoic acid receptors from repressor to transcriptional activators?
Retic acid act as a ligand for transcription factors of the retinoic acid receptors (RAR) nuclear receptors superfamily, switching them from receptors to transcriptional activators
How does a high dose of retinoic acid interfere with the normal developmental process?
Retic acid alters the expression of Hox genes in early gestation ( first month post-fertilization in humans)
How does a high dose of retinoic acid interfere with the normal developmental process?
Retic acid alters the expression of Hox genes in early gestation ( first month post-fertilization in humans)
What happened when a mouse embryo is exposed to retinoic acid ?
When retic acid is given to a mouse embryo during morphogenesis result in severe skeletal deformities.
What happens when a pregnant woman uses retinoic acid for treatment of acne?
Pregnant woman using retinoic acid for treatment of acne has bear defects.
What is the similarity between insecticide metamorphic and retinoic acid?
-The molecular structure of degradation product of insecticide metamorphic is similar to retinoic acid.
-Methoprenoic acidn (MA) can buy two retinoic acid receptors on cells and activate them,
What happens when environmental pollution with industrial discharge of chemicals ?
Birth defects and abortion
What are the early embryonic genes and what is there use?
Early embryonic genes (maternal effect, genes and segmentation genes) express proteins that set up the orientation and define the body segments.
What is the function of the homeotoic genes?
The homeotic genes act on the segments to make the body parts distinct to each segment and regulate differentiation.
What is the function of the homeotoic genes?
The homeotic genes act on the segments to make the body parts distinct to each segment and regulate differentiation.
What are the genes encoded proteins called and what is its function ?
The jeans and coded protein is called transcription factors that direct cells to form various parts of the body.
What is the use of Drosophila?
Most of what we know about molecular basis of animal development has come from the studies of model systems, such as Drosophila.
What is the similarity between drosophila and human development?
Drosophila and human development, utilize closely regulated, genes working in highly conserved regulatory cascades
What is the difference between Drosophila and human development?
Drosophila is subject to easy genetic manipulation as experiments with poor animals is not unethical
What is the difference between Drosophila and human development?
Drosophila is subject to easy genetic manipulation as experiments with poor animals is not unethical
Why the Drosophila melanogaster has been chosen as a developmental model ?
1– fruit fly (easily obtained)
2- short developing period (7 days)
3- sure life cycle (30 days)
4- well defined genome
What is segmentation?
Segmentation defines body segments. It is a simple and universal solution for increased function.
What are the three major classes of genes that control segmentation and differentiation?
A. Maternal effect genes.
B. Segmentation genes ( gap genes . Pair-rule genes , segment polarity genes
What are the three major classes of genes that control segmentation and differentiation?
A. Maternal effect genes.
B. Segmentation genes ( gap genes . Pair-rule genes , segment polarity genes )
C. Homeotic selector (HOX) genes
What does body segment and HOX genes do?
Body segments differentiate.
HOX genes tell which segment should have legs, wings, etc.
What does body segment and HOX genes do?
Body segments differentiate.
HOX genes tell which segment should have legs, wings, etc.
What are maternal effect genes responsible for?
Maternal effect genes are responsible from head to tail polarization, mutations in these genes will destroy cellular polarization and result in monster mutants that cannot survive.
What is an dicephalic or bicaudal embryo ?
-Dicephalic is a two headed embryos with no tail
-Bicaudal is a two tailed embryo with no head
Why is the polarization of the zygote good essential?
The polarization of the zygote is essential for the development of the embryo correctly.
What is polarity?
Polarity is the head to tail and top to bottom orientation of the embryo.
What are the material that are distributed and equally in the cell or zygote ?
The cytoplasmic Determinations are distributed equally in egg or zygote. Like mRNA, proteins, yolk, etc.
As the cell divides what happens when these materials are distributed and equally to daughter cells?
As the cell divides these materials are distributed and equally to the cell resulting in polarity of the cell/embryo.
How is the Drosophila oocyte is head to tail polarized by nurse cells?
The polarization is succeeded, mostly by the mRNA of the bicoid proteins secreted by nurse cell from the atrium
What happens when theBicoid protein concentration gradually decreases from head to tail?
When theBicoid protein concentration gradually decreases from head to tail a bicoid protein gradient is formed.
In the segmentation genes, what does gap genes do?
Gap genes Divide the embryo into several broad regions, their mutations lead the gaps in the segmentation patterns.
What happens in the pair-rule genes In the segmentation genes?
The pair-rule genes divide gaps into segments mutations lead to loss of portions of every second segment,
What happens in the segment polarity genes in the segmentation genes?
The segment polarity, genes specify the polarity of development segments embryo with engrailed mutation slug, the posterior compartments of each segment.
What is the function of homeotic selector genes?
Homeotic selector genes are “ master” in the control network governing segmental differentiation it’s products serves segmental differentiation to different body parts
What is the use of homeotic selector genes?
It it gives the functional characteristics of the segments of an organism
What does mutations in the homeotic genes provide?
It provides some of the most competing evidence for their importance in the development of the segment of the organisms
what is the function of the HOX genes ?
HOX genes code for controller proteins that turn genes on and off.
What happens when activating HOX genes protein in a cell ?
It will change the activities of dozens/hundreds of genes does changing the properties of the cell and tissue it’s in
What is Homeobox?
It is homeotic genes containing a sequence of 180 nucleotides
What does homeobox contain?
It contains about 30% basic amino acid (Arg and Lys)
What is homeodomain ?
Homeodomain it is the homeobox codes for a 60 amino acid homeotic polypeptide.
What does the homeodomain folded into?
It folds into a 60 amino acid helix – turn – helix (HTH) structure in which three alpha helices are connected by short loop regions.
What does the homeodomain helix– turn – helix bind to?
It is able to bind to DNA
What are the types of homeotic genes of D. Melanogaster ?
1- antennapedia complex ( ANT-C ) which affects the development of head and thoracic segments.
2- bithorax complex (BX-C) which controls development of the Thor and abdominal segments.
What is an example for the antennapedia mutation?
Legs grow from the head of a fly instead of the expected antigen
What is an example of bithorax mutation ?
When drosophila Has four wings instead of two
What is the name of the for chromosomal clusters of the human homeobox genes ?
HOXA, HOXB, HOXC, HOXD
In humans, what is the result of the mutations in the HOXD13 result in ?
It results in syndactyly which is a malformation characterized by fusion of digits
What happens when a gene is not needed for a cell type?
It is turned off by adding a methyl group (methylation)
How is DNA methylated ?
It is methylated by DNA methyltransfers (DNAMT)
How does DNA methylation repress a gene transcription?
When located in a gene promoter
What are the two out of four bases that can be methylated?
Cytosine and adenine
Why is DNA mutilation essential for normal growth?
1-Silencing retroviral elements
2-Regulating tissue – specific gene expression
3-Genomic imprinting
4-X chromosome inactivation
What happens in the inhibition of DNA with inhibition in mice?
It results in death before birth
What happens in the X-chromosome inactivation?
X – inactivation prevents them from having twice as many X chromosome gene product as male who all process a single copy of the X chromosome
What is apoptosis?
the death of cells which occurs as a normal and controlled part of an organism’s growth or development.
What happens in a ptosis during metamorphosis of a third pole into a frog?
The cells in the tadpole tail are induced to undergo apoptosis so The tail is lost thus an increase in the thyroid hormone and blood simulate all the changes.
How is apoptosis used in human?
Formation of a mature hand is achieved through a apoptosis.
The webbing of human digits .
