Homeobox genes Flashcards
(12 cards)
Define morphogenesis:
Regulation of the pattern of anatomical development.
Genetics of fruit flies
What are homeobox genes?
Regulatory gene
Homeobox = section of DNA (180 base pairs long)
~> Codes for part of protein (60AA) called homeodomain
Highly conserved
Homeodomain binds to DNA = switches genes on or off
How do homeobox genes control development?
Act as transcription factor
Can bind to DNA at start of developmental genes –> activating/repressing transcription
This alters production of proteins involved in development of body plan
Provide an example of a homeobox gene?
Pax6
If mutated can form blindness due to underdevelopment of retina
Suggests Pax 6 involved in development of eyes.
What are hox genes?
One group of homeobox genes only present in animals.
Responsible for correct positioning of body parts.
Found in gene clusters.
Humans = 39 hox genes.
How are living organisms laid out?
Symmetrical
Segmented –> specialised overtime to form specific functions
Order which genes appear along chromosome = order which effects are expressed in organism.
How are embryos developed?
Embryos divided into somites down vertebra
Each somite = different developmental job
Somites are directed by Hox genes to develop in particular way –> based on sequence
When expressed, hox genes act as transcription factors to turn on correct developmental genes
Describe role of apoptosis + mitosis in development:
Mitosis + differentiation = bulk of body
Apoptosis = refines parts by removing unwanted structures
—> also release chemical signals which stimulates mitosis + cell proliferation leading to remodelling of tissues
How to regulate mitosis + apoptosis?
Hox genes
Genes that control for M + A = switched on/off in appropriate cells.
.: Correct body plans develop
Response to internal/external stimuli
Drugs = affect activity of regulatory genes (thalidomide)
How does apoptosis occur?
DNA in nucleus + proteins in cytoplasm = degraded by enzymes
Mitochondria + cytoskeleton = broken down
Cell begins to shrink + break into fragments
‘Bleb’s develop on cell surface
‘Blebs’ engulfed by phagocytes + digested
What is epigenetics?
Heritable changes in gene function w/o changes to DNA base sequence
Caused by environment
Inhibit/promote transcription of genes by:
~ Modification of histones
~Methylation of DNA
Why is epigenetics useful?
Provide missing link on how environment changes cell w/o causing mutation to cause disease
Studies shown modifications passes through generations
–> associated with predisposing disease in offspring.
