Genetics

Question 1

3 primary types of mutations

Answer 1

• genome mutation
• chromosomal mutations
• gene variant

Question 2

genome mutation

Answer 2

loss or gain of an entire chromosome

Question 3

chromosomal mutation

Answer 3

alteration of a segment of chromosome

Question 4

gene variant

Answer 4

partial or complete deletion of a gene

Question 5

chromosomes

Answer 5

long chain DNA

Question 6

genes

Answer 6

segment of DNA

Question 7

human typical chromosomes and pairs

Answer 7

• 46 chromosomes
• 23 pairs
• 22 pairs of autosomal chromosomes
• 1 pair of sex chromosomes

Question 8

hereditary or familial

Answer 8

condition derived from parents due to a genetic mutation

Question 9

congenital

Answer 9

condition present at birth
- may be hereditary or derived from action or exposure during pregnancy or birth

Question 10

not all hereditary conditions are congenital? true or false

Answer 10

true

Question 11

not all congenital conditions are hereditary? true or false

Answer 11

true

Question 12

types of inheritance patterns

Answer 12

• autosomal dominant
• autosomal recessive
• x-linked recessive
• chromosomal
• genetic conditions with mixed inheritance patterns

Question 13

autosomal dominant

Answer 13

the gene in question is located on one of the 44 numbered, or non-sex chromosomes

Question 14

autosomal dominant

Answer 14

a single copy of the mutated gene is enough to cause phenotypic expression

Question 15

autosomal dominant mutation

Answer 15

low density lipoprotein (LDL)
- receptor mutation that results in impaired uptake of cholesterol into cells

Question 16

autosomal dominant clinical manifestations

Answer 16

• elevated blood cholesterol levels
• atherosclerosis resulting in cardiovascular disease
  -death before the age of 30 due to uncontrolled CVD

Question 17

autosomal dominant: marfan syndrome

Answer 17

• mutation: 1 geen on chromosome 15q21
  -fibrillin provides support for production of elastic fibers

Question 18

clinical manifestation: marfan syndrome

Answer 18

• skeletal: long arms, legs, and fingers
• eye: bilateral dislocation of the lens
• cardiovascular: aortic root dilation leading to aortic insufficiency

Question 19

osteogenesis imperfecta

Answer 19

• autosomal dominant ~ 80%
• autosomal recessive ~ 20%
• heterogeneous
• pleiotropic

Question 20

pleiotropic

Answer 20

one gene influence 2 phenotypic traits

Question 21

90% of osteogensis imperfects cases are caused by?

Answer 21

the mutation of the COL1A1 or COL1A2 genes
- both of these genes encode type 1 collagen

Question 22

osteogenesis imperfecta type 1

Answer 22

mild:
- short stature
- postnatal fractures
- little or no deformity
- blue scleras (blue in the whites of eye)
- premature hearing loss

Question 23

osteogenesis imperfecta type 2

Answer 23

perinatal lethal: LIFE THREATENING
- severe prenatal fractures
- abnormal bone formation
- severe deformities
- blue scleras
- connective tissue fragility

~ most severe

Question 24

osteogenesis imperfecta type 3

Answer 24

progressive deforming:
- prenatal fractures
- deformities usually present at birth
- very short stature
- usually nonambulatory
- blue scleras
- hearing loss

Question 25

osteogenesis imperfecta type 4

Answer 25

deforming with normal scleras:
- postnatal fractures
- mild to moderate deformities
- premature hearing loss
- normal or gray scleras
- dental abnormalities imperfect

Question 26

osteogenesis imperfecta

Answer 26

• 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

Question 27

osteogenesis imperfecta pathophysiology

Answer 27

disease of the type 1 collagen: major extraceullular protein in the body
ex.
- dermis
- connective tissue of the organs, GI, and vascular system
- bones

Question 28

severity of osteogenesis imperfecta

Answer 28

type 1 < type 4 < type 3 < type 2

Question 29

autosomal recessive

Answer 29

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

Question 30

autosomal recessive: cystic fibrosis

Answer 30

mutation: cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7

• epidemiology: 1 in 3500 live births; white predominantly

Question 31

clinical manifestations of cystic fibrosis

Answer 31

• 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

Question 32

why is there increased concentration of chloride in sweat in cystic fibrosis patients?

Answer 32

due to inability of chloride to move in and out of cells

Question 33

x-linked recessive

Answer 33

refers to genetic conditions associated with mutation in genes on an X chromosome

ex. duchenne muscular dystrophy

Question 34

x linked recessive: duchenne muscular dystrophy

Answer 34

• mutations: dystrophin gene at Xp21
• epidemiology: 1 in 3000 infants; profound in male and female carriers are typically asymptomatic

Question 35

clinical course of muscular dystrophy

Answer 35

• 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

Question 36

clinical manifestations signs and symptoms: muscular dystrophy

Answer 36

• 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

Question 37

chromosomal inheritance pattern

Answer 37

mutation of a large segment or entire chromosome

ex.
- down syndrome
- trisomy 18

Question 38

down syndrome

Answer 38

• 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

Question 39

trisomy 18 (edwards syndrome)

Answer 39

clinical manifestations:
- heart/ organ defects
- small abnormally shaped head, small jaw and mouth
- clenched fists with overlapping fingers

epidemiology:
- 1 in 5,000 births

Question 40

gentic conditons with mixed inherticance patterns

Answer 40

depending on the condition and gene involved, the inheritance pattern can be autosomal dominant, autosomal recessive, or x linked recessive

ex. ehler-danlos syndrome

Question 41

ehlers danlos syndrome

Answer 41

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

Question 42

ehlers- danlos syndrome clinical manifestations

Answer 42

• hyperextensible skin
• fragile tissue
• poor wound healing
• joint hypermobility
• muscle weakness
• delayed motor development
• fatigue
• gait defects
• chronic pain
• increased propensity for joing subluxation