The programming of
development
Complex multicellular organisms develop from a single undifferentiated cell = zygote
Zygote divides and differentiates as they form specialised cells
Development process is under strict genetic control- each differentiated cell type expresses
a cell-type specific subset of genes in their genome
To understand how and organism develops we must use genetic identification an analysis
techniques
We often use model animals to try and understand development as humans are too
complicated
Animals used
Caenorhabditis elegans (C. elegans)- this is a nematode worm. Compromises of only 1021
cells. Large amounts can be grown quickly. Can be seen through microscope. Short life cycle
(3.5 days) so rapid experiments can be carried out. 2 sexes, males and hermaphrodites
which allows for self and cross fertilization
Drosophila melanogaster-fruit fly. Short life cycle and large numbers are easily propagated.
Genome completely sequenced
Danio rerio- zebra fish (model vertebrate). Short life cycle and large numbers of progeny.
Eggs are transparent so can be seen under microscope. Small genome that is largely
sequenced.
Mus musculus- this is a mouse. 60 years of genetic analysis. Best genetically studied
mammal. Short life cycle, many offspring. Very advanced sequenced genome. Very good for
looking at human development
Arabidopsis thaliana-wall cress. Small genome. Completely sequenced. Preferentially self-
fertilise but can be crossed. Produce thousands of seeds. Many years of genetic analysis.
Good model for looking at plants.
Why is this important?
We can learn a lot about the way in which genes regulate complex processes like
development by isolating mutants in which the process has been perpetuated
It is important to know that there are SEPARATE genes that regulate development and that
are regulated by development
We can identify genes that regulate development using genetics
If a mutation in a single gene changes the developmental process then this will enable us to
identify the gene that is mutated and well know how the switch in cell fate is determined
Simple model of developmental process:
Bacteriophage T4 assembly- simple lifecycle, phage infects E.coli and uses bacterial genetic
machinery to display bacteria phage programming
first of all there is temporal programming of development. Some genes need to be
expressed early in infection so that other genes expressed by phage genome can be
expressed.
Its regulated through the promoters of the later expressed bacteriophage genes
the late genes usually encode the viral coat proteins
in bacteriophage T4 there Is a mutation in genes 33 and 55 these block the expression of the
late genes therefore mediate the early and the late switch
development
Complex multicellular organisms develop from a single undifferentiated cell = zygote
Zygote divides and differentiates as they form specialised cells
Development process is under strict genetic control- each differentiated cell type expresses
a cell-type specific subset of genes in their genome
To understand how and organism develops we must use genetic identification an analysis
techniques
We often use model animals to try and understand development as humans are too
complicated
Animals used
Caenorhabditis elegans (C. elegans)- this is a nematode worm. Compromises of only 1021
cells. Large amounts can be grown quickly. Can be seen through microscope. Short life cycle
(3.5 days) so rapid experiments can be carried out. 2 sexes, males and hermaphrodites
which allows for self and cross fertilization
Drosophila melanogaster-fruit fly. Short life cycle and large numbers are easily propagated.
Genome completely sequenced
Danio rerio- zebra fish (model vertebrate). Short life cycle and large numbers of progeny.
Eggs are transparent so can be seen under microscope. Small genome that is largely
sequenced.
Mus musculus- this is a mouse. 60 years of genetic analysis. Best genetically studied
mammal. Short life cycle, many offspring. Very advanced sequenced genome. Very good for
looking at human development
Arabidopsis thaliana-wall cress. Small genome. Completely sequenced. Preferentially self-
fertilise but can be crossed. Produce thousands of seeds. Many years of genetic analysis.
Good model for looking at plants.
Why is this important?
We can learn a lot about the way in which genes regulate complex processes like
development by isolating mutants in which the process has been perpetuated
It is important to know that there are SEPARATE genes that regulate development and that
are regulated by development
We can identify genes that regulate development using genetics
If a mutation in a single gene changes the developmental process then this will enable us to
identify the gene that is mutated and well know how the switch in cell fate is determined
Simple model of developmental process:
Bacteriophage T4 assembly- simple lifecycle, phage infects E.coli and uses bacterial genetic
machinery to display bacteria phage programming
first of all there is temporal programming of development. Some genes need to be
expressed early in infection so that other genes expressed by phage genome can be
expressed.
Its regulated through the promoters of the later expressed bacteriophage genes
the late genes usually encode the viral coat proteins
in bacteriophage T4 there Is a mutation in genes 33 and 55 these block the expression of the
late genes therefore mediate the early and the late switch
