Question

A child with Down Syndrome is born to a normal couple who have no prior history of the disease. Illustrate with a diagram how it would occur during gametogenesis. What factors would influence the birth defects of an individual with Down Syndrome?

Answer 1

Ans. Down Syndrome - this disease was ist described by Langdon Down in 1866.It is autosomal linked recessive diseases occur due to trisomy of 21st chromosome. Such condition of trisomy appear due to formation of abnormal male and female gametes as a result of non-disjunction .

Factors influencing birth defects of an individual with Down syndrome-

• Advancing maternal age. A woman's chances of giving birth to a child with Down syndrome increase with age because older eggs have a greater risk of improper chromosome division. A woman's risk of conceiving a child with Down syndrome increases after 35 years of age.
• Being carriers of the genetic translocation for Down syndrome. Both men and women can pass the genetic translocation for Down syndrome on to their children.
• Having had one child with Down syndrome. Parents who have one child with Down syndrome and parents who have a translocation themselves are at an increased risk of having another child with Down syndrome. A genetic counselor can help parents assess the risk of having a second child with Down syndrome.