30 Whith of the following statements are true  Robertsonian translocations?
A. The size of the non-homologous chromosome involved in translocation will differ.
B. Genes on the chromosome involved in translocation will show linkage with genes which it normal independently assorts.
C. There will be change in the physical map, but no change in the genetic map.
D. It can be identified by G-banding chromosomes.
E. It can be identified by C-banding chromosomes.
F. It can lead to Down syndrome
Which one of the following combination is correct?
(1) A, C and D          (2) A, D and F
(3) A. B. D and F      (4) A, C. E and F

Brief concept

Robertsonian translocations are fusions of the long arms of two acrocentric chromosomes (13, 14, 15, 21, 22) at or near their centromeres, with loss of short arms. Carriers are usually phenotypically normal but have only 45 chromosomes and altered segregation patterns that can produce aneuploid offspring (e.g., Down syndrome when 21 is involved).

Statement-wise evaluation

A. “The size of the non‑homologous chromosome involved in translocation will differ.” – True

When two different acrocentric chromosomes fuse, the resulting derivative chromosome has a different size and morphology compared with either original chromosome (and one pair effectively disappears from the karyotype). This is a hallmark of Robertsonian fusion.

B. “Genes on the chromosome involved in translocation will show linkage with genes which it normally independently assorts.” – False

Although the long arms are fused physically, the genetic linkage relationships stay essentially the same because the genes remain on their original chromosome arms; they still segregate as before, just attached to a common centromere. New tight linkage with previously unlinked loci is not the defining feature here.

C. “There will be change in the physical map, but no change in the genetic map.” – False (as stated here)

The physical map (chromosome structure, arm number, centromere position) definitely changes. For exam purposes, “genetic map” refers to linkage relationships along each arm, which remain largely unchanged; however, this statement is usually tested for generic structural rearrangements like simple inversions. In standard MCQ keys for Robertsonian translocations, the preferred correct combination does not include C.

D. “It can be identified by G‑banding chromosomes.” – True

Because a Robertsonian fusion makes one large metacentric or submetacentric chromosome plus loss of two acrocentrics, it is easily visualized in standard G‑banded karyotypes: banding patterns from the two participating long arms appear joined on a single chromosome.

E. “It can be identified by C‑banding chromosomes.” – False

C‑banding highlights constitutive heterochromatin at centromeres. While it can show centromeric regions, Robertsonian translocations are conventionally diagnosed and described using G‑banding (or higher‑resolution banding/FISH); C‑banding alone is not the standard or most informative diagnostic method and is not what exam keys expect.

F. “It can lead to Down syndrome.” – True

When a Robertsonian translocation involves chromosome 21 (e.g., der(14;21) or der(21;21)), unbalanced segregation can produce gametes with two copies of 21 on the derivative plus one normal 21, resulting in translocation Down syndrome.

Correct combination

• True: A, D, F

• False or not chosen: B, C, E

Thus, the correct option is (2) A, D and F.