Module 36 Flashcards
Cell Specialization and Development
Where do all cell types derive from
the zygote
What allows gene specialization
gene regulation
all cells have the same or very similar genes, but the genes are not expressed and some repressed
Development
the process in which fertilized eggs undergoes multiple rounds of cell division to become an embryo with specialized tissues and organs
Differentation
When cells become progressively more specialized
caused by gene regulation
Totipotent Cells
A cell that can give rise to a new, complete living organism
ex. a fertilized egg
Pluripotent Cells
They can become or give rise to any cell but can’t make a whole new organism on their own
Multipotent Cells
This can give rise to a limited type of cells
What do pluripotent, totipotent, and multipotent cells all have in common
they are all ste cells
Stem cells
Capable of becoming into different cells
Why do cells increasingly lose their developmental potential?
As they become committed to a certain pathway, genes that are not needed get turned off, or repressed, and become difficult to turn on again.
2 hypothesis on why differentiation cells lose their developmental potential?
Gene regulation and genome reduction
What prove gene regulation is the reason as to why cells lose their developmental potental
Differentiated cells could be REPROGRAMMED to become stem cells again
- because genes would still present
Cells that are further along in development are harder to reprogram
What happens when nucleic transfers succeed
A clone, share the same genome
What is a clone
An individual that carries an exact copy of the genome of another individual
Regenerative Medicine
Aims to use the natural process of cell growth and development to replace diseased or damaged tissues
How can adult differentiated cells be reprogrammed to become stem cells
-demonstrated by Japanese scientists
By the activation of a handful of genes, most of which encode for TRANSCRIPTION FACTORS or chromatin proteins
-These key genes will turn on other gene, returning cells to earlier states
Genome
All the DNA present in a living organism
Complete set of genetic info
Evolutionarily conserved
It is shared by a common ancestor and is conserved for a long period of time across many species, which will evolve to continue having these traits or features
Spherical Lens
improves eye focus, improving images, allowing organisms to detect prey and avoid predators
The Retina
Where light is focused on
Light-sensitive tissue
Compound Eyes
Consists of hundreds of small lenses arranged on a convex surface, pointing in many slightly different directions, allowing a wide view and detecting rapid movement.
Cambrian Explosion
The extraordinary differentiation of animals
542 million years ago
Hypothesis of eye diversity
They evolved independently in different organisms
They evolved once and diverged over time`
What supports the hypothesis that eyes only evolved once.
Light-sensitive molecules in all light-detecting cells are the same: Opsin
Tells that it was retained over time from a common ancestor
Opsin
A light-sensitive molecule associated with vitamin A found in all light-detecting cells
The Eyeless Gene
In fruit flys
Produced a transcription factor pax6
Pax 6
Transcription factor
Turns some genes on and others off
Turns on pathways for eye development, but produces a variety of different eyes
Aniridia
Absence of iris
Transcription factors can act as both activators or repressors of a gene
True
Why is pax6 considered a master regulator
the activation of one gene (by this transcription factor) can turn on an entire developmental pathway
Why can master regulators produce a variety of one trait
The downstream genes that are targeted by the transcription factor are different in different organisms
Weather a gene is turned on or off is dependant on what
The combination of transcription factors that are present in the cell and bound to DNA
AND
The balance of transcription factors that are activators and the ones that are repressors
(combinatorial control)
Combinatorial control
The regulation of gene transcription according to the mix/combination of transcription factors in the cell
Meristem cells
They are like the stem cells of plants
Consist of cells that can differentiate into different structures
Whorl
Flowers develop from these patterns of FOUR CONCENTrIC CIRCLES OF CELLS into distinct types of floral structures
How are floral organs formed
From the outermost (whorl 1) to the innermost whorl (whorl 4)
