chromosmal aberrations
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For the animal genetics courseTRANSCRIPT
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
3Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Karyotype of Goat
4Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Karyotype of Sheep 54 XY & 54 XX
Ram
Ewe
5Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Karyotype of Buffalo 50 XX and 50XY
6Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Swine chromosomes, 2n=38,XX
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Karyotype of Dog
8Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Cat chromosomes, 2n=38,XX.
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Karyotype of Horse 64 XY
10Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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
11Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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
13Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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.
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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Reciprocal Translocation
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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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.
Dr 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 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
17Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Chromosomal AberrationsStructural abnormalities
18Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
Induced by Radiation
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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 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
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Numerical Aberration
30Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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Polyploidy -Numerical abnormality
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Triploidy
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Monosomic
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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
35Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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
36Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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
37Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
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.
38Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore