Structural Change in Chromosome: Whats it reflection behaviour and pattern Course Title: Cytology and Cytogenetics Course Code: BGE357 Structural Change in Chromosome: Whats it reflection behaviour and pattern Course Title: Cytology and Cytogenetics Course Code: BGE357 Group:06 Student ID:49-56 Bangabandhu Sheikh Mujibur Rahman Science & Technology University, Gopalganj-8100 PRESENTATION ON

Structural change of chromosome Chromosomes are the vehicle of hereditary material or genes. Any alteration, addition or deletion of chromosomal part leads to alteration of number, position or sequence of genes in the chromosome. Chromosomes can be structurally identified by their sizes, positions of centromeres and nucleolar organizers, and patterns of chromomeres, heterochromatin, and bands. There are four types of change in the chromosomal structure such as: A.Duplication B.Deletion C.Inversion D.Translocation Structural changes of chromosomes Changes involving in the number of genes DuplicationDeletion Changes involving in the arrangement of genes InversionTranslocation

A. Duplication  Chromosome duplication is a mutation in which part of the chromosome has been duplicated i.e doubled.  A chromosome with segments AB*CDEFG, in which * represents the centromere. After duplication of EF segments it give rise to new segments AB*CDEFEFG  If the duplicated region locate immediately after original segment it is called tandem duplication & if it is located some distance from the original segment it is called displaced duplication. Effect of Duplication: Duplication arise from unequal crossing over. Color blindness is result from unequal crossing over in which one chromosome with an extra opsin gene and another is missing an opsin gene. Duplication of EF segment

B. Deletion  Deletion is a chromosome rearrangement in which a segment of chromosome is loss.  A chromosome with segments AB*CDEFG that undergoes a deletion of segment EF would generate the chromosome AB*CDG. Effect Of Deletion:  The phenotypic Consequence of deletion depend on which gene are located in the deleted region.  Many deletion are lethal in the homozygous state because all copies of any essential genes located in the deleted region are missing.  If the deletion include the centromere, the chromosome will not segregate in cell division.

C. Inversion  It is a chromosome rearrangement in which a chromosome segment is inverted-turned 180°.  If a chromosome with segments AB*CDEFG, then chromosome AB*CFEDG represents an inversion that includes segments DEF. Inversion may be of two types. Effect of Inversion:  An Inversion may break a gene into two parts, with one parts moving to a new location &destroying the function of that gene.  If the position of a gene is altered by an inversión, they may be expressed at inappropriate times or in inappropriate tissues.

D. Translocation  A translocation entails the movement of genetic material between nonhomologous chromosome or within the same chromosome.  Translocation should not be confused with crossing over, in which there is an exchange of genetic material between homologous chromosomes. It may be of two types. Effect of Translocation:  They may create new linkage relations that affect gene expression.  In Robertsonian translocation the long arm of two acrocentric chromosome become joined to a common centromere through a translocation, generating a metacentric chromosome with two long arm & another with two very short arm which fails to segregate & causes down syndrome.

Would anyone like to ask questions ?