Genetics Flashcards
What does Mendelian genetics mean
More dominant gene reflected in phenotype
What are deletions
A position of a chromosome missing
Very rare
E.g Cri du chat syndrome
What are duplications
A portion of a chromosome is duplicated
E.g Charcot-Marie-Tooth syndrome
What are translocations
Portion of one chromosome directly swapped with another
Often does not directly lead to any syndromes
What is trisomy
Having an extra chromosome
Down’s syndrome: trisomy 21
Patau syndrome: trisomy 13
Edward’s syndrome: trisomy 18
What is mosaicism
Chromosomal abnormality after conception
Happens in a portion of the cells of the body
Have different genetic material in different parts of the body
What is mitochondrial inheritance
Aka maternal inheritance
Paternal mitochondria are in tails of sperm, so do not enter egg
What is the genetic abnormality in Down’s syndrome
Trisomy 21
What are the physical features of Down’s syndrome
Hypotonia
Brachycephaly (small head with flat back)
Short neck
Short stature
Flattened face and nose
Prominent epicanthic folds (skin overlying medial portion of eye and eyelid)
Upward slope of palpable fissure (gap between upper and lower eyelid)
Single palmar crease
What are the complications of Down’s syndrome
Learning disability
Recurrent otitis media
Deafness (eustachian tube abnormality)
Visual problems (myopia, strabismus, cataracts)
Hypothyroidism
Cardiac defects
Atlantoaxial instability
Leukaemia
Dementia
What is the antenatal combined test for Down’s syndrome
Between 11 and 14 weeks
Nuchal translucency on ultrasound
Bloods (beta-HCG, PAPPA)
What is the antenatal triple test for Down’s syndrome
Between 14 and 20 weeks
Bloods (beta-HCG, AFP, serum oestriol)
What is the antenatal quadruple test for Down’s syndrome
Between 14 and 20 weeks
Bloods (beta-HCG, AFP, serum oestriol, inhibin-A)
What is the management for Down’s syndrome
Supportive care from MDT
Regular thyroid checks
ECG to diagnose cardiac defects
Regular audiometry
Regular eye checks
What is the genetic abnormality in Klinefelter syndrome
Males have extra X chromosome
47 XXY
What are the physical features of Klinefelter syndrome
Develop at puberty
Taller height
Wider hips
Gynaecomastia
Weak muscles
Small testicles
Reduced libido
Shyness
Infertility
Subtle learning difficulties
What is the management for Klinefelter syndrome
Testosterone injections
Advanced IVF techniques
Breast reduction surgery
MDT management
What is the prognosis for Klinefelter syndrome
Life expectancy close to normal
Slightly increased risk of: breast cancer, osteoporosis, diabetes, anxiety, depression
What is the genetic abnormality in Turner syndrome
Females with only one X chromosome
45 XO
What are the physical features of Turner syndrome
Short stature
Webbed neck
High arching palate
Downward sloping of eyes with ptosis
Broad chest with widely spaced nipples
Cubitus valgus (exaggerated angle of elbows)
Underdeveloped ovaries with reduced function
Late or incomplete puberty
Mostly infertile
What are the conditions associated with Turner syndrome
Recurrent otitis media
Recurrent UTIs
Coarctation of the aorta
Hypothyroidism
Hypertension
Obesity
Osteoporosis
Learning disability
What is the management of Turner syndrome
Growth hormone therapy (prevent short stature)
Oestrogen and progesterone replacement (establish secondary sexual characteristics)
Fertility treatment
Monitoring for associated conditions
What is the pattern of inheritance for Noonan syndrome
Autosomal dominant
What are the physical features of Noonan syndrome
Short stature
Broad forehead
Downward sloping eyes and ptosis
Wide space between eyes
Prominent nasolabial folds
Low set ears
Webbed neck
Widely spaced nipples
