Developmental Genetics Flashcards
What is the general function of maternal-effect genes? And another name for them?
Also called Egg-Polarity Genes
They extablish gradients from anterior and poterior poles of the egg
Maternal effect genes are totally under the control of the maternal genome, can be pre-fertilization
What are the segementation genes?
Gap Genes
Pair-Rule Genes
Segment-polarity genes
Expression is regulated by icoid and Nanos protein gradients
What is the function of gap genes?
They define broad regions in the egg (head, thorax…)
Mutation in it causes anterior segments to be deleted.
What is the function of pair-rule genes?
Defines 7 segments, defines individual segments
Mutation causes deletion of even numbered segments
What is the function of segment polarity genes?
Define 14 segments
Establishes polarity of the individual segments
Mutation - poterior half of each segment gets replaced with anterior half of adjacent segment
What are the homeotic genes? What are their function?
Antennapedia complex gene (head and thorax dev )and bithorax complex gene (posterior thorax and abdominal segment dev)
These determine regional characteristics
Activated of concentration of products of the segmentation genes
Contain homeobox
What are some egg polarity genes?
Establish dorsal/ventral axis: Dorsal, Cactus and Toll genes
Establish anterior-posterior axis: Bicoid, Nanos, and Hunchback
What is a morphogen?
A protein that varies in concentration and causes different developmental responces as a result of the concentration differences.
(E.g. Egg polarity genes)
Explain the breif function of the maternal effect genes responcible ble for the dorsal-ventral as well the blood
Dorsal gene - makes dorsal protein that concentrates on the ventral surface of embryo
Cactus protein - binds to dorsal protein trapping it in cytoplasm
Toll proteins - degrades cactus protein and dorsal protein moves into nuclei of ventral cells.
All maternally expressed in ovary.
Explain the maternal effect genes that are responcible for posterior - anterior axis?
Bicoid protein is for anterior structures. Stimulates hunchback
nanos gene - regulates expression genes responcible for posterior structures
-inhibits hunchback transcript translation
Hunchback - regulates transcription of gene for anterior structures.
What’s the difference between homeobox and homeodomain?
Homeobox is a segment of highly conserved DNA 180 nucleotides long
homeodomain is the protein made from the homeobox, 60 AA
What is the homeobox’s function?
Cranio-caudal segmentation along the basic axis of the body but also the organs.
Activated 3’ to 5’
Loss of function mutation - posterior to anterior transformations
Gain of function mutation - results in anterior to posterior transformations
Homeobox containing genes
T-box genes (Tbx)
Helix-loop-helix genes
Forkhead genes (Fox)
T-box genes effect on morphogenisis?
Inducing mesodermal germ later and coordination the outgrowth of the arm or leg
Helis-loop-helix genes effect on morphogenesis?
Coding for hlh transcription factors can hetero or homo dimerize and is important in myogenesis
