Genetics Flashcards
3 primary types of mutations
- genome mutation
- chromosomal mutations
- gene variant
genome mutation
loss or gain of an entire chromosome
chromosomal mutation
alteration of a segment of chromosome
gene variant
partial or complete deletion of a gene
chromosomes
long chain DNA
genes
segment of DNA
human typical chromosomes and pairs
- 46 chromosomes
- 23 pairs
- 22 pairs of autosomal chromosomes
- 1 pair of sex chromosomes
hereditary or familial
condition derived from parents due to a genetic mutation
congenital
condition present at birth
- may be hereditary or derived from action or exposure during pregnancy or birth
not all hereditary conditions are congenital? true or false
true
not all congenital conditions are hereditary? true or false
true
types of inheritance patterns
- autosomal dominant
- autosomal recessive
- x-linked recessive
- chromosomal
- genetic conditions with mixed inheritance patterns
autosomal dominant
the gene in question is located on one of the 44 numbered, or non-sex chromosomes
autosomal dominant
a single copy of the mutated gene is enough to cause phenotypic expression
autosomal dominant mutation
low density lipoprotein (LDL)
- receptor mutation that results in impaired uptake of cholesterol into cells
autosomal dominant clinical manifestations
- elevated blood cholesterol levels
- atherosclerosis resulting in cardiovascular disease
-death before the age of 30 due to uncontrolled CVD
autosomal dominant: marfan syndrome
- mutation: 1 geen on chromosome 15q21
-fibrillin provides support for production of elastic fibers
clinical manifestation: marfan syndrome
- skeletal: long arms, legs, and fingers
- eye: bilateral dislocation of the lens
- cardiovascular: aortic root dilation leading to aortic insufficiency
osteogenesis imperfecta
- autosomal dominant ~ 80%
- autosomal recessive ~ 20%
- heterogeneous
- pleiotropic
pleiotropic
one gene influence 2 phenotypic traits
90% of osteogensis imperfects cases are caused by?
the mutation of the COL1A1 or COL1A2 genes
- both of these genes encode type 1 collagen
osteogenesis imperfecta type 1
mild:
- short stature
- postnatal fractures
- little or no deformity
- blue scleras (blue in the whites of eye)
- premature hearing loss
osteogenesis imperfecta type 2
perinatal lethal: LIFE THREATENING
- severe prenatal fractures
- abnormal bone formation
- severe deformities
- blue scleras
- connective tissue fragility
~ most severe
osteogenesis imperfecta type 3
progressive deforming:
- prenatal fractures
- deformities usually present at birth
- very short stature
- usually nonambulatory
- blue scleras
- hearing loss
osteogenesis imperfecta type 4
deforming with normal scleras:
- postnatal fractures
- mild to moderate deformities
- premature hearing loss
- normal or gray scleras
- dental abnormalities imperfect
osteogenesis imperfecta
- brittle bones
~ significant phenotypic heterogeneity subtypes and within subtypes - often present in early childhood with one or more fractures due to minimal trauma
- x-rays show mild osteopenia
osteogenesis imperfecta pathophysiology
disease of the type 1 collagen: major extraceullular protein in the body
ex.
- dermis
- connective tissue of the organs, GI, and vascular system
- bones
severity of osteogenesis imperfecta
type 1 < type 4 < type 3 < type 2
autosomal recessive
the gene in question is located on one of the 44 numbered, or non-sex chromosomes
- a single copy of the mutated gene is carrier but not expressed; two copies of the mutated gene are required for phenotypic expression
autosomal recessive: cystic fibrosis
mutation: cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7
- epidemiology: 1 in 3500 live births; white predominantly
clinical manifestations of cystic fibrosis
- fibrosis of pancreas
- recurrent pulmonary infections (pneumonia)
- chronic bronchitis (bronchiectasis)
- meconium ileus
- biliary cirrhosis, leading to impaired absorption of fat-soluble vitamins A,D,E, and K
- infertility in males secondary to absence of vas deferens
- thick and sticky mucus secondary to absence of chloride on cell surface
why is there increased concentration of chloride in sweat in cystic fibrosis patients?
due to inability of chloride to move in and out of cells
x-linked recessive
refers to genetic conditions associated with mutation in genes on an X chromosome
ex. duchenne muscular dystrophy
x linked recessive: duchenne muscular dystrophy
- mutations: dystrophin gene at Xp21
- epidemiology: 1 in 3000 infants; profound in male and female carriers are typically asymptomatic
clinical course of muscular dystrophy
- disease manifests by the age of 5 years
- associated muscular weakness leads to immobility by the early teens
- usually death by the 20s or 30s
- cardiomyopathy and non-progressive cognitive abnormalities are common
clinical manifestations signs and symptoms: muscular dystrophy
- weakness of pelvis first -> delayed ability to walk
- pseudohypertrophy -> enlargement of calf muscles due to replacement with fat
- gower maneuver -> use of hands to rise to a standing position
- muscle atrophy and weakness progress relentlessly -> wheelchair dependant by the second decade
- in most cases death due tp respiratory insufficiency and cardiac failure
chromosomal inheritance pattern
mutation of a large segment or entire chromosome
ex.
- down syndrome
- trisomy 18
down syndrome
- extra copy of chromosome 21 in each cell (trisomy 21)
clinical manifestations:
- intellectual disability
- characteristic facial features
- hypotonia
- protruding tongue
- congenitial heart disease
epidemiology:
- 1 in 700 newborns
trisomy 18 (edwards syndrome)
clinical manifestations:
- heart/ organ defects
- small abnormally shaped head, small jaw and mouth
- clenched fists with overlapping fingers
epidemiology:
- 1 in 5,000 births
gentic conditons with mixed inherticance patterns
depending on the condition and gene involved, the inheritance pattern can be autosomal dominant, autosomal recessive, or x linked recessive
ex. ehler-danlos syndrome
ehlers danlos syndrome
heredity collagen disorder characterized by articular hypermobility, dermal hyper plasticity, and widespread tissue fragility
epidemiology:
- combine prevalence 1 in 5,000 worldwide
- mutations in at least 20 genes
ehlers- danlos syndrome clinical manifestations
- hyperextensible skin
- fragile tissue
- poor wound healing
- joint hypermobility
- muscle weakness
- delayed motor development
- fatigue
- gait defects
- chronic pain
- increased propensity for joing subluxation
