Embryology – Complications of development Flashcards
What proportion of Mal-development causes are genetic, environmental and multifactorial
Genetic – 30%
Environmental – 15%
Multifactorial – 55%
What occurs in multiple pregnancy
Identical twins / triplets: one conceptus forms 2 / 3 inner cells masses to form 2 / 3 genetically identical individuals
What is chimerism
Chimerism: 2 genetically distinct conceptuses combine to form one individual
Fused multiple zygotes
Non-identical zygotes
What is mosaicism
Non-Disjunction
Differences between cells within one individual
Which gene codes for eye colour and explain its development
Human chromosome 15.
Brown most common colour; others mostly in Caucasians.
Differentiation of eyes begins about Day 22 Post-fertilisation
Event must predate Day 22.
Give an example of a XY-linked chromosomal disorder where there are too many chromosomes
Kleinfelter’s syndrome (XXY). Decreased fertility
Which chromosomes are involved in Down’s syndrome and what determines survival
chromosome 21
Heart problems determine survival.
Which chromosomes are involved in Edward’s syndrome and what determines survival
Chromosome 18
Most die before birth
Those that live do so <2 weeks
Which chromosomes are involved in Patau’s syndrome and what determines survival
Chromsome 13
Most die before brith
80% that live die within a year
Give an example of XY linked chromosomal disorders where there are too few and describe it
Turner’s syndrome
X0
Female, short stature, infertile
What is caused by Y0
Not viable
Describe autosomal chromosomal losses
No complete losses are viable
Partial chromosome loss syndromes known and characterised
What are autosomal translocations associated with
Development of tumours, lymphoma, leukaemia and sarcoma
Which trisomy has never been detected in pregnancy loss tissues
Ch1
Describe Holt-Oram syndrome
Phenotype due to mutation in TBX5 which is required for devleopment of both heart and hands
Heart/hand defects
Atrial septation defects
Range of hand abnormalities
