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Cytogenetics Flashcards

1
Q

What is the X inactivation and what is the resulting pattern?

A

Inactivation of the chromosome X of Paternal or Maternal randomly in different cells in the female offspring. Functional Mosaicism is the resulting pattern.

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2
Q

What is the form retained in granulocytes by the Inactive X?

A

Barr Bodies

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3
Q

What is the utility in finding the Barr body?

A

Checking for chromosomal abrasions and Proof of female sex in an individual.

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4
Q

How can we find the Y body? Why?

A

Brilliant Fluorescence

It is a very condensed one and it has a natural autofluorescence.

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5
Q

What are the direct and Indirect ways to prepare for chromosome detection?

A

Direct - Simply looking for a dividing cell in the smear, not probable
Indirect - In vitro stimulation to get to metaphase and stopping it there.

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6
Q

How can we isolate the chromosomes in metaphase from the cells for microscopic preparation? 3 general steps

A

Centrifugation for concentration and later adding a low salt solution for elimination of cells. Staining with Giesma.

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7
Q

Parts of the Chromosome (3 important ones)

A

p - Short arm
q - Long arm
Centromere

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8
Q

What is Karyotyping? Checking for?

A

Length of Chromosome

Structure of Chromosome

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9
Q

Karyogram Vs Karyotype Vs Idiogram

A

Karyogram - From one cell
Karyotype - From one species
Ideograms - 150 human samples

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10
Q

Grouping of Chromosomes according to arm ratio

Metacentric Chromosome

A

Centromere in the middle

p=q

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11
Q

Grouping of Chromosomes according to arm ratio

Submetcentric Chromosome

A

p is a bit smaller than q

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12
Q

Grouping of Chromosomes according to arm ratio

Acrocentric Chromosome

A

p is much smaller than q

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13
Q

Grouping of Chromosomes according to arm ratio

Telocentric Chromosome

A

p=0
q»>
(Not found in human)

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14
Q

What is the NOR?

A

Nucleolar organizer region

These are repetitive rDNA - rRNA genes

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15
Q

What is the staining used for investigation of Chromosomes? The basic one

A

Giesma Stain

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16
Q

G-Banding - Giesma with SAR attachment -

What will appear dark?

A

A and T rich regions

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17
Q

G-Banding - Giesma with SAR attachment -

What will appear light?

A

G-C rich regions

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18
Q

What is the state of the cell that allows us to check for the Barr bodies?

A

Interphase

No need to special preparation - Barr bodies are large enough to be recognized in granulocytes

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19
Q

How many regions are in each arm of the chromosome?

A

2

Meaning if we get a location of a gene in q13 than 1 will be the region in the long arm

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20
Q

In a gene located in q13. What is the meaning of 3?

A

Band

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21
Q

In a gene located in p11.4. What is the meaning of 4?

A

Sub-Band

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22
Q

What does it mean if a chromosome is qh positive?

A

Excess of centric heterochromatin in the long arm- chromosome polymorphism.

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23
Q

FISH - Initials

A

Fluorescence In-Situ Hybridization

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24
Q

FISH

4 Steps

A

1 - Denaturation
2 - Hybridization with small labeling molecules (per sequence)
3 - Fluorochrome labeled Antibodies bind to the labeling molecules
4 - Epifluorescence Microscopy - Location of gene measured

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25
Q

Which chromosomes are most frequently checked with FISH for Pre-Natal observations? (5)

A

21 - Down Syndrome
18 - Edwards Syndrome
13 - Patau Syndrome
X and Y

26
Q

What are the 3 alternative uses of FISH? (Presented in slides)

A

M- Banding
G-Band
M-FISH - Chromosome Territories

27
Q

Mutagenic Tests - What are they for?

A

For every drug - Prevention of Carcinogenic effects

28
Q

SCE (Sister chromatid exchange) detection of mutagenic agents
What is the agent used?

A

Bromodeoxyuridine - analogue for thymidine
It will degenerate in case of radiation.
It will stain for Giesma (if no radiation).

