FTM 54-55 - Cytogenetics 1 & 2

Question 1

What letter designation is given to the long and short arms of a chromosome?

Answer 1

p - short arm

q - long arm

Question 2

Define Euploidy and Aneuploidy

Answer 2

Question 3

What are the chromosomal aneuploidy syndromes we need to know?

Answer 3

Question 4

Facts to know about Down Syndrome

Answer 4

Question 5

What are epicanthal folds?

Answer 5

Question 6

What is a palpebral fissure?

Answer 6

Question 7

Facts to know about Edward Syndrome.

Answer 7

Question 8

What are rocker bottom feet?

Answer 8

Feet where the arch of the foot is convex instead of concave, like the legs of a rocking chair.

Question 9

Facts to know about Patau syndrome

Answer 9

Question 10

What is microphthalmia?

Answer 10

A developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eyes are abnormally small and have anatomic malformations.

Question 11

Facts to know about turner syndrome

Answer 11

Question 12

What is amenorrhea?

Answer 12

The absence of menstruation — one or more missed menstrual periods. Women who have missed at least three menstrual periods in a row have amenorrhea, as do girls who haven’t begun menstruation by age 15.

Question 13

What can cause Turner Syndrome besides nondisjunction?

Answer 13

Question 14

Facts to know about Klinefelter syndrome

Answer 14

Question 15

Answer 15

3

Question 16

When and where is nondisjunction most common?

Answer 16

During meiosis-I in females

Question 17

What types of nondisjunction can cause Klinefelter syndrome, an XYY syndrome, and triple X syndrome?

Answer 17

Question 18

What causes mosaicism?

Answer 18

Post-zygotic non-disjunction (during embryonic development)

Question 19

Answer 19

B

Question 20

List and describe the types of structural chromosomal abnormalities.

Answer 20

Reciprocal Translocation - exchange of genetic material between non-homologous chromosomes

Robertsonian Translocation - when the participating chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere. Usually occurs with the acrosomal chromosomes

Deletions

Inversions - a segment of a chromosome is reversed end to end

Isochromosomes - one arm is lost and the other is duplicated

Ring Chromosomes - the terminal portions of a chromosome fuse

Question 21

What are some common consequences of a reciprocal translocation?

Answer 21

When it occurs in somatic cells there is an increased risk of the cells becoming cancerous or there may be no effect at all

When it occurs in germ line cells there is a higher risk for spontaneous abortions in the carrier

Question 22

What are some common ways that a reciprocal translocation can lead to cancer?

Answer 22

Question 23

Answer 23

2

Question 24

Which chromsomes are acrocentric?

Answer 24

13, 14, 15, 21, 22

Question 25

Describe how a robertsonian translocation takes place.

Answer 25

Question 26

Is robertsonian translocation balanced or unbalanced?

Answer 26

Either it depends on how the chromosomes segregate during meiosis

Question 27

What are the effects of Robertsonian translocations on gametes?

Answer 27

Question 28

Answer 28

2

Question 29

What causes Cri du chat syndrome? How is it diagnosed? What are its symptoms?

Answer 29

Cri-du-chat syndrome is caused by a large deletion (\>4 Mb) on the 5th chromosome. It can be diagnosed using FISH or Array CGH. Its symptoms include a high pitched cat-like cry, severe intellectual disability, speech problems, and microcephaly.

Question 30

What causes DiGeorge syndrome? How is it diagnosed? What are its symptoms?

Answer 30

It is caused by a microdeletion of chromosome 22q. It can be diagnosed via FISH using locus specific probes or by array CGH. Common symptoms are congenital heart defects, absence of thymus, cleft lip & palate, and learning disability.

Question 31

What causes Wolf-Hirschhorn Syndrome? What are its symptoms?

Answer 31

A large deletion on chromosome 4. Common symptoms are widely spaced eyes, prominent nose, abnormal iris, cardiac anomalies, and intellectual/developmental delay.

Question 32

What causes WAGR syndrome? What are its symptoms?

Answer 32

WAGR syndrome is caused by a microdeletion on chromosome 11. Its common symptoms lend the disease its name: Wilms' tumor, aniridia (the absence of the iris), genitourinary malformations, and retardation of growth/development.

Question 33

Facts to know about the genetics of Angelman Syndrome and Prader-Wili Syndrome.

Answer 33

Question 34

What are the symptoms of Prader-Willi syndrome and Angelman syndrome?

Answer 34

Question 35

What are pericentric and paracentric inversions?

Answer 35

Pericentric inversions involve the centromere and paracentric inversions do not.

Question 36

Are inversions usually balanced or unbalanced? What does this mean clinically?

Answer 36

They are usually balanced meaning there are typically no clinical problems

Question 37

How can inversions be detected and why?

Answer 37

Question 38

What are the effects of chromosomal inversions during crossover in meiosis?

Answer 38

Question 39

Answer 39

1 The mother failed to separate 1 and 2 which means meiosis 1 nondisjunction