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FTM2 > Karyotype, Aneuploidy, and Nondisjunction > Flashcards

Karyotype, Aneuploidy, and Nondisjunction Flashcards

1
Q

Classification of Chromosomes by structure

Meta, Submeta, Acrocentric

A

Metacentric: total length of chromosome

Submetacentric: Position of the centromere

Acrocentric: Presence of satellites (redundant info and can be lost)

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2
Q

Interphase FISH

A
  1. Rapid test
  2. Avoids need for cell culture
  3. Chromosomes are decondensed in the nucles
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3
Q

Metaphase stage FISH

A
  1. Must first culture the cells
  2. Usually done after G-band
  3. Gives location information because of the banding pattern would be known
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4
Q

Euploidy (polyploidy)/ Aneuploidy definition

A

Number of chromosomes are in multiples of 23.

Triploidy (69)/Tetraploidy (92)-not compatible with life

Aneuploidy: number of chromosome are not 46

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5
Q

Monosomy/Trisomy

A

Mono: Loss of a chromosome (only one that can live is Turners)

Trisomy: 13 (Patau), 18 (Edwards), 21 (Downs) are compatible with life

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6
Q

Down Syndrome: risk factors/cause/clinical features

A

Due to meiosis 1 nondisjunction in oogenesis
(may be a result of Robertsonian Translocation)

RF: increased maternal age,

  1. Intellectual disability
  2. Short stature
  3. Depressed nasal bridge, upslanting palepebral fissures, epicanthal folds
  4. Congenital heart defects
  5. Single palmar crease
  6. Develop changes similar to ALZ disease
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7
Q

Edward Syndrome: Clinical Features/Cause

Trisomy 18

A

Nondisjunction during oogenesis

  1. Clenched fist, overlapping fingers
  2. Rocker bottom feet
  3. Congenital heart defects
  4. Low-set ears, small jaw (micrognathia)
  5. Microcephaly
  6. Intellectual disability
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8
Q

Patau Syndrome: Clinical Features/Cause

A

Nondisjunction during oogenesis

  1. Polydactyly
  2. Cleft lip and palate
  3. Microphthalmia (small eyes)
  4. Microcephaly
  5. ID
  6. Cardiac anomalies (VSD or ASD)
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9
Q

Turner Syndrome: Cause/Symptoms

A

Nondisjunction during spermatogenesis

  1. Short stature
  2. Webbed neck, cystic hygroma at birth
  3. Primary amenorrhea
  4. Streak ovaries
  5. Lymphoedema of hands/feet
  6. Gondal dysgenesis
  7. Nevi spots (brown spots)

Some phenotypic females are XY mosaic. Recommended for oopherectomy d/t increased risk of gonadoblastoma

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10
Q

Klinefelter Syndrome: Cause/Symptoms

A

Nondisjunction during meisosis
May be mosaic: XY, XXY, XXXY

  1. Gynecomastia
  2. Female distribution of hair
  3. Infertility and testicular atrophy due to low levels of testosterone
  4. Feminization of features
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11
Q

Reciprocal Translocation

A

Exchange of genetic material between non-homolous chromosomes (ex: 2/8)-balanced

Effects in somatic cells: maybe be silent or increased rate of growth (cancer)

Higher incidence of spontaneous abortions if it is in the germ line cell

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12
Q

Receiprocal Translocation creating a fusion gene

A

Example: t(9;22) Philadelphia chromosome: Activation of BCR-ABL tyrosine kinase which is a proto-oncogene in hematopoietic cells that causes Chronic myelogenous leukemia

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13
Q

Reciprocal Translocation changing gene expression

A

t(8;14)-Causes Burkitt lymphoma-dysregulation of the c-Myc gene expression leading to cancer

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14
Q

Robertsonian Translocation

A

Occurs between acrocentric chromosomes (13,14,15, 21,22)

Loss of the short arms of the two chromosomes and then fusion of the long arms of two chromosomes

Accounts for 2-5% of Down Syndrome

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15
Q

What are the indications for Cytogenomic testing for a microdeletion syndrome?

A
  1. Unexplained developmental delay or autism spectrum disorder
  2. Congenital anomalies/dysmorphic features
  3. Suspected deletion or duplication syndrome
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16
Q

Cri-du-chat Syndrome: Cause/Symptoms

A

Deletion of chromosome 5p

  1. High pitched, cat-like cry
  2. Micrognathia amd speech problems
  3. Severe intellectual disability
  4. Hypertelorism (wide spaced eyes)
17
Q

22q11.2 Deletion Syndrome (DiGeorge/Velocardiofacial syndrome)

A
  1. Congenital heart defects
  2. Absence of thymus (thymic aplasia)-causes immunoligical problems
  3. Cleft lip & palate
  4. Learning disability
  5. Increased risk for schizophrenia
  6. Facial anomalies (long midface etc)
18
Q

Wolf-Hirschhorn syndrome (WHS) Cause/Symptoms

A

Deletion of ch 4p

  1. Seizures
  2. Skeletal abnormalities
  3. Spectrum of intellectual and developmental delays
  4. Facial anomalies (Roman helmet shaped forehead)
19
Q

Pericentric vs Paracentric Inversions

A

PEricentric: involes centromere
Paracentric: does not involve centromere

Carriers of inversions may be asymptomatic but have a high risk of spontaneous abortions

20
Q

Isochromosomes

A

Loss of one arm of a chromosome and a duplication of the other arm

Lethal in an autosome

20
Q

Isochromosomes

A

Loss of one arm of a chromosome and a duplication of the other arm

Lethal in an autosome

FTM2 (10 decks)

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