Genetics...Q 4 - psychmledr

[ArchivalUser]

A baby is born with the clinical characteristics of trisomy 21. C-banding is used to examine the chromosomes of the baby. The father has a C-banding polymorphism that distinguishes both his chromosome 21's from each other and the mother's chromosome 21s as well. The mother's chromosome 21s cannot be distinguished by this banding technique. When the baby's chromosome 21s are examined in metaphase spreads, three uniquely banded chromosomes are identified. This data indicates that the non-disjunction event occurred most likely in which ONE of the following?

A. Paternal meiosis I
B. Maternal meiosis I
C. Meiosis II of either parent
D. During mitosis during early embryogenesis
E. Cannot be determined from the data given


Please answer and EXPLAIN. Thank you

[ArchivalUser]

BB???

[ArchivalUser]

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[ArchivalUser]

the banding would give rise to two different paternal chromosomes... they would also b different from the mothers, so if u got both of the homologus paternal 21 chromosomes, u would get 2 chromosomes that can b distinguished from each other, plus they could b distinguished from the mother's.. so u have 3 uniquely banded chromosomes..
aaaaaaaaaaaaaaaa...

[ArchivalUser]

agree aa as explained by er12 ;thanks mledr good q

[ArchivalUser]

didnt get it....


it says it can be distinguised from each other and not the mothers...

[ArchivalUser]

the 2 paternal chromosomes r different from each other and from the maternal chromosomes , the maternal chromosomes r the same as each others , since the baby has three different chromosomes the only explanation is that he got both of his father"s and one of his mother's. for that to happen non disjunction has to have happened during meiosis 1 in the dad bcuz thats when the 2 homologous chromosomes separate (without breaking the centeomere) . remember that during meiosis 2 each chromosome breaks into 2 chromatids with breaking of the centromere

[ArchivalUser]

Thank you all. And you all are very welcome.

The explanation I have is similar to what moka and er12 wrote, so their explanation will do.

My question is like Paprika’s. What does the statement regarding the mother’s chromosomes
mean?
Of course, we can tell the answer simply from the way the question is worded, but I thought that statement about the mother’s chromososmes was not clear….not to me
Can anyone shed some light there? Maybe I'm missing something here...

Happy studying!!

[ArchivalUser]

"The mother's chromosome 21s cannot be distinguished by this banding technique."

Shouldn't the technique help visualize chromosomes of each person being tested?