Chromosomal Disorder

Question 1

Solenoid meaning ?

Answer 1

Packaging of DNA = 5 nucleosome

Question 2

Type of arm in chromatids?

Answer 2

P=short arm petite

q= long arm grande

Question 3

Morphologically Classified of chromosome ?

Answer 3

Depending on position of centromere

✓ Metacentric – centromere near the middle

3, 16, 19, 20

✓ Acrocentric – centromere near one end

13, 14, 15, 21, 22

✓ Submetacentric – centromere between the
middle and end of

Question 4

In which type of chromosome we can find telomeres ?

Answer 4

Submetacentric

Acrocentric

Question 5

In which type of chromosome we can find satellites?

Answer 5

Acrocentric

Question 6

Which phase is accurate to take karyotype ?

Answer 6

Metaphase

Question 7

What the Karyotype described?

Answer 7

Total number of chromosomes
• Sex chromosome makeup
• Description of any observed abnormality

Question 8

What is the total number of chromosome in
(female Down syndrome)
(cri du chat syndrome)

Answer 8

47,XX,+21 – female down syndrome

46,xx,del(5p) – female with a deletion of the short arm of
chromosome 5 (cri du chat syndrome)

Question 9

From where we can make Chromos Chromosome Analysis

Answer 9

Any tissue with living nucleated cells that undergo
division can be used.
• Lymphocytes from peripheral blood conveniently
used.

amniotic fluid,
✓ chorionic villi,
✓ bone marrow e

Question 10

Way of Preparation of a Karyotype

..?

Answer 10

1- 5 ml venous blood 
2-phytohemagglutinin 
3- culture 37 for 3 days 
4 colchicine +hypotonic saline 
5- cells fixed 
6- spread cells on solids  ..........dropping 
7 digest with trypsin 
8- staining giemsa 
9- metaphase spread 
10 karyotype

Question 11

Light banding in chromosome indicate what

Answer 11

Most of active gene

Question 12

Type of Y chromosome from morphological?

Answer 12

Sunmetacentri

Question 13

Definition of Ideogram?

Answer 13

standardised numbering

system is used for the bands seen in g-banding

Question 14

Type of Chromosome Abnormalities

.

Answer 14

Numerical

✓ Structural

Question 15

Type of Numerical Abnormalities

Answer 15

Aneuploidy

Loss or gain of one or more chromosomes 
✓ Monosomy - loss of a single chromosome, usually lethal
before term  e.g. 45,xx,-21; 45,x 
✓ Trisomy - gain of a single chromosome 
✓ Tetrasomy – gain of 2 chromosomes

Polyploidy
Multiple of haploid number >2n in cells e.G.
69,xxx

Question 16

The cause of Aneuploidy?

Answer 16

non-disjunction

during first or second meiotic
divisions or during mitosis

Question 17

Example of monosomy in meiosis

Answer 17

Lack of an X or a Y chromosome will result in:

45,X karyotype (Turner syndrome)

Question 18

Example of Autosomal Aneuploidy

.?

Answer 18

Edwards syndrome – tri18 Patau syndrome – tri13

Down syndrome – tri21

Question 19

Least sever disorder of trisomy ?

Answer 19

Down Syndrome

Question 20

Types of Down syndrome ?

Answer 20

✓ 95% - complete trisomy
✓ 1% - mosaicism
✓ 4% - unbalanced chromosome rearrangements

Question 21

Type of polyploidy?

Answer 21

egg by two sperm
egg by diploid sperm
diploid egg
Not viable

Question 22

Most common polyploidy is ?

Answer 22

Triploidy

Question 23

Type structural chromosome abnormality?

Answer 23

• Translocations
• Deletions
• Insertions
• Inversions

Question 24

Compare between balanced and unbalanced Rearrangement??

Answer 24

Balanced :
No net loss or gain of chromosomal material
harmless except if it is in an important gene
risk of producing offspring with an unbalanced
chromosome complement
Unbalanced :
Net loss or gain of chromosomal material
Clinical effects usually severe

Question 25

Breaks in more than one chromosome can result in ?

Answer 25

1) Robertsonian translocation Unbalanced
2) Reciprocal translocation balanced
3) Insertional translocation.

Question 26

What happen in Robertsonian Translocations ? Example ?

Answer 26

The short arms of two acrocentric chromosomes are
lost and the long arms fuse at the centromere

14 – 21 translocation is one of the more common abnormalities and may lead to trisomy 21 Causes 5% of Down syndrome

Question 27

The final out come of Reciprocal Translocation

?

Answer 27

Pachytene quadrivalent in meiosis