CHROMOSOMAL ABBREVATIONS S.Y.BSc SEMESTER III BOTANY PRACTICAL CHROMOSOMAL ABBREVATIONS BY DEPARTEMENT OF BOTANY SATISH PRADHAN DNYANASADHANA COLLEGE, THANE (w)

Chromosomal Aberrations

Karyotype is the entire chromosome complement of the cell. In human there are 23 pairs of chromosomes of which 22 chromosomes are autosomes and one pair is of sex chromosomes. The sex chromosomes are X and Y. In human beings autosomal chromosomes are present in two identical copies i.e. diploid (2n). Haploid (n) cells have a single copy. The chromosomes are arranged and displayed in its standard format known as idiogram. The arrangement is according to the size of the chromosomes and position of the centromere.

Chromosomal Aberration It is of two types: Structural aberrations may be deletion (Cri-du-chat), duplication, inversion or translocation (Philadelphia chromosome).   Numerical aberrations are either aneuploidy i.e. gain or loss of one or more chromosome( Down’s Syndrome; trisomy of chromosome 21) or euploidy i.e. gain or loss of set/s of chromosome/s.

I) Cri – du – chat syndrome:- - It is also known as Chromosome 5p deletion syndrome, 5p – (said minus) syndrome or Lejeune’s syndrome. It is a rare genetic disorder due to a missing part (deletion) of the end of the short (p) arm of the Chromosome 5. It is a type of structural abnormalities in human beings. Its name is a French term referring to the characteristic cat like cry of affected children. Occurs 1 in 50,000 live births. SYMPTOMS The cry of the affected child is similar to that of a meowing kitten, due to problems with the larynx and nervous system. Difficulty in food swallowing and sucking. Low birth weight and poor growth. Small head and jaw, wide eyes. The affected child have difficulties in communication. Affected females develop secondary sexual characters and menstrual cycle. Affected males are with small testes but with normal spermatogenesis DIAGNOSIS & MANAGEMENT : Genetic counselling and genetic testing may be offered to families of affected individuals. Amniocentesis can help in detection of disorder. Children may be treated by speech, physical and occupational therapists.

II) Philadelphia Chromosome :- (Ph chromosome) Philadelphia Chromosome is also known as Philadelphia Translocation. . SYMPTOMS: It is a type of structural abnormalities in human beings. It is the result of a reciprocal translocation between Chromosome 9 and 22. It is specifically designated as t(9;22)(q34;q11). As a result of translocation, a fusion gene is created by juxtapositioning the ABL1 gene on Chromosome 9 (region q.34) to a part of the BCR (Breakpoint Cluster Region) gene on Chromosome 22 (region q.11). DIAGNOSIS & MANAGEMENT Some chemotherapy with specific drug treatment had been mentioned to have curative potential. Bone marrow transplant is also suggested in many cases.

II) Down’s Syndrome It is also known as Trisomy 21. It is caused by the presence of all or part of a third copy of Chromosome 21. It occurs due to non- disjunction of chromosome pair 21 during meiotic division. It is a type of numerical abnormalities in human beings. It is the most common chromosomal abnormality in humans occurring in about one per 1000 babies born each year. SYMPTOMS:- Affected people have physical and intellectual disabilities. They also have poor immune function. They have slanted eyes Small head, flat nose, tongue protruding. Short in stature, average male height is 5 feet 1 inch while average female height is 4 feet 8 inch. Males are infertile while females have lower rate of fertility. DIAGNOSIS & MANAGEMENT It can be identified during pregnancy by parental screening followed by diagnostic testing, or after birth by direct observation and genetic testing. After the screening & confirmed diagnosis, pregnancies are often terminated . Education and proper care for the affected individual can bring about improved life quality.

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