Genetic diseases

Question 1

List the type of mutation and clinical features: Down syndrome

Answer 1

Trisomy 21

Upslanting eyes
Epicanthic folds (upper eyelid fold)
Simian crease (1 palm crease across the hand)
Intellectual and growth retardation

Question 2

List the type of mutation and clinical features: Edward syndrome

Answer 2

Trisomy 18

Clubfeet and overlapping fingers

Question 3

List the type of mutation and clinical features: Patau’s syndrome

Answer 3

Trisomy 13

Small head and cleft palate

Question 4

List the type of mutation and clinical features:
Turner’s syndrome

Answer 4

Missing one X chromosome

Widely spaced nipples
Broad chest
Webbed neck
(generally less expressed female features in female)

Question 5

List the type of mutation and clinical features: Klinefelter’s syndrome

Answer 5

Extra X chromosome

Larger breast (males)
Testicular atrophy
(generally overexpression of female traits in a male)

Question 6

List the type of mutation and clinical features: Chronic myeloid leukemia

Answer 6

Translocation of chromosome 9 and 22 resulting in ABL-BCR fusion gene

Constitutively active RTK
Splenomegaly
Thrombocytopenia

Question 7

List the type of mutation and clinical features:
Beta thalassemia

Answer 7

Autosomal recessive - mutation in gene that makes beta-globulin, a component of hemoglobulin

Mild to severe anaemia
Hepatosplenomegaly

Question 8

List the type of mutation and clinical features: Cystic fibrosis

Answer 8

Autosomal recessive

Salty skin
Chronic respi and lung infections

Question 9

List the type of mutation and clinical features: Familial hypercholesterolemia

Answer 9

Autosomal dominant

Mutation results in body being unable to remove LDL

Question 10

List the type of mutation and clinical features: Achondroplasia + list another name of it

Answer 10

Autosomal dominant - mutation in FGFR3 gene affecting bone development

Also known as DWARFISM

Trident hands
Big head
Short limbs and bowed legs
Spinal lordosis

Question 11

List the type of mutation and clinical features: Osteogenesis imperfecta + list another name for it

Answer 11

Autosomal dominant

Also known as BRITTLE BONE DISEASE

Mutation results in abnormal collagen cross-linking and decrease type 1 collagen.

Frequent falls
Fragility fractures common

Question 12

List the type of mutation and clinical features: Huntington’s disease

Answer 12

Autosomal dominant

Cognitive decline, involuntary movement (chorea) and speech difficulties

Question 13

List the type of mutation and clinical features: DMD

Answer 13

X linked recessive

Reduced dystrophin production

Progressive muscle weakness and atrophy.
Calf hypertrophy
Scoliosis

Question 14

List the type of mutation and clinical features: G6PD

Answer 14

X linked recessive

Acute hemolytic anaemia
Jaundice
Pallor
Dark coloured pee

Question 15

List the type of mutation and clinical features: Colour blindness

Answer 15

X linked recessive.

Typically a mutation in red and green photoreceptors

Question 16

List the type of mutation and clinical features: Incontinentia pigmenti

Answer 16

X linked dominant

Mutation of NEMO gene

Hyper & hypopigmentation
Vesicular lesions
Cerebral atrophy
Cataracts and other eye defects
Pegged teeth

Question 17

List the type of mutation and clinical features: BCRA1/2

Answer 17

Breast and ovarian cancer that may or may not be familial

Suspect familial if young age onset and history of cancer in family

Question 18

List the type of mutation and clinical features: Huntington chorea

Answer 18

Dynamic mutation - mutation changes as it is passed down generations

Trinucleotide repeat disease
Uncontrollable dance like movements (chorea)

Question 19

List the type of mutation and clinical features: Prader Willis syndrome

Answer 19

Genomic imprinting - one copy is active one copy is silenced

Diminished muscle tone
Obesity
Thin upper lip

Question 20

List the type of mutation and clinical features: MELAS

Answer 20

Mitochondrial disease

Encephalopathy (dementia, stroke-like episodes, epilepsy), myopathy (short
stature) and lactic acidaemia (excess lactic acid in blood).

Question 21

Thalidomide as a teratogen

Answer 21

Underdeveloped limbs and face abnormalities.

Question 22

Alcohol as a teratogen, specifically ethanol

Answer 22

Fetal alcohol syndrome

Question 23

Explain the term: autosomal recessive

Answer 23

For an autosomal recessive trait or disorder to be expressed, an individual must inherit two copies of the recessive (disease-causing) allele (aa), one from each parent.

Individuals with one copy of the recessive allele and one copy of the dominant allele (Aa) are typically carriers and do not express the trait.

Question 24

Explain the term: autosomal dominant

Answer 24

The individual needs to inherit only one copy of the dominant allele (A) from either parent.

Question 25

Explain the term: X linked recessive

Answer 25

Males (XY) are more commonly affected by X-linked recessive disorders.

Male will be symptomatic and females likely carrier.

Affected father will pass to daughter but NOT SONS.

Affected mother may or may not pass it down.

Question 26

Explain the term: X linked dominant

Answer 26

Equally affects males and females as presence of one copy of the dominant allele on either X chromosome is sufficient.

Question 27

Explain the term: dynamic mutation

Answer 27

Refers to a genetic mutation characterized by a change in the number of repeating nucleotide sequences within a gene. It is often associated with tandem repeat sequences, where a short DNA sequence is repeated multiple times in a row.

Question 28

Explain the term: genomic imprinting

Answer 28

Certain genes are ‘imprinted’ during gamete formation (either from the father or mother) and that marked gene influences how genes are expressed in the offspring

Question 29

Explain the term: inborn errors of metabolism

Answer 29

IEM are genetic disorders that result from mutations in genes encoding enzymes or proteins involved in metabolic pathways – leading to accumulation of toxic
substances or deficiencies in essential products.

Question 30

When will autosomal recessive manifest and not manifest?

Answer 30

Yes: Homozygous recessive

No:
Homozygous dominant
Heterozygous (carrier)

Question 31

When will autosomal dominant manifest and not manifest?

Answer 31

Yes:
Homozygous dominant
Heterozygous

No: Homozygous recessive

Question 32

Explain the term: variable expression

Answer 32

Range and severity of features in individuals with the same genetic condition.

Variable expression means the disease has penetrated = manifested

Question 33

Explain the term: variable penetration

Answer 33

Presence or absence of clinical symptoms in individuals carrying the same genetic mutation and hence genetic condition.

Question 34

Explain the term: genetic counselling

Answer 34

The process of providing information, support, and guidance to individuals or families regarding the risk, impact, and management of genetic conditions or the likelihood of passing them on to future generations