Genetics Flashcards
On a pedigree chart what does the double line joining mean?
Consanguinity
On a pedigree chart, if you are unsure on the sex what do you represent the individual as? what if they are in utero?
diamond
P
How do you represent twins on a pedigree chart?
oblique line from generation above and joined with a double horizontal line
How many chromosomes, genes and base pairs do we have in each cell?
23 chromosomes, 23000 genes, 3.3 billion base pairs
Mitochondrial inheritance is passed how?
exclusively maternal
Example of cytogenetic testing?
FISH testing
Example of Molecular testing
DNA analysis - microarray, gene panels, exomes, whole genome
What is array CGH? what is it used for?
microarray comparative genome hybridisation
Used for chromosomal microdeletions
Features of Down’s Syndrome?
Single palmar crease Clustered facial features Stubby digits Small ears Slightly slanted eyes Sparce hair hypotonia Large tongue Small nose
What does nondisjunction mean in regards to cell division?
When some chromosomes dont make it to the right side of the cell
Apart from nondisjunction of chromosome 21, what is the other cause of Down’s Syndrome caused by abnormality in cell division?
Translocation of 21 onto 14 in mothers haploid
What is risk of reoccurence in trisomy 21 vs translocation of 21
trisomy = less than 1% Translocation = 50%
What trisomy causes Patau?
13
What brain abnormality occurs in Patau and how does this present at birth?
Hypotelorism - front of brain fused
Seizures
What defects does an individual with Patau syndrome suffer from?
Seizures Heart defect Renal dysplasia IUGR Polydactyly Early death
Where is the DiGeorge microdeletion and how is it diagnosed?
22q11 deletion diagnosed with microarray
What abnormalities do people with DiGeorge usually suffer from?
Cardiac abnormalities Thymus hypoplasia - hypocalcaemia, t cell dysfunction, infection Small chin Weird lips Broad nasal base Cleft palate Small sticky out ears
47 XXY? 47 X? Trisomy 18?
Kleinefelter
Turner
Edwards
Williams Syndrome deletion? what heart defect?
7q11 - supravalvular ventricular stenosis
Prader-Willi deletion?
15q11
Difference between Prader Willi and Angelman Syndrome?
Prader Willi is if its inherited from the male and Angelman is if its inherited from the female
List 6 types of gene disorder transmission?
Autosomal dominant, recessive, xlinked dominant, recessive, y linked, mitochondrial
Marfans:
Inheritance pattern?
What gene is effected? on what chromosome?
What do you measure between in Marfans to work out if there is a reduced ratio?
Features?
autosomal dominant
fibrillin gene on chromosome 15 (FBN1)
Measure symphysis pubis to head and syphysis pubis to toes then ratio will be less than 0.8
Lax joints, arachnodactyly, ectopic lentis (blind), dissection of aorta, high arched palate
2 specialties that need to see individuals with Marfans
cardiology and ophthalmology
What drug class can partially protect against aortic aneurysm in Marfans?
Sartans
What chromosome is effected in NF1?
17
What are 3 signs of NF1?
Macrocephaly, cafe au lait spots, lisch nodules
What chromosome is NF2 found on?
22
What is NF2 associated with?
meningiomas, schwannomas
Tuberous sclerosis is associated with what presentation?
Ash leaf hypopigmentation
Facial angiofibromas
Epilepsy
Cortical tumours
What does the term anticipation refer to in Huntingtons Disease?
Gets worse throughout the generations
How many triplet repeats are enough to cause Huntingtons
35 and above
What chromosome is effected in Huntington’s?
4
Name 3 conditions that are caused by triplet repeat expansions?
Huntingtons
Myotonic dystrophy
spinocerebellar ataxia
What blood test will be very abnormal in DMD?
Very high CK
What investigation will be needed in DMD? what is it looking for?
Muscle biopsy looking for dystrophin protein
Gower Manoeuvre in DMD?
crawl, use hands to prop up, grasp onto knees
Features of FAS?
thin upper lip small palpebral fissures small nose small mouth prominent veins learning difficulties Smooth long philtrum
How does the trimester in pregnancy that you drink alcohol effect the cognitive and physical differences in FAP?
Early in pregnancy effects physical appearance
Late in pregnancy effects cognitive development
Which vitamin is teratogenic in pregnancy?
Vitamin A
Whcih anticoagulant is teratogenic in pregnancy?
Warfarin
What does contiguous gene inheritance refer to?
duplications or deletions of multiple genes on a chromosome
What is achondroplasia the most common cause of?
Dwarfism
What are the shape of the vertebrae in achondroplasia?
Bullet shape
Osteogenesis imperfecta?
numerous fractures, IUGR, wormian bones
What is a symptom in the eyes of Down Syndrome children?
Brushfield
Diagnosis for duodenal atresia and what is usually seen? What is there usually a history of?
Xray and double bubble
Polyhydramnios
Most common heart defect in Down Syndrome?
AVSD
What is the name of the mutation that can lead to Down Syndrome that is not resultant in trisomy 21?
Balanced Robertsonian translocation
What departments do Down Syndrome children need to be referred to?
OT SLT Opthalmology ENT - hearing Child development team Cardiology
Why do children in Down Syndrome suffer ear troubles? what ear troubles are common? How is this monitored?
Increased rate of middle ear infections
Common to have both conductive and sensorineural deafness
Routine ENT follow up
What 2 conditions can develop in Down Syndrome patients and therefore screened for every 2 years?
Hypothyroidism
Coeliac disease
Apart from leukaemia what are Down Syndrome patients more likely to suffer with?
Early onset Alzheimers
Obstructive sleep apnoea
Atlantoaxial instability
