Genetics Flashcards
Clinical features of Downs Syndrome
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Define congenital defect
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Subdivisions of congenital defects
- Single
- Multiple
Single congenital abnormalities
- Malformation
- Disruption
- Deformation
- Dysplasia
Multiple congenital abnormalities
- Sequence
- Syndrome
- Association
Malformation
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Disruption
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Deformation
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Dysplasia
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Syndrome
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Sequence
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Association
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Aneuploidy of Patau Syndrome
Trisomy 13
Aneuploidy of Edward’s Syndrome
Trisomy 18
Aneuploidy of Downs Syndrome
Trisomy 21
Clinical features of Downs Syndrome
Newborn: -hypotonia (floppy baby syndrome=decreased muscle tone) -lethargy -excess nuchal skin Craniofacial: -macroglossia (abnormally large tongue) -small ears -epicanthic folds (vertical fold of skin from the upper eyelid that covers the inner corner of the eye) -brushfield spots (tiny white spots around the iris of the eye) Cardiac: -septal defects -atrioventricular canal Limb: -single palmar crease -sandal gap (wide gap between the first and second toes) Other: -short stature -duodenal atresia -low IQ but advanced social skills
Three different chromosome aberrations leading to Downs Syndrome
1) Trisomy 21 (in 95% of cases)
2) Translocation (Robertsonian specifically and in 4% of all cases)
3) Mosaicism (1% of cases=abnormal cell population in the body)
Clinical features of Patau’s Syndrome
Brain problems: -Holopresencephaly (structural malformation of the brain which often affects facial features giving a cleft lip and orbital hypotelorism) -mental retardation Cardiac problems: -septal defects -patent ductal arteriosus
Clinical features of Edward’s Syndrome
Brain problems: -mental retardation Cardiac problems: -septal defects -patent ductal arteriosus Digestive tract defects: -Oesophageal atresia (upper part does not connect with lower part and stomach) -Omphalocele (infants intestine or other abdominal organs are outside the body because of a hole in the belly button area) Kidney malformations: -Horseshoe kidney
Example of autosomal dominant disorder
Huntington’s disease
Example of autosomal recessive disorder
Cystic fibrosis
Example of X-linked recessive disorder
Haemophilia
Prader-Willi Syndrome
- Chromosome 15 imprinting disorder
- paternal chromosome loses function (P=paternal)
Angelman Syndrome
- Chromosome 15 imprinting disorder
- maternal chromosome loses function
Clinical features of Prader-Willi Syndrome
Brain problems: -mental impairment (average IQ is 60-70) -behavioural problems Limb problems: -muscle hypotonia -short stature -small hands and feet Other: -delayed/incomplete puberty -infertility -hyperphagia (abnormal appetite and excessive ingestion of food)=leads to marked obesity
Clinical features of Angelman Syndrome
- Seizures (seen in more than 80% of patients, seizures have an early onset of less than 3 years of age)
- microcephaly (baby’s head circumference is a lot smalller than normal, abnormal head smallness compared to the size of the rest of the body)
- severe developmental delay
- speech impairment (poor or absent speech)
- gait ataxia
- behavioural uniqueness
MELAS (mitochondrial disorder)
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LHONS (mitochondrial disorder)
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Aims of prenatal testing
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Prenatal tests=Scanning
- Ultrasound
- Fetal MRI
- Fetal cardiac scan (ultrasound)
Prenatal tests=non-invasive
- maternal serum screening
- cell free fetal DNA (NIPT)
Prenatal tests=invasive
- Chorionic villus sampling (CVS)
- Amniocentesis
Reproductive options available
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Egg and sperm donation
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Adoption
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Pre-implantation genetic diagnosis
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Clinical features of MELAS
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Clinical features of LHONS
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Three parent babies
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Explain mitochondrial inheritance
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Phenylketonuria (PKU)
-inborn error of metabolism
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Clinical features of PKU
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Therapeutic management of PKU
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Medium chain Acyl-CoA dehydrogenase deficiency (MCADD)
-inborn errors of metabolism
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Clinical features of MCADD
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Therapeutic management of MCADD
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Oncogenes
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Tumour Suppressor genes
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