Lecture 11,12 and 13 Fred and Mary have a child with Down syndrome. A VNTR mappi

Question

Lecture 11,12 and 13 Fred and Mary have a child with Down syndrome. A VNTR mapping to chromosome 21 was used to identify the chromosomes 21 in Fred, Mary and the child. The child's band patterns reveal whether non-disjunction occurred in spermatogenesis (in the father) or oogenesis (in the mother), and whether it wasa event. 3. Frank Mary A BC D The child's band pattern could have looked like that of A, B, C, or D of the figure below. (Darker bands indicate signals of twice the intensity). For the A. B, C, and D patterns, in which parent did the non-disjunction occur? And was it at meiosis I or meiosis I1?

Explanation / Answer

Before going to the pictures, lets see what is nondisjunction. When the cell division happened, sometimes chromosomes failed to separate. This event known as nondisjunction.

Now, down-syndrome occurs if nondisjunction happened at meiosis I . Due to this event, egg cell will have an extra copy of chromosome 21. After the fertilization, fertilized egg will have 3 chromosome 21 copy, one from father and two from mother.

Now, when we look at the pictures, childs band pattern could be like shown in figure D.

as it contain an intense band (upper) which we can find at the same position as the lower band of mother. The intense band represents twice the amount. Whereras, the lower band showed similarity with the lower band found in father.

Related Questions

Navigate

• Browse (All)
• Browse L
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.