Lab 4 2022 Chromosomal Aberrations PDF

Lab. 4 Chromosomal aberrations  Chromosomal aberrations Classified as : Numerical chromosomal aberrations Structural chromosomal aberrations  Numerical aberrations Euploidy Aneuploidy increase in the number of...

Lab. 4 Chromosomal aberrations  Chromosomal aberrations Classified as : Numerical chromosomal aberrations Structural chromosomal aberrations  Numerical aberrations Euploidy Aneuploidy increase in the number of variation in the number of a particular complete set of chromosomes chromosome within a set. occurs frequently in plants, rarely in animals. Hypoploid Hyperploid Examples: Haploid (n) Decrease in the Increase in the “Normal in human gametes” number of number of chromosomes chromosomes within a set. within a set. Diploid (2n) “Normal in human somatic cells” Example: Examples: Monosomy (2n-1) Trisomy (2n+1) Polyploid “Possessing more than two Tetrasomy (2n+2) complete sets of chromosomes (triploid (3n), tetraploid (4n), …)” Double trisomy (2n+1+1)  Notes ✔ Ploid is the number of complete set of chromosomes in a cell. ✔ The prefix (eu-) means well or true. ✔ The prefix (an-) means not or without. ✔ The prefix (hypo-) means under or decrease. ✔ The prefix (hyper-) means over or increase.  Polyploidy Normal Polyploidy Polyploidy  Polyploidy Triploid in human Tetraploid in human  Polyploidy Polyploidy in rat Polyploidy in mice  Endomitosis Endomitosis is the replication of DNA in the absence of cell or nuclear division, resulting in numerous copies of DNA within each chromosome. It is also referred to as endoreduplication which result in the replication of the nuclear genome in the absence of mitosis, which leads to polyploidy. Polyploidy Endomitosis (4n) (4n) 92 chromosomes, 46 chromosomes, Each chromosome have Each chromosome have 2 one copy of DNA molecule copies of DNA molecule  Endomitosis Endomitosis Endomitosis in mice Monosomy Monosomy Example on monosomy aberration in human?  Monosomy Monosomy (39 chromosomes) in mice.  Hyperploidy Trisomy (2n+1) Tetrasomy (2n+2) Double trisomy (2n+1+1) Hyperploidy  Hyperploidy Hyperploidy (42 chromosomes) in mice [tetrasomy or double trisomy].  Structural aberrations 1. Chromatid gap 2. Chromatid break 3. Terminal deletion 4. Dicentric chromosome 5. Ring chromosome 6. End to end association 7. Centric fusion 8. Centromeric attenuation 9. Triradial and Quadriradial configurations 10. Pulverization  Chromatid gap Chromatid discontinuity with a length less than the width of the chromatid. Chromatid gap Chromatid gap Chromatid gap in mice  Chromatid break Chromatid discontinuity with a length more than the width of the chromatid. Chromatid break  Chromatid break 1 Chromatid break in rat Chromatid breaks in human  Terminal deletion A deletion that occurs towards the end of a chromosome. Deficiency in the length of one chromatid with OR without the presence of the deleted acentric fragment. Terminal deletion Terminal deletion Terminal deletion  Dicentric chromosome Chromosome with two centromeres result from the fusion of two chromosome pieces, each of which includes a centromere. Dicentric chromosome Breaks in chromatids of 2 chromosomes and formation of sticky ends Telomere Fusion between sticky ends of 2 chromosomes Dicentric chromosome Dicentric chromosome  Dicentric chromosome Dicentric chromosome in human Dicentric chromosome in human. AF: Acentric fragment; DC: Dicentric chromosome  Ring chromosome Fusion of the two ends of the sister chromatids of one chromosome. Ring chromosome  Ring chromosome Ring chromosome in mice  End to end association Fusion of the two ends of two non-sister chromatids of two chromosomes. Telomere Breaks in one chromatid in each of Fusion between the two chromosomes and sticky ends of 2 formation of sticky ends chromosomes End to end association End to end association End to end association in rat. Centric fusion (Robertsonian translocation) Break in the short arm of one acrocentric chromosome and the long arm of another acrocentric chromosome resulting in the formation of one large metacentric chromosome and a minute chromosome (Fragment). Centric fusion Karyotype of a patient with Robertsonian translocation: 45, XY, der (13;14) (q10;q10).  Centric fusion Centric fusion in rat. Centric fusion in mice.  Triradial and Quadriradial configurations Fusion among three or four chromosomes which give rise to tri- or quadri- radial configurations, respectively. Telomere Breaks in chromatids of 3 chromosomes and formation of sticky ends. Fusion between sticky ends of 3 chromosomes Triradial configuration  Telomere Breaks in chromatids of 4 chromosomes and formation of sticky ends. Fusion between sticky ends of 4 chromosomes. Quadriradial configuration Triradial and Quadriradial configurations Quadriradial configurations Quadriradial configurations  Centromeric attenuation Separation between the sister chromatids of at least 3 chromosomes of a cell. It may indicate degeneration of the kinetochore (a protein sheath that bind the two sister chromatids together and mediates the bipolar attachment of sister chromatids to spindle microtubules during cell division). Centromeric attenuation Centromeric attenuation Centromeric attenuation  Pulverization The chromosomes are reduced to masses of very small and occasionally fragments. Individual chromosomes are seldom recognized. Such unconventional aberration is often noted after certain viral infections. Pulverizations Pulverizations Pulverizations  Polyploidy Centromeric attenuation Endomitosis