section 1: cellular control - topic 2: body plans Flashcards
what is a body plan?
the general structure of an organism?
how do proteins control the development of a body plan?
they help set up the basic body plan so that everything is in the right place.
what are hox genes?
the genes that code for the proteins that control body plan development.
what are homeobox sequences?
regions of hox genes that are highly conserved.
^ means that these sequences have changed very little during the evolution of different organisms that possess these homeobox sequences.
what does the homeodomain do?
it binds to specific sites on DNA, enabling the protein to work as a transcription factor.
what do homeboy sequences code for?
a part of the protein called the homeodomain.
where do the proteins bind to DNA?
at the start of developmental genes, activating or repressing transcription - so altering the production of proteins involved in the development of the body plan.
what 2 ‘sis’ words are involved in the development of body plans?
mitosis.
apoptosis.
what is apoptosis?
programmed cell death.
what are the main steps in apoptosis?
enzymes inside the cell break down cell components.
the cell shrinks and begins to fragment.
phagocytes engulf and digest the cell fragments.
what is the role of apoptosis in development?
apoptosis refines the body parts by removing unwanted structures.
what is the role of mitosis in development?
mitosis and differentiation create the bulk of the body parts.
examples of apoptosis?
when hands and feet first develop, fingers and toes are connected - they’re only separated when cells in the connecting tissue undergo apoptosis.
as tadpoles develop into frogs, their tails are removed by apoptosis.
an excess of nerve cells are produced during the development of the nervous system - nerve cells that aren’t needed undergo apoptosis.
what can the genes that regulate mitosis and apoptosis respond to?
internal and external stimuli.
example of an internal stimulus.
DNA damage.
if DNA damage is detected during the cell cycle, this can result in the expression of genes which cause the cell cycle to be paused and can even trigger apoptosis.
