developmental genetics Flashcards
when does gastrulation occur
14-28 days
what is gastrulation
rearrangement of a single layer into a trilaminar structure
trilaminar structure of gastrulation?
ectoderm, mesoderm, and endoderm
what major structural feature forms in the gastrulation phase
primitive streak
neurlation?
folding process that turns the nueral plate into the neural tube
what type of birth defects does neurlation cause
neural tube defects
where does neurulation close at
5 diff sites
what does the ectoderm separate into during neurlation
neural tube, epidermis, and neural crest cells
when is the mesoderm formed
gastrulation
what does the notochord do?
induce neural tube and body axis
what does the dorsal mesoderm give rise to?
axial skeleton, skeletal muscle, and CT
what does the intermediate mesoderm give rise to?
kidneys and GU
what does the lateral mesoderm give rise to?
heart, viscera, body wall
what does the mesoderm consist of
notochord, dorsal mesoderm, intermediate mesoderm, lateral mesoderm, and head mesenchyme
what layer of the trilamina causes many birth defects
mesoderm
what does the endoderm form
lining of digestive tract, respiratory tree, middle ear, thymus, thyroid, and parathyroids
purpose of primitive streak
crate A/P axis
what does nodal expression do
initiates and maintains primitive streak
purpose of Hox genes
position cells and tissues
mutations in Hox genes leads to…
abnormalities of limb formation
what is situs solitus
normal axis formation
what is situs inversus
body is a mirror image- appendix on left side
what is situs ambiguous/heterotaxy
same on both sides ex: left and right lung both have 3 lobes
what is craniofacial development regulated by
Hox genes
1st MC birth defects? 2nd MC birth defects?
heart then limb
what embryonic later is limb formation derived from
mesoderm
what influences distal progression of limb
apical ectodermal ridge
what does the Apical ectodermal ridge stimulate proliferation of
mesodermal cells
what does the zone of polarizing activity specify
anterior and posterior information
what is key for thumb/finger differentiation
zone of polarizing activity
what occurs in Holt Oram Syndrome
malformations in radial, thenar, and carpal bones, congenital heart disease, cardiac conduction disease
what side of the body is Holt Oram Syndrome more severe in
left
what type of congenital heart defects do ppl with Holt Oram Syndrome have
ASD and VSD
what can cardiac conduction disease progress to
complete heart block with or without atrial fibrillation
what gene is the mutation on in holt oram synd
TBX5
organ formation?
Common cells and tissues “collaborate” for a unified function
what is skeletal formation dependent upon
osteoblasts
what is skeletal formation regulated by
transcription factor RUNX2
what do RUNX2 mutations cause
cleidocranial dysostosis
clinical features of cleidocranial dysostosis
Open fontanelle, Hypertelorism, Absent clavicles
what do PAX 6 gene mutations cause
aniridia (no iris)
what do Pax 6 gene mutations cause
small eye
ectopic expression?
Can manipulate the gene to express in a different location
example of ectopic expression?
pax 6 mutations
what are malformation defects due to
Defects due to intrinsically abnormal development
how do malformations arise
genetic, teratogens, and fetal environment
examples of syndromes with malformations?
TAR syndrome
Fanconi anemia
Polydactyly
what are deformation defects due to
nondisruptive mechanical force, resulting in abnormal form or position; extrinsic factor
what causes deformations
Uterine constraint
Malformation or disruption may contribute
how is the prognosis for deformations
good! spontaneous resolution and internal fixation
examples of syndromes with deformations?
plagiocephaly, metatarsus adductus (clubfeet)
when do deformations occur
Post-conception!