Fetal Abnormalities I: Genetics Flashcards
What are the three kinds of genetic disorders, w/ regard to scale/location of disorder?
- Chromosomal (whole chromosome)
- Monogenic
- Complex (polygenic etc.)
The study of chromosomes (as opposed to genes) is called…
Cytogenetics
The two broad classes of chromosomal abnormalities are…
- Structural
- Numerical
What is polyploidy? Triploidy? Tetraploidy?
Poly: more than two sets of chromosomes
Tri: one extra sets of chromosomes
Tetra: 2 extra sets of chromosomes
Triploidly consequences
- Most are miscarried by first trimester
- As pregnancy progresses, survival gets lower and lower
- Even if born alive, only lasts around ~1 month avg
Sonographic features of triploidy
- Omphalocele (what is that?)
- Micrognathia (what is that?)
- CNS abnormalities
(bottom to top, 3 of them = tri)
What are the two mechanisms that lead to triploidy?
- Two sperm fertilise one egg (what prevents this, usually?) All are haploid. (Type I -> all have onen genome)
- Haploid sperm fertilises diploid egg (type 2 -> egg has 2n genome)
Similarities/differences between digynic and diandric triploidy
Similarities:
- Both Oligohydramnios (what is this?)
- Both can cause IUGR
Differences:
- Paternal causes normal head, symmetrical, large placenta
- Maternal causes asymmetrical, large head, small placenta
(Pacenta size proportionial to attractiveness; male wins)
What are the most common kinds of aneuploidy?
- Trisomy 13 , 18, 21 (what are each called?)
- XXX, XXY, XYY
True or false - if Chloe has one child with Patau’s syndrome, she’s at increased risk of other trisomic complications
True. Not good
Clinical features of down syndrome
- Short stature
- Face: low ears, wide eyes, flat nose bridge
- Single palmar creases
- Mental retardation and increased coronary heart disease
Sonographic features of Edward’s Syndrome
- Rocker bottom feet
- Omphalocele
- Micrognathia
- Congenital heart defects
Clinical features of Patau’s Syndrome
- Rocker bottom feet
- Omphalocele
- Congenital heart disease
(Bdubs no Micrognathia)
What are the consequences of Turner’s Syndrome, both before and after birth (incl. sonographic)
- Before birth, 98% of conceptuses die
- Sonographic: left-sided heart disease, ascites (like HF)
- After birth: short stature, webbed neck, failure of ovaries to develop, outward turning elbow
Clinical features of klinefelter syndrome
- Low T
- Reduced muscle mass
- Gynaecomastia
- Infertile
What is non-alleilic homologous recombination
- homologous recombination (crossing over) that occurs between two chromosomes that ARE NOT alleles
- e.g. two similar sections, one on chromosome 4, and one on chromosome 8
Balanced vs unbalanced structural chromosome abnormalities
- Balanced: no net loss or gain of genetic material (e.g. translocation, SNPs)
- Unbalanced: net change in amount of genetic material (e.g. microdeletions)
3 features of DiGeorge Syndrome
- Cardiac defects
- Cleft palate
- Learning difficulties
Features of Wolf-Hirschhorn Sundrome
- Mental retardation
- Microcephaly
- broad nasal bridge
Cri du Chat Syndrome features
- Mental retardation
- Cat-like cry
- Microcephaly
(Chat = Cat)
Angelman Syndrome Fx
- Hypotonioa
- Seizures
- Inappropriate happy behaviour
Prader-Willi Syndrome features
- Hyperphagia -> obesity
- Small hands and feet
- Almond shaped eyes
