Simple and complex genetic diseases
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Simple and Complex Genetic Diseases. Simple: One gene -> one disease Example: sickle-cell anemia Complex: Many genes interacting with other and the environment -> one disease Examples: MS, Types I, II diabetes. Single Gene Disorders. Autosomal recessive Albinism Cystic fibrosis

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Simple and Complex Genetic Diseases

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Simple and complex genetic diseases

Simple and Complex Genetic Diseases

  • Simple: One gene -> one disease

  • Example: sickle-cell anemia

  • Complex: Many genes interacting with

  • other and the environment -> one disease

  • Examples: MS, Types I, II diabetes

Single gene disorders

Single Gene Disorders

Autosomal recessive

  • Albinism

  • Cystic fibrosis

  • Phenylketonurea



Metabolic disorder defect in galactose meatbolism,

  • The problem in the enzyme galactose 1- phoshate uridyl transferese, Which breakdown glucose.

  • This leads to accumulation of galactose in blood, leads to blood poisoning which cause:

  • 1- Hepatomegaly

  • 2- Cirrrhosis

  • 3- Renal failure

  • 4- Cataracts

  • 5- Brain damage



  • Absence of lysosomal enzymes (α-L-iduronidase) which digest Mucopolysaccharide (also named


  • This sugar is found in the liquid between joints and act as lubricant.

Autosomal dominant

Autosomal dominant


  • Askeletal disorder causeing dwarfism, shortening in limbs and digits, enlargement in skull.

  • Caused as a defect in Fibroblast Growth factor Receptor Gene3 (FGFR3)

  • This leads to a defect in cartilage and bone growth.

Marfan syndrome

Marfan syndrome

  • 15q 15-21

  • Affect c.t

  • Defect in FBN1 gene



  • 17q11

  • Swallow sacs under skin affect skin, bone and nerves

  • Caused as a defect in the Neurofibromin gene.



5p13 and 2q33

  • Problem in fingers

    Noonan syndrome

  • Defect in PTPN11 gene which encode

  • Protain Tyrosine Phosphatase, which play a role in embryonic development, Differentiation and migration

Huntington s disease

Huntington's disease

  • 4p16

  • Trinucleotide repeat expansion in the gene which encode Huntington protein.

  • This leads to defect in the produced protein, degeneration in neurons, and chorea.

1 glucose 6 ph dehydrogenase deficiency

1 Glucose-6-ph. Dehydrogenase deficiency

  • X-Linked r

  • Deficiency in

  • Glucose-6-ph. dehydrogenase enzyme

    ( G6PDH)

  • This enzyme is related to Pentose phosphorylation Pathway

  • This enzyme converts Glucose-6-ph to 6- Phosphogluconate delta-lactone

Duchenne muscular dystrophy

Duchenne muscular dystrophy

  • Defect in the gene which encode Dystrophin

    Haemophilia A

  • Defect in the gene which encode Factor VIII



  • X-linked dominant disorders

  • a form of vitamin D- resistant rickets

Y linked genes

Y-linked genes

  • Sex determining gene (SRY) encodes SDF which important in sex determination by playing a role in early stages of testis differentiation.

  • Any defect cause XY female (Swyer syndrome)

  • Translocation of part Y chromosome which contain SRY gene to X chromosome give XX male syndrome

Simple and complex genetic diseases

  • ANT3 (adenine nucleotide translocase)

  • Produce enzyme change and transfer ADP from internal mitochondria to ouside as ATP



  • Colony stimulating factor 2 receptor α

  • Produce cell surface receptor for growth factor

  • Control production, differentiation of granulocytes and macrophages.

H y gene

H-Y gene

  • Plasma membrane protein

  • Play a role in testis differentiation

Simple and complex genetic diseases


  • Zinc finger protein

  • DNA binding protein that regulate gene expression

Mitochondrial disorders

Mitochondrial disorders

  • Mitochondrial myopathy

  • neurodegenerative disorder

  • seizures, diabetes mellitus, hearing loss, short stature, and exercise intolerance are clearly part of the disorder.

Merrf syndrome

MERRF syndrome

  • muscular disorders

  • cause a dysfunction of the brain and muscles (encephalomyopathies).

Simple and complex genetic diseases

  • The most characteristic symptom of MERRF syndrome is seizures that are usually sudden, brief, jerking, spasms that can affect the limbs or the entire body.

  • Impairment of the ability to coordinate movements (ataxia), as well as an abnormal accumulation of lactic acid in the blood (lactic acidosis) may also be present in affected individuals.

  • Difficulty speaking (dysarthria), optic atrophy, short stature, hearing loss, and involuntary jerking of the eyes (nystagmus)

Leigh syndrome

Leigh syndrome

  • progressive neurodegenerative disorder in one or more areas of the central nervous system, including the brainstem, thalamus, basal ganglia, cerebellum, and spinal cord.

  • The lesions are areas of demyelination, gliosis, necrosis, spongiosis, or capillary proliferation. Clinical symptoms depend on which areas of the central nervous system are involved.

