# DBT JRF 2020 — Question 135

Exam: DBT JRF 2020 · Section: B · Topic: Genetics · Difficulty: Easy

## Question

Only 10% of babies with Edward syndrome survive beyond 5 years. This is a genetic disease arising due to

## Options

- **A.** absence of chromosome Y
- **B.** Trisomy 18
- **C.** absence of chromosome 18
- **D.** Trisomy 13

## Answer

Option B

## Explanation

Edward syndrome (Trisomy 18): caused by the presence of THREE copies of chromosome 18 (Trisomy 18) instead of the normal two. Aetiology: non-disjunction during maternal meiosis (usually meiosis II) resulting in an egg with two copies of chromosome 18; most cases (~94%) are full trisomy; ~5% mosaic; ~1% translocations. Clinical features: severe intellectual disability, heart defects (VSD, ASD), micrognathia, rocker-bottom feet, overlapping fingers, omphalocele, growth restriction. Prognosis: ~50% mortality within first week; only ~10% survive beyond 5 years (as stated). More common in advanced maternal age (AMA). Incidence: ~1/3000–5000 live births. Second most common viable autosomal trisomy after Down syndrome (Trisomy 21). Trisomy 13 = Patau syndrome.

Source: https://mypyqbuddy.com/questions/only-10-of-babies-with-edward-syndrome-survive-6a05a8a02adafec47029329f