Chromosmal aberrations

Chromosomal Aberrations

AGB 121 Dept. of AGB Veterinary College, Hebbal, Bangalore

Normal Structure of chromosome

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

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Normal Karyot ype of domesti c animal s C a tt l e c h ro mo s o me s , 2 n = 6 0 , X Y. S t a i n m et h o d B rd U i n co r p o ra t i o n - A c r i d i n e O ra n g e

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

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Karyotype of Goat

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

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Karyotype of Sheep 54 XY & 54 XX

Ram

Ewe

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

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Karyotype of Buffalo 50 XX and 50XY

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

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Swine chromosomes, 2n=38,XX

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

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Karyotype of Dog

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

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Cat chromosomes, 2n=38, XX.

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

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Karyotype of Horse 64 XY

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

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Autosomal pair

Diploid (2n) Cat 38 Dog 78 Pig 38 Goat 60 Sheep 54 Cow 60 Horse 64

No. of

Sex chromosome

No. of

metacentrics acrocentric or telocentric 16 2 0 38 12 6 0 29 3 23 0 29 13 18

X M M M A A M M

Y M A M M M M A

M – Metacentric; A – Acrocentric Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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Chromosomal aberrations Structural 1. Translocation 2. Inversions 3.Duplication/ Additions 4. Deletions

Numerical Aneuploidy Euploidy 1. Monoploidy

2. Triploid 3. Tetraploid

1. Monosomic 2. Trisomic 3. Tetrasomic 4. Double trisomic 5. Nullosomic

i. Autotetraploid ii. Allotetraploid

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

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Structural aberrations

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

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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 nonhomologous chromosomes.

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

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Reciprocal Translocation Homozygous reciprocal translocation A

B

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D

E

F

C

D

A

B

C

D

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F

C

D

E

F

G

H

A

B

G

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E

F

G

H

A

B

G

H

Both the homologous chromosome exchange parts with two homologous chromosomeDrof another pair.

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

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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

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D

A

B

C

D

E

F

G

H

A

B

G

H

E

F

G

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E

F

G

H

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

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Duplication The 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

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

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Chromosomal Aberrations Structural abnormalities

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

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Induced by Radiation

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

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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 Chromosome Smaller Larger

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 Buffaloes 50,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’ arm Bands 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

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

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Translocation

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

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Ring chromosome

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

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

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Numerical Aberration

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

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Polyploidy -Numerical abnormality

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

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Triploidy

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

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Monosomic

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

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Klinefelter syndrome

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

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Freemartin • Infertile female when born as a co-twin to a male calf • The calf will have masculanized behaviour and non functioning ovaries

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

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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-M端llerian hormone from the male twin.

It also occurs occasionally in other mammals including sheep, goats and pigs Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore

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

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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.Nowell and Hungerford and was called “Philadelphia” (Ph’) chromosome after the city in which the discovery was made.

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

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