1. Practical 7 Numerical chromosomal abnormalities – conclusion

2. Nondisjunction of sex chromosomes during spermatogenesis – 1 st meiotic division XY XY XY XY XXY XXY X X +X nondisjunction fertilization

3. Nondisjunction of sex chromosomes during spermatogenesis – 2 nd meiotic division – X chromosome XY Y X XX Y Y XXX X XY XY +X nondisjunction fertilization

4. Nondisjunction of sex chromosomes during spermatogenesis – 2 nd meiotic division – Y chromosome XY Y X X X YY XX XX XYY X +X nondisjunction fertilization

7. Practical 7 Structural chromosomal abnormalities

8. Task 2 : The photo 1 shows multiple structural abnormalities after irradiation of an individual with high dosage of X-rays. Describe structural chromosomal aberrations on the photo. Photo 1 gap breakage triradial quadriradial chromatid breakage chromosomal (double-chromatid) breakage

11. Terminal deletion of short arms of the chromosome 5 46,XY,del(5)(p15.2) Simplified finding: 46,XY,del(5p)

14. Robertsonic translocation of chromosomes 14 and 21 Down syndrome – translocation form der(14;21)

15. Robertsonic translocation = robertsonic fusion = centric fusion Translocation of two acrocentric chromosomes, centromeric fusion. derivative chromosome

16. 46,XY,der(14;21)(q10;q10),+21 older description : 46,XY,t(14;21)

17. For calculation of the risk for further offspring karyotyping of parents is necessary.

18. Karyotype of the mother balanced robertsonic translocation of chromosomes 14 and 21 Photo – karyotype 5

19. 45,XX,der(14;21)(q10;q10) older description: 45,XX,t(14;21)

20. The mother is carrier of balanced robertsonic translocation of chromosomes 14 and 21. She is healthy but her offspring has increased risk of the Down syndrome.

21. Risk for further offspring Normal karyotype Carrier M. Down Trisomy 14 Monosomy 21 Monosomy 14 Lethal during prenatal development Theoretical risk 1/3 … 33% Empiric risk 8 – 10% Chromosomal constitution of mother carrier:

23. Robersonic translocation of two 21 chromosomes Translocation form of the Down syndrome der(21;21)

24. 46,XY,der(21;21)(q10;q10),+21 older description : 46,XY,t(21;21) der(21;21)

25. Karyotype of the mother balanced robertsonic translocation of two 21 chromosomes Photo (karyotype) 7 der(21;21)

26. 45,XX,der(21;21)(q10;q10) older description: 45,XX,t(21;21) der(21;21)

27. Risk for further offspring der(21;21) Risk: 100% +21 fertilization der(21;21) nulisomic gamete m. Down monosomy 21 – lethal during early prenatal development

28. Task 6 A girl with a Turner syndrome features had been examined in the genetic counselling clinic. Describe her karyotype and determine the chromosomal finding.

29. Isochromosome of long arm of chromosome X 46,X,i(X)(q10) older description: 46,X,iso(Xq)

30. Origin of isochromosomes i(Xp) i(Xq) Normal separation in anaphase Abnormal division – origin of i s ochromosomes Xp and Xq

32. Origin of ring chromosome reparation deletion of terminal segments ring chromosome r(X)

36. See you at the end of the summer term!