Genetic Disorders Flashcards by Erwin Corinales

Structural or numerical alteration in autosome and sex chromosome

Chromosomal disorder

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Interaction between multiple variant forms of genes and environmental factors

Complex multigenic disorders

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Permanent change in the DNA that can be transmitted to progeny

Germ cell mutation

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Permanent change in the DNA that does not cause hereditary diseases but are important in carcinogenesis

Somatic cell mutation

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Change in single nucleotide base within a gene

Point mutation

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Point mutation altered DNA codes for the same amino acid

Silent mutation

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Point mutation altered DNA codes for a different amino acid

Missense mutation

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Point mutation altered DNA codes for a stop codon

Nonsense mutation

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Stop codons

UAA
UGA
UAG

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Start codon

AUG

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Occurs if the number of base pairs involved is not a multiple of three

Frameshift mutation

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Transmitted only through mother where all offspring of affected females show signs of disease

Mitochondrial inheritance

Mitochondrial myopathy, encphalomypathy, lactic acidosis, stroke-like symptoms
Leber’s hereditary optic neuropathy

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Autosomal dominant, tall with long extremities, lax joint ligaments (hyperextensible thumb) doliocephalic frontal bossing, ectopia lentis, aortic dissection

Marfan syndrome

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Defective extracellular glycoprotien in Marfan’s Syndrome

Fibrillin-1

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Ocular change in marfan syndrome

Ectopia lentis

Bilateral subluxation or dislocation of the lens (out and up)

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In Marfan syndrome, CYSTIC MEDIAL NECROSIS of the ascending aorta will predispose them to

Aortic dissection (cause of death 30-45%)

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Result in defective synthesis of structure of fibrillar collagen. Skin is extraordinarily stretchable, extremely fragile, and vulnerable to trauma

Ehlers-danlos syndromes

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Differentiates marfan syndrome from EDS

Ectopia lentis
MVP
Aortic dissection

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Mutation in gene encoding for LDL receptor, loss ofmfeedback control and elevated levels of cholesterol. (Premature atherosclerosis and increased risk for MI)

Familial hypercholesterolemia

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Deficient in Tay-Sach’s disease

Hexosaminidase a-subunit

Associated with relentless motor and mental deterioration

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Lysosomal accumulation of sphingomyelin d/t deficient sphingomyelinase

Niemann-Pick disease

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Type of Niemann-pick disease that is severe infantile form with extensive neurologic involvement and organomegaly

Type A

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Niemann-pick disease type with organomegaly and NO CNS involvment

Type B

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Common finding of Tay-sachs disease and Niemann-pick disease

Cherry red spot in macula

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Differentiates Niemann-pick from Tay-sach's

Presence of Organomegaly

Most common lysosomal storage disorder

Gaucher disease

Cluster of autosomal recessive disorders resulting from mutations in the gene encoding glucocerebrosidase

Gaucher disease

Deficient in Gaucher disease

Glucocerebrosidase

Distended phagocytic cells with crumpled tissue paper appearance

Gaucher cells

Gaucher cells common location

Near arterioles (Virchow Robin spaces)

Race with exceptionally high prevalence of genetic disease

Ashkenazi jews

The only autosomal recessive MPS (mucopolysaccharidoses)

Hunter syndrome (X-linked recessive)

Common histologic finding in Niemann-pick and Mucopolysaccharidoses

Zebra bodies

Present in mucopolysaccharidoses. Distended cells with apparent clearing of the cytoplasm

Balloon cells

First human inborn error of metabolism

Alkaptonuria

Blue-black pigmentation evident in ears, nose and cheeks in patients with Alkaptonuria

Ochronosis

Autosomal recessive disorder that lacks HOMOGENTISTIC OXIDASE

Alkaptonuria

Unequal separation of chromosomes in meiosis 1

Nondisjunction

Mitotic errors in early development that give rise to two or more populations of cells with different chromosomal complement

Mosaicism (eg. Turner's syndrome, Down syndrome)

Loss of portion of a chromosome (eg. Cri du Chat syndrome)

Deletion

Transfer of chromosome parts between nonhomologous chromosomes

Translocation

Type of translocation without loss of genetic material

Balanced translocation

Type of translocation where transfer of segments leads to one very large chromosome and one extremely small one.

Robertsonian translocation

Most common chromosomal disorder

Down syndrome (95% of cases, trisomy 21)

Risk factors for Down Syndrome

Increasing maternal age (women >45yo)

Most common genetic cause of mental retardation

Down syndrome

Leukemia in down syndrome

>3yo ALL

Expected result in QUADRUPLE SCREEN for down syndrome

Increased b-HCG and inhibin A | Decreased AFP and Estriol

Expected ultrasonographic finding in patients with Down Syndrome

Increased nuchal transparency

Trisomy 18

Edwards syndrome

Rocker bottom feet, MR, VSD, micrognathia, clenched hands

Edwards syndrome (Trisomy 18)

Trisomy 13

Patau Syndrome

VSD, rocker bottom feet, polydactyly, holoprosencephaly, cleft lip and palate

Patau Syndrome (trisomy 13)

Clinical manifestation of Di George Syndrome

``` Cardiac defects Abnormal facies Thymic aplasia Cleft palate Hypocalcemia 22q11.2 deletion ```

Derivative of 1st branchial pouch

Middle ear cavity Eustachian tube Mastoid air cells

Derivatives of 2nd branchial pouch

Epithelial lining of palatine tonsils

Derivatives of 3rd branchial pouch

Thymus | L & R inferior Parathyroid

Derivatives of 4th branchial pouch

L & R superior parathyroids

``` Prominent nose Retrognathia Cleft palate Cardiovascular abnormalities Learning disability ```

Velocardiofacial syndrome

Klinefelter Syndrome

47XXY Male hypogonadism Testicular atrophy Eunochoid body shape

Turner syndrome

XO, no barr body | Short stature

Location of aortic coarcation in Turner syndrom

Preductal

Most common cause of primary amenorrhea

Ovarian dysgenesis

Microdeletion of long arm of chromosome 7

Williams syndrome

``` Elfin facies Extreme friendliness Well developed verbal skills Hypercalcemia MR ```

Williams syndrome

Ambiguous genitalia

True hermaphrodite

Usual karyotyoe of true hermaphroditism

46,XXY

2nd most common genetic cause of mental retardation

Fragile X syndrome

Prototype trinucleotide diseae

Fragile-X syndrome

Large mandible, large everted ears, macro orchidism

Fragile-X Syndrome

Microdeletion, paternal chromosome 15

Prader-Willi Syndrome

Microdeletion, maternal chromosome 15

Angelman syndrome

``` Wide based gait (marionette) Inappropriate laughter (happy puppet syndrome) ```

Angelman syndrome

Mutations in single gene with large effects (High penetrance)

Mendelian disorders

Genetic Disorders Flashcards

(74 cards)