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Genetics > Disorders > Flashcards

Disorders Flashcards

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1
Q

Myotonic Dystrophy

A

Wasting of the muscles, cataracts, heart conduction defects, endocrine changes, and myotonia.

  • Mutation in DMPK gene. DM1 most common
  • Triplet Repeat Disorder (CTG repeat) at 3’ end of gene

-Autosomal Dominant

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2
Q

Achondroplasia

A

FGFR3 (Arg360Gly) mutation results in severe stunting of growth

Codes for transmembrane receptor involved in differentiation of cartilage to bone.

-Autosomal Dominant

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3
Q

Neurofibromatosis

A

Mutations in neurofibromin(NF1) gene.

Neurofibromin gene codes for a tumor suppressor protein

  • Café-au-lait spots
  • Neurofibromas: swellings on the skin
  • Lisch nodules in the iris of the eye
  • Exhibits variable expressivity
  • Autosomal Dominant
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4
Q

Hemochromatosis

A

Excess Iron. Deposits in organs, especially liver, heart and pancreas leading cancer, heart arrhythmias, cirrhosis, etc.

  • C282Y mutation of HFE gene most common
  • delayed age of onset

-Autosomal Recessive

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5
Q

X-linked recessive disorders

A

Dystrophin gene: DMD, Becker MD
G6PD deficiency
Hemophilia A & B
Lech-Nyan Syndrome: HGPRT deficiency

X-linked SCID: defect in SCIDX1 gene
(defect in the gamma chain of the receptor for several different interleukins)

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6
Q

Rett Syndrome

A

Neurodevelopmental, autism spectrum disorder characterized by developmental reversals, especially in the areas of expressive language and hand use.

  • X-linked dominant.
  • Males with mutant X usually die in utero

Mutation in MeCP2 (methylation/epigenetics)

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7
Q

Incontinentia pigmenti

A

X-linked dominant

–Males with the disorder die in utero
–Manifests as rashes & blisters in early life
–Later, patches of hyperpigmentation, ‘Marble cake appearance’ of skin
–Mental retardation (in some patients)
–Retinal detachment (in some patients)

Variable expressivity

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8
Q

Huntington Disease

A

Neurodegenerative disorder, affects muscle coordination leading to cognitive decline and psychiatric problems.

  • Triplet repeat expansion (CAG) in coding region of DNA (36-100 repeats)
  • Genetic anticipation
  • Autosomal Dominant
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9
Q

Familial hypercholesterolemia

A

High LDL due to LDL receptor deficiency

-Autosomal Dominant

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10
Q

Marfan Syndrome

A

Connective tissue disorder due to misfolding of fibrillin.

-Autosomal dominant

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11
Q

Osteogenesis imperfecta

A

‘Brittle bone disease’
Defective connective tissue, deficiency of Type-I collagen.

-COL1A1 and/or COL1A2 gene mutations

  • Haploinsufficiency (loss of function of 1 allele)
  • Autosomal Dominant
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12
Q

Acute intermittent porphyria

A

Deficiency of porphobilinogen deaminase in the formation of heme. build up of porphobilinogen and amino-levulinic acid (ALA)

neurologic damage that leads to peripheral and autonomic neuropathies and psychiatric manifestations, and abdomen pain

-Autosomal dominant

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13
Q

Cystic Fibrosis

A

-Autosomal Recessive

Abnormal transport of chloride and sodium across an epithelium, due to CFTR receptor abnormality

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14
Q

Sickle Cell Anemia

A
  • Autosomal Recessive
  • codominance can occure

Characterized by red blood cells that assume an abnormal, rigid, sickle shape. mutation in hemoglobin gene.

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15
Q

Phenylketonuria (PKU)

A

-Autosomal Recessive

Deficient Phenylalanine hydroxylase or the BH4 coenzyme. Inability to break down phanyalanine to tyrosine.

Intellectual disability. Seizures, delayed development, behavioral problems, and psychiatric disorders.

Mousy odor to urine

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16
Q

Tay-Sach’s disease

A

-Autosomal Recessive

Hexosaminidase A deficiency. buld up of ganglioside in nerve cells of the brain resulting in premature death. .

cherry-red spot on retina and onion appearance to lysosomes.

17
Q

Congenital deafness

A
  • Autosomal recessive

- Locus heterogeneity

18
Q

Homocystinuria

A

-Autosomal recessive

Cystathionine beta synthase deficiency in the breakdown of methionine resulting in accumulation of homocystine.

Intellectual disability, failure to thrive, seizures, problems with movement, megaloblastic anemia.

-Delayed age of onset

19
Q

Galactosemia

A

-Autosomal Recessive

Inability to break down galactose resulting in failure to thrive, seizures, lethargy, liver damage, etc.

20
Q

Severe Combined Immunodeficiency

A
  • Autosomal Recesive - adenosine deaminase deficiency in purine degradation build up of dATP toxic to B & T cells
  • X-linked recessive - SCIDX1 gene mutation leading to mutation in the gamma chain of T cell receptors

Absence of functional T-lymphocytes

Treatment:
Bone marrow transplant
Protein therapy
Gene therapy

21
Q

Lech-Nyan Syndrome

A
  • X-linked recessive

HGPRT deficiency resulting in neurological manifestations,hyperuricemia, gout, and self mutilation.

