Genetics and differentiation

Created by

Pierre Gasly

Cards (26)

What is determination
The process that leads up to the visible differentiated cell.
Describe the features of differentiated cells
They express a specific set of genes.
What regulates the formation of a differentiated state
Transcription factors activate a gene cascade
Briefly describe the gene cascade that leads up to differentiation
The master regulatory gene codes for specific transcription factors. These will eventually result in turning on cell specific genes.
Describe how a precursor cell is transformed to a differentiated cell
The master regulatory and cell specific genes are off in the precursor cell.
The master regulatory genes are on and the cell is determined.
When both the master regulatory and cell specific genes are on then the cell is differentiated.
What is a differentiated cell
This cell expresses visible cell changes
Describe the determination and differentiation of muscle cells
Embryonic precursor cells receive external signals.
The Master regulatory gene codes for a specific transcription factor [MyoD].
The cell is know determined and are known as myoblasts.
MyoD activates the gene cascade which produces muscle specific transcription factors.
The transcription factors activate the genes for muscle proteins and prevent cell division.
The myoblasts fuse to form muscle fibres.
What type of expression is used for MyoD [regulated or constitutive] why?
It is constitutively expressed. This is used as positive feedback and helps the cells to stay differentiated.
What did Christianne and Eric look at in drosophilia
They mutagenised flies to map the development of the offspring. This was used to discover the function of the genes.
What are the main phases in drosophilia development
Embryogenesis and organogenesis
Describe the development of drosophila
There is no cell division in the embryo for the first 4 hours.
Nuclear division forms the syncytial blastoderm, which has 4 main axes [These are Dorsal, Ventral, Posterior and Anterior].
The nuclei migrate and cell walls form the cellular blastoderm.
The segmented embryo forms.
And then the organs are formed.
How many segments are in the drosophila embryo
The head has 3.
The thorax has 3.
The abdomen has 9.
Which axis of the drosophila is the head
The anterior
Describe the bicoid mutant
When the offspring had a mutant bicoid gene the larva had no anterior end just two posterior ends. This showed that the bicoid gene develops the anterior axis.
What is an egg-polarity gene
These genes determine the polarity of the egg.
What type of gene is a bicoid gene
It is an egg polarity gene
Describe how the anterior and posterior axis develop in a drosophila
The nurse cell produce the bicoid mRNA that enters the egg while it is in the ovary.
The bicoid mRNA encodes for bicoid transcription factors that initiate a gene cascade.
In the early embryo there is a bicoid gradient from the anterior to the middle section of the embryo.
Why is Bicoid a maternal effect gene
This is because when the maternal gene is defective the egg fails to develop normally.
What is a morphogen
A gene that creates a gradient to determine polarity and position
Describe the genes present in drosophila development
Egg polarity genes develop the axis in the syncytial blastoderm.
The gap genes divide the embryo into broad areas.
The pair rule genes establish pairs of segments.
The segment polarity genes establish the anterior and posterior axes of each segment.
The Homeotic genes develop the organs.
What are the types of segmentation genes in drosophila
Gap, pair rule and segment polarity.
What is the Kruppel mutant in drosophila
These are produced by a mutation in the gap gene. They are missing some segments.
Describe the ultrabithorax mutant
This is caused by a homeotic mutation.
This type of mutation affects the placement of the organs.
The 3rd thoracic segment is replaced by a copy of the 2nd thoracic segment.
This means that they have an extra pair of wings and legs instead of a haltere.
What do homeotic mutations do
They are dominant mutations that change the identity of body parts.
What do hometoic genes do
They determine the identity of embryonic regions.
They code for transcription factors.
They occur in clusters which are arranged in the same order as the regions that they affect.
What is colinearity
When genes are ordered in the same order as the regions that they affect.