Genetics Flashcards by Dasun Dias

Karyotype of Down syndrome

Trisomy 21

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T/F
Blank facial expression is common in Down syndrome

False

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Typical features in Down syndrome

Microcephaly
Low, flat nasal bridge
Oblique upward- slanting eyes
Low set ears
Short nose
Open mouth
Large protruding tongue
Single palmar crease
Saddle gap
Hypotonia
Hepatosplenomegaly

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Down syndrome is associated with (complications)

Leukemia- Hepatosplenomegaly
Anal abnormalities
Duodenal atresia
Hirschsprung disease
Developmental delay
Hypothyroidism

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The growth chart used in down syndrome

Down syndrome specific growth chart

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Ways how trisomy 21 occurs in down syndrome

Non- disjunction (95% of the cases)
Translocation 4%
Mosaicism 1%

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Risk of recurrence of Down syndrome is highest in

Translocation ( 21:21 translocation is 100%)

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Low- set ears

At least 1/3 of the ear doesn’t protrude out from an imaginary line drawn from the outer corner of the eye and the eye

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confirmatory test in Genetic disorders

Karyotyping

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Referrals that should be done for Down syndrome

Cardiology

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Steps of Mx if there’s a developmental delay in down syndrome

Refer to rehabilitation programs
Physiotherapy
Speech therapy
Hearing assessment
Visual assessment

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Mx of down syndrome

1.Karyotyping - confirm the Dx
2.Ix for possible complications( Echo, USS Abd, CBC, Blood picture, Thyroid function test)
3.Growth and development assessment
4.Thyroid supplementation ( if hypo)
5.Refer to a cardiologist ( if cardiac issues)
6.Refer to a special school
7.If there’s a growth delay - refer to rehabilitation programs
8. Genetic counselling to parents

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2nd Most common trisomy

Edward syndrome

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Edward syndrome is most seen in males/females?

females (80%)

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T/F
Majority of edward syndrome will be stillbirths

True

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Reason for low survival rate in Edward syndrome

Heart abnormalities
Kidney malformations

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Sx of Edwards Syndrome

Small head
malformed ears
Widely- spaced eyes
Clenched hands
low set ears
overlapping fingers

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Widely- spaced eyes?

gap between the two eyes is more than the gap for one eye

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Sx of patau Syndrome

Small head
Cleft lip/ palate
Absent eyebrows
Dysplastic/ malformed ears
Clenched hands
Polydactyly
Undescended or abnormal testes

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Karyotype of Patau syndrome

Trisomy 13

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Turner syndrome karyotype

45 chromosomes. XO

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Most cases of turner syndrome is diagnosed late. When?

When performing tests for being unable to get PG

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Hormone deficiencies in Turner syndrome

Reduced GH
Reduced estrogen
Reduced Thyroxine

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Sx of turners

Short stature
Low posterior neckline
Webbing of neck
Shield chest
Edema of dorsum of hands and feets
Cubitus varus
Rudimentary ovaries, uterus
Cardiac abnormalities

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shield chest is seen in

Turner syndrome - widely spaced nipples

low set ears are seen in

Down syndrome Edward syndrome

How is the cognition in turner syndrome

Mostly normal

Mx of turner syndrome

Educate the parents- genetic counselling Refer to a cardiologist Hormone replacement therapy Family planing advices

Common cardiac complication associated with turner

CoA

Cubitus varus seen in

Turner syndrome

Saddle gap is seen in

Down syndrome

3 GIT conditions associated with Down syndrome

Duodenal atresia Hirschsprung disease

Klinefelters syndrome karyotype

44 XXY

Klinefelter syndrome presents as male/female

both males and females

# Klinefelter Syndrome Epidemiology

1 in 500 to 1000 births

# Klinefelter Syndrome Males are usually sterile (T/F)

# Klinefelter Syndrome Sx

* Youthful build * Rounded body type- feminine fat distribution * Some degree of gynecomastia * Hypogonadism * Both male and female features * No bitemporal baldness * Taller than average height * Reduced facial, body hair * Osteoporosis risk high * Small testes- atrophy

# Klinefelter Syndrome IQ

generally poor

# Klinefelter Syndrome They are generally attracted to males/ females?

not generally attracted to females

# Autosomal Dominant disorders % of diseased, carriers, healthy

* 50% Diseased * 0% carriers * 50% healthy

# Autosomal dominant disorders carriers?

No carriers in AD

# Autosomal dominant disorders New mutations are not possible (T/F)

# Autosomal dominant disorders Examples of AD

* Hereditary spherocytosis * Marfan's * Achondroplasia * Ehlers- Danlos Xs * VwD * Tuberous sclerosis * Noonan Xd

# Autosomal dominant disorders When making pedigree charts the assumption we make

We assume one parent is normal, one parent is affected

# Autosomal dominant disorders Achondroplasia Sx

* Short stature- cannot touch their own shoulders by their hands * developmental delay