22
Q

Duchenne muscular dystrophy

A
  • X-linked recessive

mutation on the dystrophin gene resulting in muscle wasting and cardiac problems Death before 30.

Becker’s MD a milder form.

23
Q

Glucose 6 phosphate dehydrogenase(G6PD) deficiency

A
  • X-linked recessive

Hemolytic anemia on ingestion of primaquine, sulfa drugs

24
Q

Hemophilia A and B

A
  • X-linked recessive

Bleeding disorder resulting in deficient Factor VIII

25
Q

Red/Green Color Blindness

A
  • X-linked recessive
26
Q

Mitochondria disorders

A

MERRF
MELAS
Leber hereditary optic neuropathy

Varying degree of disorder due to heteroplasmy

All children of an affected mother will be affected.

27
Q

Fragile X Syndrome

A
  • X-Linked dominant, w/ reduced penatrance, anticipation, and x-inactivation

Triple repeat disorder (CGG repeat) at promotor region

increased methylation of FMR1

Mental retardation, learning difficulties, prominent ears, elongated face, macro orchidism(enlarged testis)

Females less affected.

Cytogenetic test: When cells are cultured in a folate deficient medium the X chromosomes reveals a ‘fragile’ site

28
Q

Retinitis Pigmentosa

A

Digenic Disorder (need AaBb for disease)

–a disease of progressive visual impairment
–a result of a mutation in two independent genetic loci (ROM1 and peripherin)

29
Q

Prader Willi Syndrome

A

-Imprinting Disorder
Microdeletion of Paternal 15q11-13 (absence of SNRPN)
or
Uniparental disomy, two copies of the maternal chromosome 15

Obese, Mental and developmental delay, underdeveloped genitalia, Hypotonia in infancy, failure to thrive

30
Q

Angelman syndrome

A

-Imprinting disorder
Deletion of maternal15q11-13 (absence of active UBE3A gene)/ Uniparental disomy of paternal chromosome 15

Severe mental retardation, seizures Puppet like posture of limbs

31
Q

Xeroderma Pigmentosa

A

Autosomal Recessive
Locus Heterogeneity

Mutation is Nucleotide Excision Repair (NER) genes

-clinical sun sensitivity, sunburn, blistering, freckledwith hyper-pigmented skin lesions

Increased risk of skin cancer >1000 fold. DNA damage is cumulative

32
Q

Hereditary Nonpolyposis Colon Cancer

A

A result in mutations in mismatch repair genes causing microsatillite instability.

33
Q

Bloom Syndrome

A

Defect in BLM gene that codes a DNA helicase used in replication and recombination repair. Causes chromosomal instability and breakage.

Characteristics:

  • smaller than average
  • narrow chin, prominent nose and ears
  • facial rash (pigment and dilated blood
    vessels) upon exposure to sun
  • often get diabetes and have neurological,lung and immune system deficiencies, higher incidence of certain cancers.
34
Q

Ataxia Telangiectasia

A

Autosomal Recessive

Defect is in ATM = A serine/threonine kinase for detecting DNA damage and activating cell cycle arrest and
DNA repair proteins (e.g. p53)

Affects the cerebellum (ataxia), increased cancer rates, occular telangiectasia

35
Q

Alpha Thalassemia

A

Hemolytic disorder. Deficiency of Alpha globin cain synthesis.

(aa/a_) Silent Carrier
(aa/_ ) Alpha Trait, Mild enemia - normal or slightly low Hb
(a/_ _) HbH Syndrome, Moderate anemia w/hepatoslenomegaly and bone malformations- Formation of beta tetramers

36
Q

Hydrops Fetalis

A

aka - Hb Bart Syndrome

Absence of all 4 Alpha globin genes (_ / _), aggregation of gamma tetramers.

Fetal onset of generalized edema, ascites, pleural and pericardial effusions, and severe hypochromic anemia

Neonatal fatality.

37
Q

Beta Thalassemia

A

Autosomal Recessive
Allelic Heterogeneity

Mutation of HBB gene on chromosome 11

Beta+ = reduced gene expression
Beta 0 = complete suppression of gene expression

Absence of beta chains result in formation of Alpha tetramers the precipitate resulting in hemolytic anemia

3 beta thalassemia types:
Major (Cooley’s Syndrome) - Homozygous or compound hetero. B+ or B0

Intermedia - Homozygous or compound Hetero for 2 different B+

Minor - Heterozygous, carrier, almost normal Hb

38
Q

Friedrich’s Ataxia

A

Mutation in Frataxin gene of an intron
Triple repeat expansion GAA
Recessive

Muscle weakness, vision and coordination problems, diab., heart disease.

39
Q

Spinocerebellar Ataxia

A

Triple repeat disorder
Locus Heterogeneity

Can present as dominant, recessive, or x-linked

Muscle degenerative disorder

Genetics (9 decks)

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