Teratology Flashcards
Top 2 causes of infant mortality (up to age 4)
Birth defects
Preterm/Low birthweight
What % of zygotes and pregnancies result in normal, healthy babies?
25% zygotes
<50% pregnancies
Gestational milestones in order
Implantation Primitive streak Early Differentiation Organogenesis Ends Usual Parturition
When does birth defects start in gestation?
Primitive streak onwards
6 weeks
Why do you have to know the gestational period of a women before giving pills?
primitive streak (6 weeks) to organogensis end (50 weeks) is birth defects
Intercellular Signals
Message sent by inducer Spatial proximity received by compentent population ∆ developmental state Maturational or stability
What allows for internal rearrangement in humans?
We have time in gestation, development schedules, populations of cell
What is the dynamic nature of embryonic development?
There is a small period of time to go back before going forward
Ability to adjust to changing conditions
How much do we not know about the cause of birth defects?
50%
developmental plasticity
ability of a single gene to express +1 phenotype based on environmental conditions
(BMI >27; T2D, CHD)
Reason to advocate early prenatal care
What causes chromosomal abnormaities typically?
nondisjunction during gametogenesis
How much ova are aneuploid in humans mostly?
15%, increases in maternal age
How else can aneuploid happen?
nondisjunction during cleavage: results in mosaicism of zygote
Signs of Trisomy 21/Down Syndrome
Brachycephaly
flat nasal bridge
upward slanding palpebral fissures
Simian crease
Fatality in Trisomy 21/Down Syndrome
75% spontaneous abort
20% still born
Survivors survive into 50’s
Trisomy 18/Edward Syndrome Signs
Flexed digits
Micrognathia
Low set, malformed ears
prominent occiput
Fatality in Trisomy 18/Edward Syndrome
50% spontaneously abort
survival rarely past 6 month
Signs of Patau Syndrome/Trisomy 13
Cleft lip/palate
Sloping forhead
CNS malformations
Polydactyly
Fatality of Patae Syndrome/Trisomy 13
50% spontaneously abort
Rarely survive beyond 6 months
Signs of Turner syndrome/45, X
Lymphedema
Lack of secondary sex characteristics
Webbed neck
broad chest
Fatality of Turner Syndrome/45, X
1% embryos survive
X missing in Turner’s syndrome
Paternal X usually
47, XXX
Normal female appearance
fertile
20% mentally retarded
47, XXY/Klinefelter Syndrome
Male small testes aspermatogenesis long legs intelligence deficit gynecomastia
47, XYY
Normal male appearance
tall
Triploidy 3N
Intrauterine growth retardation
Small trunk
large head
What typically causes triploidy 3N
dispermy
Fatality of triploidy 3N
live births are extremely rare
Tetraploidy 4N
Abort very early
probs due to failure of cytoplasmic cleavage or chromosomal segration at first mitotic cleavage division
Nonhomologous DNA translocation caused by
radiation, drugs, chemicals, viruses
balanced vs unbalanced translocation
balanced: non DNA lost or added - less severe
unbalanced - more severe
Cri du chat syndrome
deletion of short arm of chromosome 5
Cri du chat syndrome or deletion of short arm of chromosome 5 results in
microcephaly
severe mental retardation
heart anomalies
Duplications can exist as (3)
- Tandem repeat within chromosome
- attached to a chromosome
- As a separate fragment
Duplications compared to deletions
More common
Less harmful
Inversions
Segment of chromosome is reversed
2 types of chromosomal inversion
ParAcentric: single arm
Pericentric: both arms, including the centromere
What happens in inversion
interes with homolgous recombination and segration during meiosis
Isochromosomes
centromere divides dransversely intead of longitudinally
Most common structural defect of X chromosome
Isochromosomes
When can mutations not be deliterious?
When good (evolution) When silent: no effect on protein function or impair function of a redundant gene
What disease has a problem with sonic hedgehog?
Holoprosenscephaly
What happens in holoprosencephaly?
Failure of forebrain to completely separate into 2 lobes
leads to a wide range of brain, skull and facial defects
(form cleft lip to cyclopia/hypertolorism with proboscis)