Ch 5: Genetics

Question 1

what are polymorphisms

Answer 1

genetic variations

Question 2

what is a mutation

Answer 2

permanent change in DNA

Question 3

what is an inherited (familial) disease

Answer 3

inherited chromosomal abnormality of one or more parents

Question 4

what is Marfan Syndrome

Answer 4

dominant, inherited defect in the FBN1 gene encoding the extracellular glycoprotein fibrillin-1
prevents TGF-b which causes bone overgrowth
causes skeletal abnormalities, ocular changes (lens dislocation), and cardiovascular lesions (mitral valve prolapse)

Question 5

what does fibrilin-1 do

Answer 5

glycoprotein that is a major component of microfibrils found in the extracellular matrix and forms elastic fibers

Question 6

what is Ehlers-Danlos Syndome

Answer 6

dominant disorder that causes mutations in genes that encode for collagen and its modifying enzymes
effects skin (hyperextensible), joints (hyperextensible), bowl (rupture), and large vessels

Question 7

what is familial hypercholesterolemia (FH)

Answer 7

dominant disorder that impairs hepatic clearance of LDL
leads to increased serum cholesterol levels which causes premature atherosclerosis
cholesterol deposits along tendon sheaths

Question 8

what is a xanthoma

Answer 8

papule or nodule typically in tendon sheaths due to lipid deposits
under the microscope, cells are light and have a foamy protoplasm (foam cells)

Question 9

which organelle is the key component of the intracellular digestive system

Answer 9

lysosome

Question 10

what is Tay-Sachs Disease

Answer 10

recessive disease where there is a mutation on chromosome 15 which causes severe deficiency of hexosaminidase A
GM2 gangliosides (lipids) cannot be catabolized so they build up in the nerve cells
prevalent in Ashkenazic Jews
presents with cherry red spots in retina, motor and mental deterioration, and dementia
leads to a complete vegetative state

Question 11

what is Sandhoff Disease

Answer 11

recessive deficiency of hexosaminidase B (HEXB) which results in neuronal injury and also affects the liver, pancreas, and kidney

Question 12

what is Neimann-Pick Disease (type A/B)

Answer 12

recessive disorder where there is a lysosomal accumulation of sphingomyelin due to inherited deficiency in sphingomyelinase
common in Ashkenazi Jews
affected cells (lipid-laden phagocytic foam cells) become enlarged due to distended lysosomes (occurs in spleen, liver, lymph nodes, bone marrow, etc.)
type A: early death in first 3 years of life due to CNS involvement
type B: organomegaly, no CNS involement

Question 13

what is Neimann-Pick Disease (type C)

Answer 13

most common out of the three types
primary defect in nonenzymatic lipid transport (transport of free cholesterol from lysosomes to cytoplasm)
at birth: hydrops fetalis (severe swelling), hepatitis, and neurologic damage

Question 14

what is Guacher Disease

Answer 14

most common type of lysosomal storage disorder
recessive disease where there is a mutation in the glucocerebrosidase
this causes glucocerebrosides (lipids in nerve sheaths) to accumulate in macrophages leading to Guacher cells
type 1: affects spleen and bone marrow
type 2+3: affects CNS
high probability of causing Parkinson due to the disease leading to the accumulation of synucleins (brain proteins)

Question 15

what are Guacher cells

Answer 15

enlarged macrophages due to the presence of distended lysosomes which are filled with glucocerbrosides
start to resemble wrinkled tissue paper

Question 16

what is Von Gierke Disease (type 1)

Answer 16

mutation in the glucose-6-phophatase when leads to an accumulation of glycogen in the liver
leads to reduction of blood glucose concentrations (hypoglycemia)

Question 17

what is mcardle disease (type 5)

Answer 17

deficiency or complete absence of the muscle glycogen phosphorylase enzyme
leads to a disregulation of glucose metabolism in muscles
presents with painful muscle cramps, weakness, etc.

Question 18

what is pompe disease (type 3)

Answer 18

glycogen storage disease where glycogen is not broken down so it accumulates in the skeletal muscle fibers

Question 19

what is karyotping

Answer 19

the study of chromosomes typically by a cytogenetiscist

Question 20

define euploid

Answer 20

any exact multiple of the haploid number of chromosomes (23, 46, 69, etc)

Question 21

define aneuploidy

Answer 21

error occurs in meiosis or mitosis which causes a cell to have a number of chromosomes that is not a multiple of 23

Question 22

decode 47,XY,+21

Answer 22

male with 47 chromsomes, one extra 21st

Question 23

define inversion in terms of a mutation

Answer 23

rearrangment where a single chromosome is broken then reincorporated backwards

Question 24

define translocation

Answer 24

segment of chromosome is transferred to another

Question 25

what percentage of all conceptions have a chromosomal abnormality

Answer 25

7.5%

Question 26

what is trisomy 21

Answer 26

down syndrome - most common chromosomal disorder
extra 21st chromosome
presents with: congenital heart disease (atrioventricular septal defect), neuropathic changes (Alzheimers), short A-P diameter, and open operculum (recessed area in brain)

Question 27

what is trisomy 13

Answer 27

patau syndrome
extra 13th chromosome
presents with: midline facial defects (cleft lip & palate), hypotelorism (wideset eyes), midface hypoplasia (abnormal development), polydactyly, micropthalmia (decreased size of eyeball)

Question 28

what is trisomy 18

Answer 28

Edwards syndrome
extra 18th chromosome
presents with: low-set ears, upturned nares, micrognathia (recessed lower jaw), overlapping fingers, rockerbottom feet, horseshoe kidney, and valvular dysplasia

Question 29

what is cri du chat syndrome

Answer 29

cat cry syndrome
partial deletion of short arm of chromosome 5
presents with: round oval face, catlike cry, and growth and mental retardation

Question 30

what is triploidy

Answer 30

69 chromosomes - not compatible with life
presents with: hydrocephalus, low set ears, hypertelorism (wide set eyes), bulbous nose, sloping forehead, syndactyly (webbed), and camptodactyly (fixed bent position)

Question 31

what is monosomy X

Answer 31

turner syndome - a female who is missing a X chromosome
presents with: cystic hygroma (lymphatic malformation), webbing of the neck, underdeveloped or absence of ovaries, and contraction of heart vessels

Question 32

what is klinefelter syndrome

Answer 32

males that have and extra X chromosome for a total of 3 sex chromosomes
presents with: gynecomastia, small penis and testis, long legs, etc.

Question 33

what is fragile X syndrome and what does it present with

Answer 33

martin-bell syndrome
most common genetic cause of intellectual disabilities in males
piece of the X chromosome breaks off
presents with: pectus excavatum, elongated face, large ears, and intellectual disabilities

Question 34

how should samples for cytogenetics be taken

Answer 34

using sterile techniques such as sterile saline instead of alcohols

Question 35

where are the best sources for cytogenetics tissue

Answer 35

fascia, lung, achilles tendon, chorionic villi, and cartilage