# Autosomal dominant disorders Ehlers- Danlos Syndrome

* Hypermobile joints * Stretchable skin * Aortic abnormalities

# Autosomal dominant disorders Tuberous sclerosis Sx

* Ash leaf macules * Shagreen patch- palpable * Adenoma sebaceum * Seizures

# Autosomal dominant disorders Marfan Syndrome Sx

* Tall, thin build * Flexible joints * Upward dislocation of lens * Occular HTN- glaucoma * Crowded teeth * High arched neck * Pectus excavatum, carinatum, scoliosis * Stretch marks * Disproportionately long arms, legs * Arachnodactyly * Flat feet

# Autosomal dominant disorders Cardiac abnormalities seen in Marfans

* Aortic aneurysm * Aortic dissection * Mitral valve prolapse

# Autosomal dominant disorders Nervous system, Respi system complocations seen in Marfans

* Nervous- dural ectasia * Respi- pneumothorax (bullae)

# Noonan Syndrome affects only males (T/F)

F- affects both male and female

# Noonan syndrome Sx

* disproportionately large head * High anterior hairline * **Triangle- shaped face** * Transparent, wrinkled skin * Prominent nasolabial folds * **Neck webbing** * wide- spaced eyes

# Noonan Syndrome Complications

* R/ heart problems- Pulmonary stenosis

L/ heart problems are seen in

Turner Syndrome

# Autosomal Recessive Disorders % of normal, carriers and affected

* 25% normal * 50% carriers * 25% affected

# Autosomal Recessive Disorders Assumption we make

We assume both parents are carriers

# Autosomal Recessive Disorders Common among

consanguineous marriages

# Autosomal Recessive Disorders To occur

child should have 2 abnormal chromosomes, one from each parent.

# Autosomal Recessive Disorders Some examples

* Congenital adrenal hyperplasia * Cystic fibrosis * Albinism * Phenylketonuria * Sickle cell disease

# Autosomal Recessive Disorders Cystic fibrosis Pathophysiology

* Thick airway secretions- recurrent infections * Secretions block the pancreas- lipase not produced * Lipids not digested properly- steatorrhea

# Autosomal Recessive Disorders Cystic fibrosis is seen

common in caucasians- not much seen in SL

# Autosomal Recessive Disorders Phenylketonuria pathophysiology

No PKU to convert phenylalanine to tyrosine. Toxic levels of Phenylalanine

# Autosomal Recessive Disorders Sx of PKU

* Mental retardation * Skin rashes * Behavioral problems * Convulsions * Musty body odor

# Autosomal Recessive Disorders Mx of PKU

* Avoid meat, dairy, dry beans. nuts, eggs * Give Phenylalanine free milk powder- very expensive

# Autosomal Recessive Disorders Sx of sickle cell disease

* Fatigue * jaundice * Breathless * body pains * swelling of arms, legs * arthralgia

# Autosomal Recessive Disorders Characteristic face seen in Sickle cell anemia

* Frontal bossing * malar prominence * crowded teeth

# X linked recessive disorders % of healthy, carriers and affected girls

* 50% carriers * 50% healthy * **NO AFFECTED**

# X linked recessive disorders % of healthy, affected and carrier boys

* 50% affected * 50% healthy * **NO CARRIERS**

# X linked recessive disorders Which genetic disorder can have a high risk of getting X linked recessive disorders

Turner Syndrome

# X linked recessive disorders Examples

* colour blindness * Duchenne muscular dystrophy * Fragile X syndrome * Hemophilia

# X linked recessive disorders Charts used to Dx colour blindness

Ishihara charts

# X linked recessive disorders Duchenne muscular dystrophy Dx

Muscle Biopsy

# X linked recessive disorders Duchenne Sx

* **Calf pseudohypertrophy** * thin weak thighs * weak buttock muscles * shoulders and arms held back awkwardly when walking * swayback posture

# X linked recessive disorders Duchenne characteristic sign

Gower's sign

# Duchenne Muscular dystrophy Gower's sign

Difficulty standing up in young boys. Get support from the legs and hunch to get support to stand up. Like old people

# X linked recessive disorders Fragile X syndrome Sx

* **Large prominent ears** * Broad forehead * Elongated face * Strabismus * high arched palate * hyperextensible joints * hand calluses * Pectus excavatum * Hypotonia * soft, fleshy skin * Enlarged testicles * flat feet

# Fragile X syndrome Cardiac abnormality

Mitral valve prolapse

# Fragile X syndrome Has Sx similar to Marfans (T/F)

True * High arched palate * Flat feet * hyperextensible joints * Pectus excavatum

# Fragile X syndrome Muscle tone

Hypotonia

# Fragile X syndrome Testicular volume atrophied (T/F)

False Enlarged testicles

Commonest cause for genetic mental retardation

Down Syndrome

2nd most common cause for mental retardation

Fragile X syndrome

# Fragile X syndrome Type of education

will need special schools.

# Hemophilia Sx

* Easy bruising * hemarthrosis * GI hemorrhage, ICH high risk

# Hemophilia Mx

* Factor VIII administration * Good dental hygiene * Good nutrition * Avoid injury and meals that promote bleeding