19.3 Body Plans Flashcards
In order for cells in developing organisms to differentiate and specialise what must they do
They must be able to control which genes are functioning at a particular time
This is achieved by switching on and switching Off genes
Must occur in specific tightly controlled sequence which is determined by transcription factors
What is morphogenesis
The regulation of the pattern of anatomical development
What are Homeobox genes
They are a group of genes which all contain a homeobox
What is a homebox
Is a section of DNA 180 base pairs longs that is highly conserved in plants animals and fungi
What does homeodomain do
This part of the proteins binds to DNA and switches other genes on or off making homeobox genes regulatory genes
Homeobox genes in humans and mice have
Identical nucleotide sequences
What is pax 6
Is a Homeobox gene
When mutated causes a form of blindness
This has also been observed in mice and fruit flies
What are hox genes
A group of Homeobox genes that are only present in animals
They are Responsible for correct positioning of body parts
What is the arrangement of hox genes in animals
They are found in genes clusters
- mammals have four clusters on different chromosomes
Order in whcih genes appear along chromosomes is the order in which their effects are expressed in the organisms
How are body plans represented
They are represented as cross sections through the organisms showing the fundamental arrangement of tissue layers
The individual vertebrae and associated structures have all developed from what
From segments in the embryo called somites
Somites are directed by hox genes to develop in a particular way depending on position in the sequence
The body shape of most animals shows symmetry what are they
Radical symmetry
Bilateral symmetry
Asymmetry
What is apoptosis
Shapes different body parts
By removing unwanted cells and tissues
Cells undergoing apoptosis can release chemical signals which stimulate mitosis and cell proliferation leading to the remodelling of tissues
What factors affect the expressions of regulatory genes
Can be influenced by the expression both internal and external
These factors wills be a greater impact during the growth and development of an organism