29
Q

Howell-Jolly Bodies

A

Micronuclei in human peripheral blood indicate a ruptured or absent spleen

30
Q

Eupoildy

A

Exact multiple of 23 in genome
Normally - Haploid (23), Diploid (46)
Abnormal - 69,92… (tri,tetra)

31
Q

Aneupoildy

A

Not an exact multiple of 23 in genome

24, 47, 45

32
Q

Down syndrome - Genome structure

A

47, XX or XY , 21 Trisomy

33
Q

What is the most frequent Trisomy cause of abortion?

34
Q

Patau Syndrome - Genome Structure

A

47, XX or XY, 13 Trisomy

35
Q

Edwards Syndrome - Genome Structure

A

47, XX or XY, 18 Trisomy

36
Q

Klinefelter Syndrome - Genome structure

A

47, XXY (or more Xs, Bar bodies number can range from 1 to 3)

37
Q

Turner Syndrome - Structure of Genome

A

45, X, Haploid-Insufficiency

38
Q

Jacobs Syndrome - Genome Structure

A

47, XYY

Double-Y or Superman Syndrome

39
Q

What is the chromosome number of Tripoidy?

40
Q

Paracentric Inversion

A

From ABCDEF to ABEDCF

41
Q

Interstitial Deletion

A

ABCDEF to ABDEF

42
Q

Reciprocal Translocation

A

ABCopq

imnDEF

43
Q

Abbreviation of Paracentric in version in chromosome 9?

What is the common consequence of this?

A

inv(9)

Miscarriage

44
Q

What is the abbreviation of Duplication in chromosome 7?

A

Dup(7)(q11q22)

45
Q

Abbreviation of Deletion in Chromosome 1?

A

Del(1)(q24q21)

46
Q

William Syndrome

A

Caused by Microdeletion in Chromosome 7.

Excessive Happiness and Moved by music.

47
Q

What is the Genome structure of Cri-Du-Chat syndrome?

This is an example for -

A

46, XX, Del(5)(p15.3p14)

Terminal Deletion

48
Q

Example for Balanced reciprocal translocation -

A

7-22 (q/p)

Could be causing miscarriage and Infertility

49
Q

Unbalanced Translocation - example ?

A

7-21 (7,7,7q/21p,21)

Monsomy of Chromosome 21

50
Q

Reciprocal translocation that results in Philadelphia Chromosome

A

Balanced translocation- t(9,22)(q34,q11)

BCR-ABL1 fusion gene formed is a Tyrosine kinase that leads to CML!

51
Q

What is the cause of Burkitt Lymphoma?

A

Balanced Translocation induced by Epstein-Bar Virus.

C-myc related (8q24), could be t(8,14)/t(8,2)/t(8,22)

52
Q

What are the five acrocentric Chromosomes?

What important gene is in their p are?

A

13, 14, 15, 21, 22

NOR (10x for rRNA)

53
Q

Robertosonian Translocation

A

Happens in Acrosomal Chromosome

If there are 8 or more copies left of NOR they can live a normal life with risk of Infertility or abortion

54
Q

45, XX, t(13,14) fusion

A

Robertonion Translocation

55
Q

46, XY, der(13,14) + 13

A

Patau Syndrome with Robertosonian Translocation

56
Q

46, XY, Der(14,21) +21

A

Down Syndrome with Robertsonian Translocation

57
Q

46, XX, r(14)(p11,2q32)

A

Ring Chromosome - Miscarriage due to pairing and interlocking of rings - impaired cell division.

58
Q

Isochromosome

A

P arms and Q arms of the homologous chromosomes are detaching.
E.g. - I(X)(p10)

59
Q

Dicenritc Chromosome

A

Fusion of two breaks - meaning the chromosome will have two centromeres

60
Q

Why is chromosome 2 so long?

A

Dicentric Chromosome originated from Chimps

61
Q

Prader-Willi syndrome

Genome Structure

A

46, XY, del(15q11-q13)

GBA Genetics (16 decks)

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