Genetics Flashcards
Name 3 diseases with AD inheritance.
- ADPKD.
- HD.
- Marfan’s.
Give 6 characteristics of AD inheritance.
- both homozygotes and heterozygotes manifest disease (there is no carrier state)
- both males and females affected
- only affected individuals can pass on disease
- disease is passed on to 50% of children
- normally appears in every generation (although see below)
- risk remains same for each successive pregnancy
Give 3 characteristics of AR inheritance.
- Both parents must be carriers.
- Often only one generation is affected.
- 2 carrier parents have a 1 in 4 risk of having an unaffected child.
Name 3 diseases with AR inheritance.
- CF.
- Sickle cell.
- Haemochromatosis.
Give an example of an X linked recessive disease.
Duchenne and Becker muscular dystrophy.
Give 3 characteristics of X linked inheritance.
- Male > female affected.
- No male to male transmission.
- Each male child of a heterozygous female carrier has a 50% chance of being affected whilst each female child of a heterozygous female carrier has a 50% chance of being a carrier.
Give 4 examples of non-mendelian inheritance.
- Multifactorial e.g. neural tube defects.
- Mitochondrial.
- Genomic imprinting.
- Gonadal mosaicism.
What is gonadal mosaicism?
Gonadal mosaicism is when there are two different populations of cells in the gonads. One population is normal and the other is mutated. All gametes from the mutated line are affected.
What are the cardiac complications of Down’s syndrome?
- endocardial cushion defect (most common, 40%, also known as atrioventricular septal canal defects)
- ventricular septal defect (c. 30%)
- secundum atrial septal defect (c. 10%)
- tetralogy of Fallot (c. 5%)
- isolated patent ductus arteriosus (c. 5%)
What are some other complications on top of cardiac ones in Down’s syndrome?
- subfertility: males are almost always infertile due to impaired spermatogenesis. Females are usually subfertile, and have an increased incidence of problems with pregnancy and labour
- learning difficulties
- short stature
- repeated respiratory infections (+hearing impairment from glue ear)
- Increased risk ofacute lymphoblastic leukaemia
- Increased risk of hypothyroidism
- Alzheimer’s disease
- Risk of atlantoaxial instability
- Epilepsy
List 4 features of Patau Syndrome (trisomy 13).
Microcephalic, small eyes
Cleft lip/palate
Polydactyly
Scalp lesions
List 4 features of Edward’s syndrome (trisomy 18).
Micrognathia
Low-set ears
Rocker bottom feet
Overlapping of fingers
List 5 features of Fragile X.
Learning difficulties Macrocephaly Long face Large ears Macro-orchidism
List 4 features of Pierre-Robin syndrome.
Micrognathia
Posterior displacement of the tongue (may result in upper airway obstruction)
Cleft palate
List 3 features of Prader-Willi syndrome.
Hypotonia
Hypogonadism
Obesity