Question

Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote.I. Viable normal, or translocation carrierII. Viable, with Down syndromeIII. Inviablea. two normal copies of 21, two normal copies of 14b. one 21 to 14 translocation, two normal copies of 21, one normal copy of 14c. one normal copy of 21, two normal copies of 14d. one normal copy of 14, one normal copy of 21, one 21 to 14 translocatione. one normal copy of 14, two normal copies of 21f. two normal copies of 14, one normal copy of 21, one 21 to 14 translocation

Answer 1

The familial down disorder is like an essential down disorder in that it is brought about by trisomy 21. anyway in familial down disorder all or part of the third duplicate of chromosome no 21 has trans situated on to another auto-some regularly chromosome no 14. if there should be an occurrence of the familial down disorder. one of the parent of the influenced kid is regularly a bearer of the trans-found chromosome. the translocation carrier parent don,t have in light of the fact that the individual in question has an aggregate of two duplicates of chromosome no. 21

Viable normal or translocation carrier:- it includes two normal copies of 21 and two normal copies of 14 .

Further, include two normal copies of 21...one will be 21 to 14 and is considered as translocation. It also contains one normal copy of 14

Viable with down syndrome:- it contains one 21 to 14 translocation and one normal copy of 21 and 14

Invisible:- it includes two normal copies of 21 and one normal copy of 14 chromosome

One normal copy of 21 and two normal copies of 14

Two normal copies of 14 and one normal copy of 21 and 14 translocation.

Answer 2

a. two normal copies of 21, two normal copies of 14 – I (normal)

b. one 21 to 14 translocation, two normal copies of 21, one normal copy of 14 - II

c. one normal copy of 21, two normal copies of 14 – III This is monosomy 21 which is lethal*.

d. one normal copy of 14, one normal copy of 21, one 21 to 14 translocation – I This is called balanced translocation (translocation carrier)

e. one normal copy of 14, two normal copies of 21- III This is monosomy 14 which is lethal.

f. two normal copies of 14, one normal copy of 21, one 21 to 14 translocation – III This is trisomy of chromosome 14 and it is lethal.

* lethal leads to spontaneous abortion.