Chromosomal Abnormalities

Question 1

What does problem in meiosis lead to? And what diesease caused by the problem

Answer 1

Non-disjunction: failure of one or more pair of homologous pair or sister .to separate during nuclear division.
Non-disjunction lead to :Down syndrome (trisomy at 21)
: Patau’s syndrome (trisomy at 13)
Edward’s syndrome (trisomy at 18)
:turner’s’ syndrome (present on X chromosome)

Question 2

What is chromosomal abnormalities? What the two types of it? What is the consequence of chromosomal abnormalities.

Answer 2

It is numerical alteration of chromosome in autosome or sex cell or in both . The type is. -numerical chromosomal abnormalities and structural abnormalities.
Consequence are -miscarriage,subfertility
-cancer
Stillbirth/neonatal death

Question 3

How is chromosomal abnormalities detected?
When is the detection done? When it is not done?

Answer 3

It is detected by karyotyping (cytogenetic testing) and fluorescent in situ hybridisation (molecular cytogenetic testing)
It is done if the couple have 2 or more recurrent spontaneous abortion or they are subfertile. It is not done when the child have chromosomal abnormalities because it is due to non-disjunction.

Question 4

What are the types of abnormalities in number of chromosome?

Answer 4

1.aneuploity
2.mosaic ins
3. Polyploidy

Question 5

What is aneuploity ? Types of it?

Answer 5

It is gain or lost of chromosome due to non-disjunction . It is categorised intoautosomal aneuploidy(Down syndrome, patau syndrome,Edward syndrome) and sex chromosome aneuploity (Klinefelter syndrome , turner syndrome)

Question 6

What is mosaicism. Type of it ?

Answer 6

Presence of two or more genetically different cell line due to non-disjunction. It causes mosaic Down syndrome,mosaic turner syndrome, mosaic trisomy)

Question 7

What is polyploidy? Types of it?

Answer 7

Presence of two or more homologous set of chromosome. It include triploidy( 3 set of chromosomes) andtetrapolidy( 4 set of chromosome)
This is in compatible with life

Question 8

Explain about Down syndrome (trisomy 21)

Answer 8

There is 3 chromosomes in 21 . The person with it have flat nasal bridge,round face ,small ears, small mouth,protruding tongue,short neck,brush field spots in iris

Question 9

Patau syndrome

Answer 9

Cause by chromosomal abnormalities in 13. People with it have small head,clenched fist with extra finger, cleft lip and/or palate,malformed ears

Question 10

Edward syndrome

Answer 10

Cause by chromosomal abnormalities in 18 .
Unusually small head, small jaw and mouth,club feet and toes may be webbed or fused, hand clenched into fist, index finger overlap other fingers

Question 11

Turner syndrome

Answer 11

There is only one X Chromosome(45,X)
Characteristics: webbed neck,horseshoe kidney, broad chest with widely spaced nipples, low set ears, cubits valgus, bicuspid valve

Question 12

Klinefelter syndrome t

Answer 12

Cause by chromosomal abnormalities in sex chromosome (47,XXY)
Characteristics: taller than normal,reduced facial hair, feminine fat distribution,small testes, breast development

Question 13

Types of abnormalities in structure.

Answer 13

Deletion,duplication,inversion,isochromosome,ring chromosomes,reciprocal translocation,dice trio chromosome

Question 14

Deletion

Answer 14

A segment of chromosome deleted or missing . It cause cri-du-chat syndrome,Jacobsen syndrome, William syndrome

Question 15

Define :Duplication, inversion,ring,isochromosome ,dicentric .

Answer 15

Duplication: a segment of gene is duplicated resulting in extra genetic material.
Inversion: segment of gene is break and then segment is reinserted in an inverted manner.
Ring: segment of chromosome broken off and form ring with loss/without lost of genetic material.
Isochromosome: mirror images
Copy of chromosome segment
.
Dicentric chromosomes:

Question 16

Translocation. Types of it

Answer 16

Exchange of segment of chromosome with non-homologous chromosome.
Balance chromosome (no gain or loss of chromosome)
Unbalanced (gain or loss of chromosom and clinically symptomatic)
Robertsonian translocation: involved balance transfer of long arm between two Afrocentric chromosomes