Chapter 3 ( Cytogenics ) Flashcards

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1
Q

G banding ?

A

Mitotic chromosomes are partially digested with trypsin and then stained with Giemsa

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2
Q

Acrocentric chromosomes ?

A

13-14-15-21-22

Which are the only chromosomes involved in Robertsonian translocation

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3
Q

Autosomal monosomies ?

A

All are inconsistent with a live birth

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4
Q

Autosomal trisomies ?

A

Only 3 are consistent with a live birth which are : 13 - 18 - 21

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5
Q

Down syndrome ?

A
Trisomy 21 
Mental retardation 
Short stature 
Hypotonia 
Depressed nasal bridge 
Upslanting palpebral fissure , epicanthal fold 
Congenital heart defects 
Reduced fertility
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6
Q

Edward syndrome ?

A
18 trisomy 
Clenched fist with overlapping fingers 
Low set ears 
Micrognathia 
Mental retardation 
Inward turning 
Congenital heart defects
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7
Q

Patau syndrome ?

A
Trisomy 13 
Polydactyly 
Cleft lip and cleft palate 
Microphthalmia 
Microcephaly and mental retardation 
Cardiac and renal defects
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8
Q

Klinefelter syndrome ?

A
Sex chromosome aneuploidy 
47,XXY
Testicular atrophy 
Infertility 
Gynecomastia 
Female distribution of hair 
High pitched voice
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9
Q

Turner syndrome ?

A

The only monosomy consistent with life
45,X
50% of cells are 45,X
Majority of others are mosaics for 45,X and one other cell lineage
Short stature
Cystic hygroma in utero resulting in excess nuchal skin and webbed neck
Primary amenorrhea
Infertility
Edema of wrist and ankles in new borns
Coarctation of aorta and other congenital heart defects

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10
Q

Prenatal triple screen ?

A

Prenatal screening for down syndrome by assessing the serum levels of
1- alpha fetoprotein
2- chorionic gonadotropin
3- unconjugated estriol
Which can detect 70% of fetuses with down

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11
Q

Types of chromosomal translocations ?

A

1- Reciprocal translocation : when genetic material is exchanged between two homologous chromosomes .
2- Robertsonian translocation : occurs only in acrocentric chromosomes and involves loss of short arms of two of the chromosomes and subsequent fusion of the long arms .

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12
Q

Alternate and adjacent segregation ?

A

Alternate segregation : chromosomes from alternate quadrants enter a gamete
Adjacent segregation : chromosomes from adjacent quadrants enter a gamete

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13
Q

Reciprocal translocations involving oncogenes ?

A

t(9;22) Chronic myelogenous leukemia (c-abl)
t(8;14) Burkitt lymphoma (c-myc)
t(15;17) Acute myelogenous leukemia (retinoid recepor alpha)
t(14;18) Follicular lymphomas (bcl-2 that inhibit apoptosis)
t(11;14) Mantle cell lymphoma (cyclin D)

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14
Q

Cri-du-chat syndrome ?

A

Caused by interstitial or terminal deletion of 5p ( short arm of chromosome 5 )
High-pitched cat like cry
Microcephaly and mental retardation
Congenital heart disease

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15
Q

Examples for microdeletions ?

A
Parder-Willi syndrome 
Angelman syndrome 
DiGeorge syndrome 
Wilms tumor 
Williams syndrome
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16
Q

Williams syndrome ?

A

Hypercalcemia
Supravalvular aortic stenosis
Mental retardation
Characteristic face

17
Q

DiGeorge syndrome ?

A
Congenital absence of the thymus and parathyroids 
Hypocalcemic tetany 
T-cell immunodeficiency 
Characteristic face with cleft palate 
Heart defects
18
Q

The only example for isochromosome that’s compatible with live birth ?

A

Turner syndrome 46,X,i(Xq)
Which is the cause of 22% of Turner cases
The other 78% have 45,X monosomy due to nondisjunction

19
Q

Fluorescence in situ Hybridization (FISH) uses and advantages ?

A

Used to detects ; aneuploidies , translocations , deletions

Advantage : the chromosomes don’t have to be in the metaphase stage for accurate diagnosis

20
Q

Uses of Spectral Karyotyping ?

A

Visualization of chromosome rearrangements such as small translocations
Example : Philadelphia chromosome rearrangement t(9;22) in CML

21
Q

Direct genetic testing and indirect genetic testing types ?

A

Direct genetic testing :
1- PCR and ASO probes
2- RFLP analysis of PCR product
3- Direct DNA sequencing

Indirect genetic testing :
1- using STRPs
2- using RFLPs