GENETIC DISORDERS Flashcards
One dominant allele is enough to produce phenotype (heterozygous); diseases with mutations in key structural proteins/receptors are usually inherited in this manner;
Autosomal dominant
Two recessive alleles produce phenotype; enzyme deficiencies are usually inherited in this manner:
Autosomal recessive
In this pattern of inheritance, males are usually affected due to hemizygosity of the allele, but females may express phenotype due to random activation of one X chromosome;
X-linked recessive disorders
In this pattern of inheritance, females in general are more affected than males (in any scenario), because one allele in a female is enough to manifest the trait;
X-linked dominant disorders
Huntington disease,
Autosomal dominant
Cystic fibrosis
Autosomal recessive
Duchenne muscular dystrophy
X-linked recessive disorders
Alport syndrome
X-linked dominant disorders
Lesch-Nyhan syndrome
X-linked recessive disorders
Vitamin D-resistant rickets
X-linked dominant disorders
Hemophilia A and B
X-linked recessive disorders
Ehler-Danlos Syndrome (some types)
Autosomal dominant
Neurofibromatosis
Autosomal dominant
Myotonic dystrophy
Autosomal dominant
Phenylketonuria
Autosomal recessive
enzyme deficiencies are usually inherited in this manner:
Autosomal recessive
Chronic granulomatous disease
X-linked recessive disorders
Tuberous sclerosis complex
Autosomal dominant
Autosomal dominant
X-linked recessive disorders
Galactosemia, Homocystinuria, Lysosomal storage diseases, α-1-antitrypsin deficiency, Wilson disease, Hemochromatosis, Glycogen storage diseases, Sickle cell anemia, Thalassemias, Congenital adrenal hyperplasia, Ehler-Danlos Syndrome (some types), Alkaptonuria
Autosomal recessive
Neurogenic muscular atrophies, Freidrich ataxia, Spinal muscular atrophy
Autosomal recessive
Agammaglobulinemia, WiskottAldrich syndrome, Diabetes insipidus, Lesch-Nyhan syndrome, Fragile X syndrome
X-linked recessive disorders
Marfan syndrome
Autosomal dominant
ADPKD
Autosomal dominant
familial polyposis coli
Autosomal dominant
Osteogenesis imperfecta
Autosomal dominant
Marfan syndrome
Autosomal dominant
Achondroplasia
Autosomal dominant
Familial hypercholesterolemia, Acute intermittent porphyria
Autosomal dominant
Most common of the chromosomal disorders; leading cause of MR
Trisomy 21 (Down syndrome)
most common cause of trisomy 21
nondisjunction of Ch21 during meiosis
diagnostic clinical features: flat facial profile, oblique palpebral fissures, and epicanthal folds
Trisomy 21 (Down syndrome)
Prominent occiput, mental retardation, micrognathia, low-set ears, short neck, overlapping fingers, cardiac defects, renal malformations, limited hip abduction, and rocker-bottom feet are features of this syndrome
trisomy 18 (Edward syndrome)
Microcephaly and mental retardation, microphathalmia, cleft lip and palate, polydactyly, cardiac defects, umbilical hernias, renal defects, and rocker-bottom feet are features of this syndrome
Note: Italicized feature
trisomy 13 (Patau syndrome)
features that would differentiate Patau syndrome from Edward syndrome
cleft lip palate and umbilical hernias
Syndrome consisting of cardiac anomalies, abnormal facies, thymic hypoplasia, cleft palate, hypocalcemia,
DiGeorge syndrome
DiGeorge syndrome is due to
due to deletion in the long arm of Chromosome 22 (part of Ch22q11.2 deletion syndrome, together with velocardiofacial syndrome)
also known as 22q11.2 deletion syndrome
DiGeorge syndrome
is a genetic condition characterized by abnormal pharyngeal arch development that results in defective development of the parathyroid glands, thymus, and conotruncal region of the heart.
velocardiofacial syndrome
Condition characterized by ≥ 2 X chromosomes and ≥ 1 Y chromosomes
Klinefelter syndrome
most common karyotype is 47XXY
Klinefelter syndrome
Complete or partial monosomy of X chromosome; female hypogonadism in phenotypic females;
Turner syndrome
important cause of reduced spermatogenesis and male infertility;
Klinefelter syndrome
Most common abnormality is lack of entire X chromosome (45XO);
Turner syndrome
single most important cause of primary amenorrhea;
Turner syndrome
Type of hermaphrodism characterized by presence of both ovarian and testicular tissue
True hermaphrodism
Type of hermaphrodism characterized by disagreement between phenotypic and gonadal sex;
Pseudohermaphrod ism
syndromes with Pseudohermaphrodism
MRKH syndrome and androgenital syndromes
clinical features include: ovarian streaks, absence of secondary sex characteristics, short stature, cystic hygromas of head neck, preductal CoA, etc.
Turner syndrome
Most common cause of MR following Trisomy 21;
Fragile X syndrome
Fragile X-syndrome
most distinctive feature is
macroorchidism
Fragile X-syndrome
due to
CGG expansion in FMR1 gene in X-chromosome;
Autosomal dominant neurodegenerative disorder;
Huntington disease
Huntington disease
due to
CAG expansion on HTT gene on Ch4
CAG expansion on HTT gene on Ch4; relentlessly progressive and uniformly fatal
huntington disease
Deletion in paternally derived Chromosome 15;
Prader-Willi syndrome
clinical features include: mental retardation, hypotonia, profound hyperphagia, obesity, small hands and feet, and hypogonadism
Prader-Willi syndrome
Deletion in maternally derived Chromosome 15;
Angelman syndrome
clinical features include: mental retardation, ataxic gait, seizure, and inappropriate laughter “happy puppet”
Angelman syndrome
