Genetics Flashcards
(41 cards)
What is the genotype ?
Refers to the genes that we have. For example - having the gene that codes for brown eyes.
What is the phenotype ?
Refers to the physical expression of the genes that we have. For example - actually having brown eyes
What is a chromosome disorder ?
A condition where there is either a structural abnormality, an extra abnormal position or an abnormal number of chromosomes compared to normal.
What are deletion disorders ?
Occur where a portion of a chromosome is missing.
What are duplication disorders ?
They occur where a portion of a chromosome is duplicated.
The chromosome contains twice the number of copies of that gene.
What is a translocation disorder ?
Occurs when a portion of one chromosome is directly swapped with a portion of another chromosome. The swap can be balanced ( reciprocal ) or not balanced ( nonreciprocal ).
What is robertsonian translocations ?
Occurs in acrocentric chromosomes.
These chromosomes are 13, 14, 15, 21 and 22.
They loose the short arm completely and the 2 long arms connect to each other at the centromere essentially loosing a chromosome when they rid of the 2 short arms.
What is trisomy ?
Where the person has an extra chromosome. They have 3 copies of a particular chromosome.
What is patau syndrome ?
This is trisomy 13.
Patients have dysmorphic features, structural abnormalities and learning disability.
What is a characteristic feature of patau syndrome ?
Rocker bottom feet where the soles of the feet are convex ( rounded outwards ) in shape
What is Edwards syndrome ?
This is trisomy 18.
Dysmorphic features and learning difficulties
Rocker bottom feet
Which parent does a patient with a mitochondrial disorder inherit it from ?
Mother
What is diagnostic testing - genetics ?
Diagnostic testing involves testing a foetus or a person for a suspected genetic condition.
This is tested for via amniocentesis.
What is predictive testing ?
Involves testing a person for a specific gene mutation that has implications for them in the future. Examples - BRCA1 breast cancer gene
What is carrier testing ?
Involves testing parents or potential parents for the gene for a specific autosomal recessive condition in order to calculate the risk of passing it to their children.
What is karyotyping ?
Involves looking at the number of chromosomes, their size and basic structure.
This is helpful in diagnosing conditions like Down’s syndrome and Turner syndrome
What is microarray testing ?
Involves cutting up the genetic material from an individual using enzymes.
What is Down’s syndrome ?
Caused by 3 copies of chromosome 21.
How does Down’s syndrome present ?
Hypotonia ( reduced muscle tone )
Brachycephaly ( small head with a flat back )
Short neck
Short stature
Flattened face and nose
Prominent epicanthic folds
Upward sloping palpebral fissures
Single palmar crease
What is epicanthic folds ?
Folds of skin covering the medial portion of the eye and eyelid.
What are some complications of Down’s syndrome ?
Learning difficulty
Recurrent otitis media
Deafness - glue ear and conductive hearing loss
Visual problems - myopia, strabismus and cataracts
Hypothyroidism
Cardiac defects - ASD, VSD, patent ductus arteriosus and tetralogy of fallot
Leukaemia
Dementia
What are some antenatal screening for Down’s syndrome ?
Combined test - USS + maternal blood test
Triple test - involves beta-hcg, AFP and serum oestriol
What testing is done antenatally when suspecting Down’s syndrome ?
Chorionic villus sampling
Amniocentesis
What are some regular follow ups for someone with Down’s syndrome ?
Regular thyroid check ( 2 yearly )
Echocardiogram
Regular Audiometry
Regular eye checks
