Structural Chromosomal abnormalities Flashcards

1
Q

Balanced

A

No gain or loss of genetic material

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2
Q

Unbalanced

A

Gain or loss of genetic material

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3
Q

Reciprocal translocation

A

Exchange of genetic material between non-homologous chromosomes

attach image from slide 8

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4
Q

What is this an image of ?

A

Balanced reciprocal translocation (chromosome 2 & 8)

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5
Q

What are the effects of reciprocal translocation in carriers?

A

May have no effect (silent)

Transformation to cancer and increased growth rate of cells

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6
Q

What if the reciprocal translocation is located in the germ line cells?

A

There is a higher incidence of spontaneous abortions in the carrier

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7
Q

Reciprocal translocation

A

Segregation at Meiosis

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8
Q

Reciprical Translocation creating a fusion gene

A

slide 13

t(9;22) –> Chronic Myelogenous Leukemia–> activation of an oncogene–> Cancer Philadelphia chromosome t(9;22)–> Activation of BCR-ABL tyrosine kinase which is a proto-oncogene in hematopoietic cells

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9
Q

Reciprocal translocation changing gene expression

A

t(8;14) —> Burkitt lymphoma Dysregulation of c-Myc gene expression, leading to cancer

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10
Q

Robertsonian translocation

A
  • Occurs between acrocentric chromosomes
    • Chromosomes 13,14,15,21,22
  • There is loss of the short arms of the two chromosomes
    • The satellite structures in the acrocentric chrome. contain multiple copies of genetic material for RNA
  • Fusion of the long arms of the two chromosomes
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11
Q

What is this an image of ?

A

Robertsonian translocation- Effects during Meiosis

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12
Q

Robertsonian translocation alternate segregation

A

Normal gamete (gamete 1)

Gamete with the derivative chromosome(gamete 2) that results in a Robertsonian translocation carrier on fertilization

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13
Q

Robertsonian translocation: adjacent segregation

A

Results in trisomy of the respective chromosome on fertilization

Gamete 3 would result in trisomy 14, that is compatible with survival, and results in spontaneous abortion

Gamete 4 would result in trisomy 21(down syndrome) on fertilization

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14
Q

What accounts for 2-5% of children with Downs syndrome?

A

Robertsonian Translocation

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15
Q

Cri-du-chat Syndrome

A

Deletion of Chromosome 5p

46,XX,del(5)(p15.3)(pter)

46,XY,del(5)(p15.3)(pter)

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16
Q

Features of Cri-du-chat Syndrome

A

High pitched, cat like cry

micrognathia which influences the cat-like cry and speech problems later in life

microcephaly

hypertelorism(widely spaced eyes)

17
Q

What is this Karyotype showing?

A

Cri-du-chat Syndrome

18
Q

What is this CGH showing?

A

Cri-du-chat Syndrome

19
Q

22q11.2 Deletion syndrome

A

Microdeletion of chromosome 22q11.2

DiGeorge syndrome, Velocardiofacial

20
Q

Features of 22q11.2 Deletion syndrome

A

congenital heart defects

absence of thymus- can cause immunological problems

Cleft lip and palate- can lead to speech difficulty

learning disability

Increased risk of schizophrenia

21
Q

Facial anomalies of 22q11.2 deletion syndrome

A

Long midface

narrow palpebral fissures

prominent nasal root

bulbus nasal tip

ear dysmorphology

22
Q

What is this CGH showing?

A

Microdeletion of chromosome 22q11.2

23
Q

What is this a FISH of ?

A

Microdeletion of chromosome 22q11.2

24
Q

Wolf-Hirschhorn syndrome

A

Deletion of ch 4p

seizures

skeletal abnormalities and congenital heart defects

spectrum of intellectual and developmental delay(mild to severe)

25
what are the facial anomalies of Wolf-Hirschhorn syndrome
Widely spaced eyes high arched eyebrows, broad and flat nasal bridge (similar to roman helmet) short philtrum downturned mouth small chin
26
Deletions in Chromosome 15q11-13
A few genes on chromosome q5 are monogenic( only one allele is expressed) SNRPN and UBE3A Prader willi and Angelman syndrome
27
Prader-willi syndrome
Deletion of Paternal chromosome 15q11-13 SNRPN
28
Angelmans syndrome
Deletion of maternal chromosome 15q11-13 UBE3A
29
Features of Prader willi
Eating disorder-hyperphagia Developmental delays hypotonia at birth hypogonadism distinctive facial features
30
Features of Angelmans syndrome
inappropriate laughing and smiling jerky uncoordinated movement lack of speech hypotonia severe developmental delay
31
Inversion abnormality
May be pEricentric ( involves the cEntromere) paracentric (does not involve the centromere) Usually result in a change in the banding pattern of the chromosome and can be identified by karyotype analysis
32
what is this an image of?
Pericentric inversion
33
what is this an image of?
paracentric inversion
34
Effects of inversion during meiosis
results in duplication or deletion of segments of the chromosome -unbalanced genetic material The gametes with acentric and dicentric chromosomes are not viable carriers of inversions may be asymptomatic but have a high risk of spontaneous abortions
35
Isochromosome
There is a loss of one arm of a chromosome and duplication of the other arm Typically results in chromosomal and gene dosage imbalance isochromosome of an autosome is lethal
36
x-isochromosome
Long arms of the X chromosome join to form an isochromosome
37
ring chromosome
Forms when a chromosome loses genetic material at the terminal portions and the ends fuse to form a ring like structure