Karyotype, Aneuploidy, and nondisjunction

Question 1

Numerical Chromosomal abnormalities may be a result of?

Answer 1

Non-disjunction during meiosis
Non-disjunction during mitosis
Mosaicism

Question 2

Structural Chromosomal Abnormalities may arise from?

Answer 2

Deletions
duplications
inversions
translocations
isochromosomes
Ring Chromosomes

Question 3

what can be detected by Karyotyping?

Answer 3

can detect deletions, duplications, inversions, translocation

Question 4

Deletions larger than what are visible by standard Karyotypes?

Answer 4

5 Mb

Question 5

What is this an image of ?

Answer 5

Metacentric

Question 6

What is this an image of ?

Answer 6

Submetacentric

Question 7

What is this an image of ?

Answer 7

Acrocentric

Question 8

Interphase FISH

Answer 8

Rapid testing
Avoids need for cell culturing
Chromosomes are decondensed in the nucleus

Question 9

Metaphase FISH

Answer 9

Has to be cultured

usually done after G-banding karyotype

Gives location information because the banding pattern would be known

Question 10

Euploidy-Triploidy

Answer 10

contain three chromosomes
not compatible with life

Question 11

euploidy-Tetraploidy

Answer 11

Contain four copies of chromosomes
lethal

Question 12

Aneuploidy trisomies compatible with life

Answer 12

Trisomy 21 Down syndrome
Trisomy 18 Edwards
Trisomy 13 Patau

Question 13

Sex chromosome Aneuploidy

Answer 13

Turner Syndrome( 45,X) 
Klinefelter (47,XXY)

Question 14

Risk factors for Trisomy 21 Down syndrome

Answer 14

Increased Maternal Age

Increases risk for meitotic nondisjunction during oogenesis

Most common is meiosis I nondisjunction

Question 15

Features of Trisomy 21 (down syndrome)

Answer 15

• Intellectual disability
• short stature
• Depressed nasal bridge
• upslanting palpebral fissures
• epicanthal folds
• congenital heart defects
• single palmar crease
• develop changes similar to Alzheimers disease at a relatively young age

Question 16

What disease is shown by this karyotype?

Answer 16

trisomy 21

Question 17

What disease is shown by this FISH

Answer 17

trisomy 21

Question 18

What disease is shown by this CGH

Answer 18

trisomy 21

Question 19

Mechanism of Trisomy 18(Edwards Syndrome)

Answer 19

nondisjunction during oogenesis

Question 20

Features of Trisomy 18 (Edwards Syndrome)

Answer 20

• Clenched fists or overlapping fingers
• Rocker bottom feet
• Congenital heart defects
• Low-set ears, smaller lower jaw
• Microcephaly
• Intellectual disability

Question 21

What disease is shown by this Karyotype

Answer 21

trisomy 18 ( Edwards Syndrome)

Question 22

What disease is shown by this CGH

Answer 22

Trisomy 18 (Edwards Syndrome)

Question 23

Trisomy 13 (Patau Syndrome)

Answer 23

common mechanism is nondisjunction during oogenesis

Question 24

Features of Trisomy 13 (Pataus Syndrome)

Answer 24

• Polydactyly
• Cleft lip and palate
• Microphthalmia
• Microcephaly
• Intellectual Disability
• Cardiac Anomalies

Question 25

What disease is shown by this Karyotype

Answer 25

trisomy 13 (Patau syndrome)

Question 26

What disease is shown by this CGH

Answer 26

Trisomy 13 (Patau Syndrome)

Question 27

Turner syndrome (45,X)

Answer 27

X chromosome Monosomy due to nondisjunction during Spermatogenesis

Question 28

features of Turner syndrome

Answer 28

* Webbed neck and neck swelling at birth(cystic hygroma) * Primary amenorrhea * Gonadal Dysgenesis * Streak ovaries * Lymphoedema of hands and feet

Question 29

What disease is shown by this Karyotype

Answer 29

Turner Syndrome(45,X)

Question 30

What disease is shown by this CGH

Answer 30

Turner Syndrome (45,X)

Question 31

Mosaic Turner syndrome - not phenotypic

Answer 31

* Fertillized egg could have been 46,XX * Mitotic nondisjunction during embryogenesis * Some cells are 45,X others are : 46,XX 47,XXX

Question 32

Mosaic Turner syndrome -phenotypic

Answer 32

* Fertilized egg 46, XY * Mitotic Nondisjunction during embryogenesis * Some Cells are 45,X others 46 XY * Mosaic 45,X/ 46XY are recommended for oophorectomy due to risk of gonadoblastoma

Question 33

Klinefelter syndrome 47,XXY

Answer 33

Genetic mechanism : nondisjunction during meiosis mosaic : 46XY/47XXY/48XXXY

Question 34

Features of Klinefelter syndrome for a male(47,XXY)

Answer 34

* Gyncecomastia * Female distribution of hair * infertility ad testicular atrophy due to low levels of testosterone * Feminization of features

Question 35

What disease is shown by this Karyotype?

Answer 35

Klinefelter syndrome

Question 36

What disease is shown by this CGH

Answer 36

Klinefelter Syndrome

Question 37

What is the mechanism for Mosaicism?

Answer 37

Mitotic disjunction

Question 38

2 ways that a person could be mosaic for a down syndrome

Answer 38

non-disjunction may occur as a post-zygotic event during embryonic development * Trisomy Rescue: fetus has 2 cell types * Non-disjunction may occur in the ovum during oogenesis and fertilization by a normal sperm leads to trisomy 21 in the conception * During the post-fertilization mitosis one of the extra chromosome 21 is evicted during cell division