The first two generations of the Smith family, shown below, are healthy, so they

Question

The first two generations of the Smith family, shown below, are healthy, so they are surprised when Laura and her husband Aaron, and Dylan and his wife Iris, have children, that show symptoms of a genetic disorder. Karen, Leslie, and Lance have a rare condition called DiGeorge syndrome. The children have small facial features and low, rotated ears. More serious symptoms are defects in the blood vessels leading from the heart, impaired immunity, and disturbed calcium metabolism. 1 Dylan and Iris consult a genetic counselor, Ms. Reese, who is concerned that their niece Karen has the same syndrome as Leslie and Lance. She learns that Iris has had several spontaneous abortions, as has her sister-in- law, Laura. Noting the combination of repeated birth defects and pregnancy losses, Ms. Reese suggests that Dylan and Laura and their siblings, children, and parents be karyotyped. The results, unfortunately confirm the genetic consoler's suspicions. Perry, Holly, Ariel, Sherri, and Shane have normal chromosomes. Laura, Dylan, Zach and Kim have a balanced reciprocal translocation between chromosomes 20 and 22. They have no symptoms, but are translocation carriers with the following chromosomes. 9 Perry Brenda Dylan Ins Holly Karen Sherri Shane Leslie Lance Kim Translocation Normal 22 Excess 22 Deficient 20 Translocation Excess 20 Normal 20 Deficient 22

Explanation / Answer

Please find the answers below:

Answer 1: Choice A (Since these three kids are normal physiologically, they must have normal genotype. Another set of condition would be the one in which the were heterozygous in nature but that doesn't hold true since an acrocentric chromosome cannot undergo translocation or reciprocation)

Answer 2: Choice C (trisomy of chromosome 20 is deleterious genetically causing adverse effects. However, monosomy is even more deleterious as it causes serious genetic problems including destabilization of the zygote, hence causing spontaneous abortions)

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