  • The most common underlying cause is a defect in oxidative phosphorylation

Sideroblastic anemia

Sideroblastic anemia

  • abnormal production of RBCs which can evolve into leukemia.

  • Thus, the body has iron available, but cannot incorporate it into hemoglobin

  • The common feature of these causes is a failure to completely form heme- whose biosynthesis takes place partly in the mitochondria. This leads to deposits of iron in the mitochondria that form a ring around the nucleus of the developing RBCs. This leads to a stage in bone marrow disorder that leads to acute leukemia.



  • involuntary twitching of muscles.

  • The myoclonic twitches or jerks are usually caused by sudden muscle contractions; Contractions are called positive myoclonus; relaxations are called negative myoclonus.

  • myoclonic jerks are also a sign of a number of neurological disorders.

  • Hiccups are also a kind of myoclonic jerk specifically affecting the diaphragum.

Simple and complex genetic diseases

  • myoclonus is one of several signs in a wide variety of nervous system disorders such as Parkinson’s disease, Alzheimer’s disease, and some forms of epilepsy



  • affect muscles connected to bones (called skeletal muscles), such as the biceps in the upper arm and the quadriceps in the thigh.

  • Myopathies can be caused by inherited genetic defects (e.g., muscular dystrophies), and endocrine, inflammatory , and metabolic disorders.



  • the heart muscle becomes inflamed and doesn't work as well as it should.

  • There may be multiple causes including viral infections.

  • Cardiomyopathy can be classified as primary or secondary.

  • Primary cardiomyopathy can't be attributed to a specific cause, such as high blood pressure, heart valve disease, artery diseases or congenital heart defects.

  • Secondary cardiomyopathy is due to specific causes. It's often associated with diseases involving other organs as well as the heart.

Renal tubular acidosis rta

Renal tubular acidosis (RTA)

  • is a disease that occurs when the kidneys fail to excrete acids into the urine, which causes a person's blood to remain too acidic.

  • Without proper treatment, chronic acidity of the blood leads to growth retardation, kidney stones, bone disease, and progressive renal failure.

  • The word acidosis refers to the tendency for RTA to lower the blood's pH. When the blood pH is below normal (7.35), this is called acidemia.

  • Its causes are diverse, and its consequences can be serious, including coma and death.

Variation in chromosome number

Variation in chromosome number

  • Trisomy 18 (47,XY,+18) – Edward

  • Syndrome

Simple and complex genetic diseases

Trisomy 18• Incidence 1:3333 live births• Most common abnormality in stillbirths with multiple congenital abnormalities• Prenatal growth deficiency resulting in a small for gestational age infant (SGA)•90% congenital heart defect VSD• 10% alive at one year• Marked developmental disability

Trisomy 18 physical features

Trisomy 18 -Physical Features

  • • Prominent occiput

  • • Micrognathia

  • • Microcephaly

  • • Low set malformed ears

  • • Characteristic clenched fists

  • • Rocker-bottom feet

  • • Short big toe that is dorsiflexed

Simple and complex genetic diseases

  • Trisomy 18 –Edward Syndrome

  • Trisomy 18

  • • Prominent Occiput

  • • Low-set malformed ears

  • • Small chin

  • • Clenched fists

Simple and complex genetic diseases

  • Trisomy 18

  • • Ocular manifestations in 10%

  • • Low-arch dermal ridge pattern

  • • Underdeveloped nails

  • • Congenital anomalies of lungs,diaphragm, and

  • kidneys

  • • Hernias, cryptorchidism, rectus muscle separation

Simple and complex genetic diseases

  • Trisomy 13 (47,XY,+13) – Patau

  • Syndrome

Simple and complex genetic diseases

  • Trisomy 13

  • • Incidence 1:5,000 births

  • • Distinctive malformation pattern

  • (Craniofacial and Central Nervous System)

  • • 95% spontaneously aborted

  • • Survival rate and development similar to Trisomy 18

Simple and complex genetic diseases

  • Trisomy 13 PatauSyndrome

  • • Microcephalywith sloping forehead

  • • Holoprosencephaly

  • • Ophthalmologic abnormalities microphthalmiaor anophthalmia Colobomataof iris and ciliarybody

  • • Cleft lip +/-palate

  • • Low set ears with abnormal helices

Simple and complex genetic diseases

  • Trisomy 13 PatauSyndrome

  • • Cardiac defects: ASD, PDA, VSD

  • • Males: cryptorchidism ; Females: Bicornuateuterus

  • • Polycystic kidneys

  • • Aplasiacutis congenita

  • • Polydactylyof hands +/-feet

  • • Rockerbottomfeet

Turner syndrome

Turner syndrome






Xxx females

XXX females

  • About one woman in 1000 has an extra X chromosome. It

  • seems to do little harm, individuals are fertile and do not

  • transmit the extra chromosome.

Xyy males

XYY males

  • XYY males Incidence 1 in 1000 male births.

  • May be without any symptoms. Males are tall but normally proportioned.

Simple and complex genetic diseases

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