module 6 - 19.3 & 19.4 genetic control of body plans Flashcards
what is a body plan?
observable, spatial arrangement of an organisms body parts
what are homeobox genes?
- a gene that controls the initial development of an organisms body plan
- highly conserved by natural selection
what is the DNA like in homeobox genes?
double helix
what do homeobox genes code for?
- code for transcription factors which control the expression of structural genes
- when these genes are expressed they ensure body plan is developed correctly
what type of gene is a homeobox gene?
a regulatory gene
what is a homeodomain?
the binding site of a transcription factor (produced by homeobox)
what codes form a homeodomain?
- a specific DNA sequence within the homeobox gene
- binding site for transcription factors DNA
what do all human homeobox genes contain?
the exact same homeobox, exact same sequence of 180 base pairs
what happens if mutations occur in an organisms homeobox genes?
- its unlikely to survive
- so mutations in homeobox genes are selected against by natural selection
what do structural genes do in DNA?
ensure development of a body plan
why are homeboxes and homeobox genes highly conserved by natural selection?
because the homeobox found in animals, plants and fungi are remarkably similar
what are hox genes?
- type of homeobox gene only found in animals
- gene that is involved in the symmetry of an animal
what is a homeobox?
DNA sequence inside a homeobox gene
what does a homeobox (not homeobox genes) code for?
transcription factors homeodomain
when do body plans develop?
in an organisms embryonic stage
which processes control the development of an organisms body plan?
- mitosis
- apoptosis
how does mitosis control the development of an organisms body plan?
during cell cycle, mitosis causes cells to divide which produces new cells for growth, repair and reproduction
how does apoptosis control the development of an organisms body plan?
causes cells to die which removes old cells or cells that are no longer needed
what are mitosis and apoptosis controlled by?
- hox genes, which respond to internal and external stimuli
- depending on stimulus hox genes either initiate mitosis or apoptosis
what are master control genes?
genes that control development
what are the 2 types of DNA affected by transcriptional factors?
- promoters (stimulate transcription)
- enhancers (increase/decrease likelihood of transcription)
what is a typical mechanism used by transcriptional factors to regulate gene expression?
stabalise or blo1ck binding of RNA polymerase to DNA
