Karyotype, Aneuploidy, and nondisjunction Flashcards
Numerical Chromosomal abnormalities may be a result of?
Non-disjunction during meiosis
Non-disjunction during mitosis
Mosaicism
Structural Chromosomal Abnormalities may arise from?
Deletions
duplications
inversions
translocations
isochromosomes
Ring Chromosomes
what can be detected by Karyotyping?
can detect deletions, duplications, inversions, translocation
Deletions larger than what are visible by standard Karyotypes?
5 Mb
What is this an image of ?

Metacentric
What is this an image of ?

Submetacentric
What is this an image of ?

Acrocentric
Interphase FISH
Rapid testing
Avoids need for cell culturing
Chromosomes are decondensed in the nucleus
Metaphase FISH
Has to be cultured
usually done after G-banding karyotype
Gives location information because the banding pattern would be known
Euploidy-Triploidy
contain three chromosomes
not compatible with life
euploidy-Tetraploidy
Contain four copies of chromosomes
lethal
Aneuploidy trisomies compatible with life
Trisomy 21 Down syndrome
Trisomy 18 Edwards
Trisomy 13 Patau
Sex chromosome Aneuploidy
Turner Syndrome( 45,X) Klinefelter (47,XXY)
Risk factors for Trisomy 21 Down syndrome
Increased Maternal Age
Increases risk for meitotic nondisjunction during oogenesis
Most common is meiosis I nondisjunction
Features of Trisomy 21 (down syndrome)
- 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
What disease is shown by this karyotype?

trisomy 21
What disease is shown by this FISH

trisomy 21
What disease is shown by this CGH

trisomy 21
Mechanism of Trisomy 18(Edwards Syndrome)
nondisjunction during oogenesis
Features of Trisomy 18 (Edwards Syndrome)
- Clenched fists or overlapping fingers
- Rocker bottom feet
- Congenital heart defects
- Low-set ears, smaller lower jaw
- Microcephaly
- Intellectual disability

What disease is shown by this Karyotype

trisomy 18 ( Edwards Syndrome)
What disease is shown by this CGH

Trisomy 18 (Edwards Syndrome)
Trisomy 13 (Patau Syndrome)
common mechanism is nondisjunction during oogenesis
Features of Trisomy 13 (Pataus Syndrome)
- Polydactyly
- Cleft lip and palate
- Microphthalmia
- Microcephaly
- Intellectual Disability
- Cardiac Anomalies

What disease is shown by this Karyotype

trisomy 13 (Patau syndrome)
What disease is shown by this CGH

Trisomy 13 (Patau Syndrome)
Turner syndrome (45,X)
X chromosome Monosomy
due to nondisjunction during Spermatogenesis
features of Turner syndrome
- Webbed neck and neck swelling at birth(cystic hygroma)
- Primary amenorrhea
- Gonadal Dysgenesis
- Streak ovaries
- Lymphoedema of hands and feet
What disease is shown by this Karyotype

Turner Syndrome(45,X)
What disease is shown by this CGH

Turner Syndrome (45,X)
Mosaic Turner syndrome - not phenotypic
- Fertillized egg could have been 46,XX
- Mitotic nondisjunction during embryogenesis
- Some cells are 45,X others are : 46,XX 47,XXX
Mosaic Turner syndrome -phenotypic
- 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
Klinefelter syndrome 47,XXY
Genetic mechanism : nondisjunction during meiosis
mosaic : 46XY/47XXY/48XXXY
Features of Klinefelter syndrome for a male(47,XXY)
- Gyncecomastia
- Female distribution of hair
- infertility ad testicular atrophy due to low levels of testosterone
- Feminization of features
What disease is shown by this Karyotype?

Klinefelter syndrome
What disease is shown by this CGH

Klinefelter Syndrome
What is the mechanism for Mosaicism?
Mitotic disjunction
2 ways that a person could be mosaic for a down syndrome
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