Cytogenetics

Question 1

What is cytogenetics?

Answer 1

The study of chromosomes and their structure, inheritance, and abnormalities

Question 2

Which arm of the chromosome is the long arm? Which is the short arm?

Answer 2

Long= q; short= p

Question 3

During which stage of mitosis are chromosomes best visualized?

Answer 3

Metaphase

Question 4

Which class of chromosome structure has the centromere directly in the center of the chromosome?

Answer 4

Metacentric

Question 5

Which human chromosomes are telocentric?

Answer 5

None

Question 6

What class of chromosome structure has the centromere very near the end of the chromosome?

Answer 6

Acrocentric

Question 7

What technique enables the identification of individual chromosomes by producing characteristic light and dark bands?

Answer 7

G-banding

Question 8

What are the two types of chromatin visualized via G-banding?

Answer 8

Dark staining= Heterochromatin; Light gray or white= euchromatin

Question 9

What is the name of the lab techniqu in which fluorescently labeled fragment of cloned DNA (probe) is allowed to pair with its complementary sequence on the chromosome directly on the microscope slide

Answer 9

Fluorescence in situ hybridization

Question 10

What is polyploidy?

Answer 10

Any abnormal multiple of the haploid chromosome number

Question 11

What is aneuploidy?

Answer 11

Any number of chromosomes that is not diploid

Question 12

What is the most common cause of aneuploidy?

Answer 12

Nondisjunction

Question 13

What is the most common cause of triploidy?

Answer 13

Simultaneous fertilization of one egg by two sperm

Question 14

What is the chromosomal basis of Down Syndrome?

Answer 14

Trisomy 21

Question 15

What is the most common trisomy?

Answer 15

Trisomy 21

Question 16

What are the principle features of Down Syndrome?

Answer 16

Flat facial profile, prominent epicanthal folds, cardiac structural defects, GI obstructions, Early onset Alzheimer’s, hearing deficits

Question 17

What chromosomal abnormaility is the basis of Patau Syndrome?

Answer 17

Trisomy 13

Question 18

What symtoms/ features are associated with Trisomy 13?

Answer 18

Cleft lip/palate, congenital heart defects, incomplete brain development (holoprocencephaly), apneic spells, polydactyly, low set deformed ears

Question 19

What is the chromosomal basis of Edwards Syndrome?

Answer 19

Trisomy 18

Question 20

What are the common clinical features of trisomy 18?

Answer 20

Clenched hand, deformed digits, rocker bottom feet, low set malformed ears, short sternum, congenital heart defects

Question 21

What is the karyotype associated with Turner syndrome?

Answer 21

45, X

Question 22

What is the typical presentation of Turner Syndrome?

Answer 22

Very short stature, absent/abnormal ovaries, sterility, broad chest, lymphedemia–> webbed-neck, bone anomalies

Question 23

What karyotype is associated with Klinefelter Syndrome?

Answer 23

47, XXY

Question 24

What are the common clinicial features of Klinefelter Syndrome?

Answer 24

Males w/ infertility, small penis and testes, enlarged breasts, sparse body/facial hair, tall stature, long limbs, dull mentality/behavioral problems/ learning difficulties/ austism common

Question 25

What causes mosaicism?

Answer 25

Nondisjunction after conception

Question 26

What is the basis of Cri du Chat syndrome?

Answer 26

deletion of the short arm of chromosome 5 (5p-)

Question 27

What are the features associated with Cri du Chat?

Answer 27

Low birth weight, slow growth, microcephaly, mental deficiency, abnormal facial features, enlarged tongue

Question 28

What is a balanced translocation?

Answer 28

A translocation in which there is an even exchange of material with no extra or missing genetic information

Question 29

Translocation 14; 21 inheritance may cause what condition?

Answer 29

Down syndrome

Question 30

What are the chances that carriers of translocation 21;21 will have an abnormal child?

Answer 30

100%- either Down syndrome or non-viable monosomy 21

Question 31

The majority of all Down syndrome patients have what karyotype?

Answer 31

47, +21

Question 32

What chromosomal changes are unique to cancer? From what are they likely derived?

Answer 32

Double minutes and homogenously staining regions; MYC oncogene amplification

Question 33

What technique is a variation of FISH that allows for the detection of copy number changes?

Answer 33

Comparative Genomic Hybridization