Cytogenetics

Question 1

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

Answer 1

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

Question 2

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

Answer 2

Barr Bodies

Question 3

What is the utility in finding the Barr body?

Answer 3

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

Question 4

How can we find the Y body? Why?

Answer 4

Brilliant Fluorescence

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

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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

Question 7

Parts of the Chromosome (3 important ones)

Answer 7

p - Short arm
q - Long arm
Centromere

Question 8

What is Karyotyping? Checking for?

Answer 8

Length of Chromosome

Structure of Chromosome

Question 9

Karyogram Vs Karyotype Vs Idiogram

Answer 9

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

Question 10

Grouping of Chromosomes according to arm ratio

Metacentric Chromosome

Answer 10

Centromere in the middle

p=q

Question 11

Grouping of Chromosomes according to arm ratio

Submetcentric Chromosome

Answer 11

p is a bit smaller than q

Question 12

Grouping of Chromosomes according to arm ratio

Acrocentric Chromosome

Answer 12

p is much smaller than q

Question 13

Grouping of Chromosomes according to arm ratio

Telocentric Chromosome

Answer 13

p=0
q»>
(Not found in human)

Question 14

What is the NOR?

Answer 14

Nucleolar organizer region

These are repetitive rDNA - rRNA genes

Question 15

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

Answer 15

Giesma Stain

Question 16

G-Banding - Giesma with SAR attachment -

What will appear dark?

Answer 16

A and T rich regions

Question 17

G-Banding - Giesma with SAR attachment -

What will appear light?

Answer 17

G-C rich regions

Question 18

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

Answer 18

Interphase

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

Question 19

How many regions are in each arm of the chromosome?

Answer 19

2

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

Question 20

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

Answer 20

Band

Question 21

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

Answer 21

Sub-Band

Question 22

What does it mean if a chromosome is qh positive?

Answer 22

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

Question 23

FISH - Initials

Answer 23

Fluorescence In-Situ Hybridization

Question 24

FISH

4 Steps

Answer 24

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

Question 25

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

Answer 25

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

Question 26

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

Answer 26

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

Question 27

Mutagenic Tests - What are they for?

Answer 27

For every drug - Prevention of Carcinogenic effects

Question 28

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

Answer 28

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

Question 29

Howell-Jolly Bodies

Answer 29

Micronuclei in human peripheral blood indicate a ruptured or absent spleen

Question 30

Eupoildy

Answer 30

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

Question 31

Aneupoildy

Answer 31

Not an exact multiple of 23 in genome | 24, 47, 45

Question 32

Down syndrome - Genome structure

Answer 32

47, XX or XY , 21 Trisomy

Question 33

What is the most frequent Trisomy cause of abortion?

Answer 33

16

Question 34

Patau Syndrome - Genome Structure

Answer 34

47, XX or XY, 13 Trisomy

Question 35

Edwards Syndrome - Genome Structure

Answer 35

47, XX or XY, 18 Trisomy

Question 36

Klinefelter Syndrome - Genome structure

Answer 36

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

Question 37

Turner Syndrome - Structure of Genome

Answer 37

45, X, Haploid-Insufficiency

Question 38

Jacobs Syndrome - Genome Structure

Answer 38

47, XYY | Double-Y or Superman Syndrome

Question 39

What is the chromosome number of Tripoidy?

Answer 39

69

Question 40

Paracentric Inversion

Answer 40

From ABCDEF to ABEDCF

Question 41

Interstitial Deletion

Answer 41

ABCDEF to ABDEF

Question 42

Reciprocal Translocation

Answer 42

ABCopq | imnDEF

Question 43

Abbreviation of Paracentric in version in chromosome 9? | What is the common consequence of this?

Answer 43

inv(9) | Miscarriage

Question 44

What is the abbreviation of Duplication in chromosome 7?

Answer 44

Dup(7)(q11q22)

Question 45

Abbreviation of Deletion in Chromosome 1?

Answer 45

Del(1)(q24q21)

Question 46

William Syndrome

Answer 46

Caused by Microdeletion in Chromosome 7. | Excessive Happiness and Moved by music.

Question 47

What is the Genome structure of Cri-Du-Chat syndrome? | This is an example for -

Answer 47

46, XX, Del(5)(p15.3p14) | Terminal Deletion

Question 48

Example for Balanced reciprocal translocation -

Answer 48

7-22 (q/p) | Could be causing miscarriage and Infertility

Question 49

Unbalanced Translocation - example ?

Answer 49

7-21 (7,7,7q/21p,21) | Monsomy of Chromosome 21

Question 50

Reciprocal translocation that results in Philadelphia Chromosome

Answer 50

Balanced translocation- t(9,22)(q34,q11) | BCR-ABL1 fusion gene formed is a Tyrosine kinase that leads to CML!

Question 51

What is the cause of Burkitt Lymphoma?

Answer 51

Balanced Translocation induced by Epstein-Bar Virus. | C-myc related (8q24), could be t(8,14)/t(8,2)/t(8,22)

Question 52

What are the five acrocentric Chromosomes? | What important gene is in their p are?

Answer 52

13, 14, 15, 21, 22 | NOR (10x for rRNA)

Question 53

Robertosonian Translocation

Answer 53

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

Question 54

45, XX, t(13,14) fusion

Answer 54

Robertonion Translocation

Question 55

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

Answer 55

Patau Syndrome with Robertosonian Translocation

Question 56

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

Answer 56

Down Syndrome with Robertsonian Translocation

Question 57

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

Answer 57

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

Question 58

Isochromosome

Answer 58

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

Question 59

Dicenritc Chromosome

Answer 59

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

Question 60

Why is chromosome 2 so long?

Answer 60

Dicentric Chromosome originated from Chimps

Question 61

Prader-Willi syndrome | Genome Structure

Answer 61

46, XY, del(15q11-q13)