Cytogenetics

Question 1

aneuploidy

Answer 1

an abnormal number of entire chromosomes
*can be missing or extra chromosomes

Question 2

structural abnormalities (in chromosomes)

Answer 2

involve fragments of chromosomes
*rearrangements, deletions, insertions
*phenotype depends on location, size, balance, etc

Question 3

centromere

Answer 3

the primary constriction point of a chromosome; point of attachment of spindle apparatus during mitosis/meiosis
*used as reference point when looking at chromosomes

Question 4

telomeres

Answer 4

ends of the chromosomes

Question 5

p arm of chromosome

Answer 5

short arm

Question 6

q arm of chromosome

Answer 6

long arm

Question 7

FISH (fluorescence in situ hybridization)

Answer 7

use of a fluorescently-labeled DNA probe to hybridize to target site
*can label single site or chromosomal regions, or specific chromosome centromeres
*can be performed during interphase (easier than G-banding)

Question 8

G-banding

Answer 8

looking at banding patterns on chromosomes
**requires cells to be in mitosis

Question 9

46, XX, del(5)(q13)

Answer 9

female with terminal deletion of one chromosome 5, distal to band 5q13

Question 10

inv(3)(p25q21)

Answer 10

pericentric inversion of chromosome 3 with breakpoints at p25 and q21; DNA is flipped (inverted) in between

Question 11

46, XX, t(2;8)(q22;p21)

Answer 11

female with balanced translocation between chromosomes 2 and 8, with breaks in bands 2q22 and 8p21

Question 12

47, XX, +21

Answer 12

female with trisomy 21 (gain of chromosome 21)

Question 13

45, XY, -22

Answer 13

male with monosomy 22 (loss of chromosome 22)

Question 14

mechanism for aneuploidy

Answer 14

caused by nondisjunction events in meiosis I (more common) or meiosis II
-resulting gametes will have incorrect number of 1 chromosome

Question 15

balanced structural rearrangements

Answer 15

all genetic material is maintained (no missing, no extra); often do not lead to problems in individual, but do in the gametes
*translocations or inversions

Question 16

unbalanced structural rearrangements

Answer 16

additional or missing genetic material

Question 17

reciprocal translocations

Answer 17

2 nonhomologous chromosomes swap DNA
-individuals usually unaffected, but increased risk in gametes

Question 18

Robertsonian translocations

Answer 18

*involve the acrocentric chromosomes (13, 14, 15, 21, 22) and only the p arms are lost
*the ends of 2 chromosomes fuse together
*considered a balanced translocation, even though karyotype is 45, XX or 45, XY
(46 in a robertsonian translocation in UNBALANCED)

Question 19

chromosome inversions

Answer 19

portion of the chromosome is inverted without a loss of material (balanced)

Question 20

paracentric inversion

Answer 20

within one arm; does NOT involved the centromere

Question 21

pericentric inversion

Answer 21

involves both arms; contains the centromere; often problematic for the gametes

Question 22

philadelphia chromosome

Answer 22

translocation common in chronic myelogenous leukemia (CML) b/w ch9 and ch22; breaks within 2 genes and creates a new oncogene that leads to uncontrolled growth