Patho - Genetic and Congenital Disorders Flashcards
what are genetic disorders?
-caused by single genes usually follow autosomal dominant, autosomal recessive, or x-linked recessive models of inheritance
-apparent at birth
-majority inherited from parents; some d/t fetal development mutations
what are chromosomal aberrations?
Abnormality in structure/number of chromosomes. Leading cause of mental retardation & miscarriage Incidence of chromosomal abnormalities
-1/12 conceptions
-Approx. 95% of conceptions result in miscarriage
-50% of 1st trimester miscarriages associated with major chromosomal abnormality
-1/150 live births with major diagnosable chromosomal abnormality
Causes Risk factors: poorly understood
1. advanced maternal age
2. abnormalities in prenatal genetic structure
3. abnormalities in meiosis
what is trisomy 21 (down syndrome)?
-extra copy of 21st chromosome
-most common chromosomal disorder
-leading cause of intellectual disability
-protruding tongue, low-set ears, epicanthal folds, poor muscle tone, short stature; congenital heart deformities, increased susceptibility to respiratory infections, leukemia, memory loss
-associated with advanced maternal age
what is klinefelter syndrome?
-most common genetic disease of sex chromosomes
-affects males, usually 1 extra X chromosome (xxy genotype)
-lack of secondary sex characteristics during puberty
what symptoms are associated with klinefelter syndrome?
-lack of testosterone
-testicular atrophy; infertility
-feminine hair distribution/gynecomastia (enlargement of breast tissue)
-tall stature, long arms/legs
-high-pitched voice
-impaired intelligence
what is turner syndrome (monosomy X)?
-1 normal X chromosome; no Y chromosome
-1:3000 births
-female phenotype with no functioning ovaries
-2nd X chromosome missing or structurally abnormal; usually d/t father’s advanced age
-short stature, webbed neck, fibrous ovaries, sterility, amenorrhea, wide chest, congenital heart defects
-no mental retardation - live fairly normal lives
what is mendelian single-gene disorder?
-Alterations or mutations of single genes
-Pedigree may help trace transmission through the family
-Classified according to location of defective gene and mode of transmission
1. autosomal dominant
2. autosomal recessive
3. sex-linked (X-linked)
what is marfan syndrome?
-Connective tissue disorder
-Tall, slender; long, thin arms/legs & fingers
-Cardiovascular lesions most threatening
-Aorta usually weak, susceptible to dilation/rupture
what are the three autosomal recessive disorders? what are they?
Albinism: lack of pigmentation from disrupted melanin synthesis
Phenylketonuria: Inborn error of metabolism -cannot metabolize phenylketonuria - test at birth
Cystic fibrosis: most common –
thick secretions d/t lack of chloride transport across
what are sex-linked (X-linked) disorders?
-Inherited mutation of sex chromosome (almost always X)
-Nearly all X-linked disorders are recessive
-males always express disease and females rarely affected (since males are XY)
what is non mendelian single-gene disorder?
-caused by long triplet repeat mutations, ie; fragile X syndrome
-d/t mitochondrial DNA mutations
-associated with genomic imprinting
what is fragile X syndrome?
-premutation: possible to have intermediate number of inherited repeats which increase the risk of mutation
-males more severely affected
what are multifactorial (polygenic) disorders?
-interaction of multiple gene
-very common
-“run in families”
-also present range of severity
-difficult to predict based on family history
-multifactorial disorders– high blood pressure, cancer, diabetes
-multifactorial traits– height, weight, intelligence
what are environmentally induced congenital disorders?
-errors in fetal development that result in congenital malformations
-numerous environmental influences (teratogens) may adversely affect developing fetus
teratogenic agents:
-chemical and drugs (alcohol)
-infectious agents (viruses, rubella)
-radiation
-susceptibility depends on amount of exposure, developmental age, and teratogen
-may produce death, retardation, malformation, or functional impairment
what are the periods of fetal vulnerability in environmentally induced congenital disorders?
-before 3rd gestational week: teratogen exposure either damages very few cells or so many that embryo cannot survive
-3rd to 9th week: embryo very susceptible to teratogenesis (especially 4th and 5th weeks during organ development)
-after 3rd month, teratogens affect growth or injury to already formed organs
