congenital/genetic disorders Flashcards
what is a congenital disorder
- “birth defect”
- result of developmental errors in embryo manifesting at birth
- present at birth, non-genetic
what is the period of vulnerability
a time in gestation when the embryo is most sensitive to developmental errors
organogenesis
period 15-60 days post-conception when organs begin to form
teratogen
any factor responsible for congenital abnormalities
ex. drugs, smoking, alcohol, malnutrition, infection
critical period for the CNS
2-5 weeks
critical period for the heart
2.5-5.5 weeks
critical period for the extremities
3.5-7 weeks
critical period for the eyes
3.5-7.5 weeks
critical period for the external genitalia
6.5-9 weeks
types of genetic abnormalities
- monogenic
- complex trait
- mitochondrial
- chromosomal
what is a monogenic abnormality
a single allele is affected; 3 types:
- autosomal dominant
- autosomal recessive
- x-linked recessive
autosomal dominant disorder
- monogenic abnormality
- only 1 defective allele needed for disease manifestation
- 50% probability
autosomal recessive disorder
- monogenic abnormality
- requires both defective alleles for disease manifestation
- 25% affected, 25% unaffected, 50% carriers
define autosomal
non-sex dominant chromosome
x-linked recessive disorder
- monogenic abnormality
- associated w/ female (X) chromosome
- males more often affected (XY)
- females rarely experience affects d/t having XX, one is still normal
- carrier mother = 50% sons affected, 50% daughter carriers
- affected father = sons unaffected, all daughters carriers
mitochondrial gene disorders
- maternal inheritance of mitochondrial genes (sperm lose mitochondria in tail)
- involved in ATP production
- code for enzymes involved in the respiratory chain (electron transport chain)
- cause neuromuscular defects d/t high requirement for oxidative metabolism (more ATP)
complex trait disorders
- polygenic and environmental factors
- is a predisposition
- not caused by predisposition alone, must be paired with environmental factors
define polygenic
caused by multiple genes
how many mitochondrial genes are there
37
how many chromosomes are there
46 (23 pairs)
chromosomal defects
defects in number or structure of chromosomes
what is a karyotype
a test to identify and evaluate the size, shape, and number of chromosomes in a sample
numeric chromosomal abnormality
- abnormal # chromosomes
- aneuploidy, trisomy, monosomy
- referred to by chromosome #
ex. trisomy 21 = down syndrome
aneuploidy
extra or missing chromosome
trisomy
extra chromosome in a pair (3 total)
monosomy
missing chromosome (1 total) will not occur w/ autosomal chromosome b/c absence of 50% of genetic material is not conducive to life
klinefelter’s syndrome
- trisomy, numeric problem
- male with additional X chromosome (XXY)
- 1 in 500
- manifestations: narrow shoulders, gynecomastia, wide hips, testicular atrophy, long arms/legs etc.
turner’s syndrome
- monosomy, numeric problem
- female with only 1 X chromosome (XO)
- 1 in 2500
- manifestations: broad chest, webbed neck, poor breast development, hormone deficiencies, infertility
structural chromosome abnormality
a section of the chromosome breaks off and does:
- inversion
- deletion
- translocation
chromosome inversion
piece of the chromosome is inverted
- pericentric: around the centrosome
- paracentric: away from the centrosome
chromosome translocation
piece of the chromosome transfers to another
- balanced: switch places
- Robertsonian: 1 long chromosome, 1 small that is lost
- isochromosomal: chromosomes split horizontally
chromosome deletion
- part of the chromosome is missing
- leads to a loss of genetic material
- ring formation: following deletion, forms ring
the word for extra or missing chromosomes
aneuploidy
the word for an extra chromosome in a pair (3)
trisomy
the word for missing a chromosome
monosomy
