chromosmal aberrations

Chromosomal Aberrations

AGB 121

Dept. of AGB

Veterinary College, Hebbal, Bangalore

Normal Structure of chromosome

2Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

Normal Karyotype of domestic animals

Catt le chromosomes, 2n=60, XY. S ta in metho d B rdU inco rporat ion - Acr id ineOrange


Karyotype of Goat


Karyotype of Sheep 54 XY & 54 XX

Ram

Ewe


Karyotype of Buffalo 50 XX and 50XY


Swine chromosomes, 2n=38,XX


Karyotype of Dog


Cat chromosomes, 2n=38,XX.


Karyotype of Horse 64 XY


Autosomal pair Sex chromosome

Diploid No. of No. of X Y

(2n) metacentrics acrocentric or telocentric

Cat 38 16 2 M M

Dog 78 0 38 M A

Pig 38 12 6 M M

Goat 60 0 29 A M

Sheep 54 3 23 A M

Cow 60 0 29 M M

Horse 64 13 18 M A

M – Metacentric; A – Acrocentric


Chromosomal aberrations

Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Structural Numerical

Euploidy Aneuploidy

1. Translocation

2. Inversions

3.Duplication/

Additions

4. Deletions

1. Monoploidy

2. Triploid

3. Tetraploid

i. Autotetraploid

ii. Allotetraploid

4. Polyploid

1. Monosomic

2. Trisomic

3. Tetrasomic

4. Double trisomic

5. Nullosomic


Structural aberrations

Structural Aberrations

• Translocation: Broken ends of two chromosomes rejoin into non-homologous portions of chromosomes.

1. Simple translocation: A piece of one chromosome goes and attaches to another chromosome.

2. Reciprocal Translocation: Involves the exchange of segments between two non-homologous chromosomes.


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Reciprocal Translocation


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Homozygous reciprocal translocation

A B C D E F C D

A B C D E F C D

E F G H A B G H

E F G H A B G H

Both the homologous chromosome exchange parts with two

homologous chromosome of another pair.


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•Heterozygous reciprocal translocation

If only one member of each of the two homologous pair

exchange the parts.

A B C D E F C D

A B C D A B C D

E F G H A B G H

E F G H E F G H

DuplicationThe presence of an additional chromosome

segment, as compared to that normally present in a nucleus is known as Duplication.

• Four types of duplication:

1. Tandem duplication

2. Reverse tandem duplication

3. Displaced duplication

4. Translocation duplication


Chromosomal AberrationsStructural abnormalities


Induced by Radiation


Chromosome conservation

Studies based on :

1. Constant autosomal arm number (NAA) ranging from 30-60.

2. Chromosomal mutation- Centric fusion.

3. Similarity in the chromosome arms noticed based on various banding techniques.

Comparison of Chromosomes of Livestock

• Cattle & Goat have 60 pairs and Sheep has 54 pairs. • All autosomes are acrocentric in Cattle and Goats.

The X-chromosome Goat - acrocentric Cattle's -X sub-metacentric)

Y ChromosomeSmallerLarger

In sheep the same differences in the sex-chromosomes are found, but in addition there are three centromere fusions of autosomes.

The chromosomes, 1/3, 2/8 and 5/11, are fused in comparison with those in cattle and goat. Therefore, the sheep has only 54 chromosomes.

Chromosomes of Buffaloes50,XX or 50XY

Based on banding the chromosome 1 to 5 in buffaloes has been formed by centric fusion of ten acrocentric autosomes of cattle:

1 and 27, 2 and 23, 8 and 19, 5 and 28 and 16 and 29, respectively.

Comparison of River and Swamp Buffalo

• Riverine Buffalo-2n=50 Chromosome 4 &9 are separate.

• Swamp Buffalo-2n=48 Chromosome 4 & 9 appear as enlarged pair due to chromosome translocation.

• Crossbreds -2n=49 due to the 4/9 tandem fusion

• F2’s may have 2n as 48,49 and 50.

• Beyond 75% inheritance 2n=50

X chromosome homology

Cattle- Submetacentric

River Buffalo -Acrocentric

Sheep-Acrocentric with small visible ‘p’ armBands are conserved except that in Buffaloes the centromere is repositioned with loss of constitutive heterochromatin.Comparison of Bovine with Caprine -four chromosome transposition including centromere repositioning

Y chromosome homology

Bos taurus -Submetacentric

Bos indicus -Acrocentric with small visible pericentric inversion

Buffaloes-It larger than Bos taurus of because of addition of heterochromatic region

Robertsonian Translocation


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Translocation

Ring chromosome

Dr R Jayashree, Asst. Prof(AGB) Veterinary College, Bangalore

Numerical Aberration



Polyploidy -Numerical abnormality


Triploidy


Monosomic


Klinefelter syndrome

Freemartin• Infertile female when born as a co-twin to a

male calf

• The calf will have masculanized behaviour and non functioning ovaries


Karyotype of freemartin

It is Chimeric with the sample of cells showing XX/XY chromosomes. and pigs

Externally, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-Müllerianhormone from the male twin.

It also occurs occasionally in other mammals including sheep, goats and pigs


Freemartinism

The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas


Cri-du-chat (Cat cry syndrome):

The name of the syndrome came from a cat like mewing cry from small weak infants with the disorder.

Other characteristics are microcephaly (small head), broad face and saddle nose, physical and mental retardation.

Cri-du-chat patients die in infancy or early childhood.

The chromosome deficiency is in the short arm of chromosome 5 .

Myelocytic leukemia

A deletion of chromosome 22 was described by P.C.Nowelland Hungerford and was called “Philadelphia” (Ph’)chromosome after the city in which the discovery was made.


chromosmal aberrations

Documents

xxramewe5dr r jayashree

xy10dr r jayashree

radiation19dr r jayashree

50xy6dr r jayashree

acrocentric11dr r jayashree

xx7dr r jayashree

nullosomic13dr r jayashree

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