Structural Chromosomal Abnormality

Question 1

Chronic Myelogenous Leukemia

Answer 1

Reciprocal Chromosome Translocation btw abnormal chromosome 9 and Philadelphia Chromosome.

Question 2

Pericentric inversion

Answer 2

span centromere

Question 3

paracentric inversion

Answer 3

no centromere contained

Question 4

Balanced normal complement of chromosomal material (still have some disorders)

Answer 4

inversion, reciprocal translocation, robertsonian translocation

Question 5

Reciprocal Translocation

Answer 5

Alternate( usually normal)
Adjacent-1
Adjacent-2
-quadrivalent

Question 6

Robertsonian Translocation

Answer 6

• two acrocenteric chromosomes losing short arms (lose satellite sequence and stalk) and joint together
• Der
• lose one chromosome, still balanced
• trivalent

Question 7

Robertsonian Translocation Disorder

Answer 7

Trisomy 21

• 46 chromosome but Trisomy 21
• Robertsonian Translocation- no maternal age contribution

Question 8

Unbalanced abnormal chromosomal content

Answer 8

Deletions
Duplications
Isochromosomes
Marker (ring) chromosomes

Question 9

Isochromosome

Answer 9

• chromosome which one arm is missing and the other arm is duplicated in mirror-fashion
• 100% of the viable offspring of a carrier isochromosome 21 will be down syndrome

Question 10

Down syndrome mechanism

Answer 10

meiosis I nondisjunction (95%)(maternal)
Robertsonian translocation (4%)
Isochromosme
Mosiac down syndrome
Partial trisomy 21 (very rare)

Question 11

Charcot-Marie-Tooth (CMT 1A1)

Answer 11

duplication of the gene for peripheral myelin protein -22,17p11.2

• 1/2500 inherited neurological disorder
• weakness of foot, lower leg muscles, hammertoes, weakness and atrophy of hands later
• peripheral nerve Mal-function

Question 12

Hereditary neuropathy with liability to pressure palsies

Answer 12

deletion of the gene encoding peripheral myelin protein- 22,17p11.2

Question 13

Hereditary neuropathy with predispostion to pressure palsy (HNPP)

Answer 13

Deletion of PMP- 22

opposite mech from charcot-marie-tooth diease

Question 14

Contiguous gene syndrome

Answer 14

abnormal phenotype caused by over-expression or loss (haploinsufficiency) of neighboring genes

Question 15

Velocardiofacial syndrome

Answer 15

• contiguous gene syndrome
• del 22q11
• cleft palate, septal defects
• defect in conotruncal region of heart

Question 16

DiGeorge syndrome

Answer 16

• Contigous gene syndrome
• del 22q11
• neural crest, branchial pouches, great vessels
• overflow tract defects in the heart