Video Transcript
Down syndrome is an example of a syndrome caused by chromosomal abnormalities. Which of the following is not a common trait associated with Down syndrome? (A) Heart defects, (B) intellectual disabilities, (C) delayed development of speech, (D) weak muscle tone, or (E) rapid growth during puberty.
Down syndrome or trisomy 21 is a fairly common disorder caused by chromosomal abnormalities. Let’s learn a little bit more about the syndrome before we answer the question.
Humans generally have 46 chromosomes organized into 23 pairs. The last pair of chromosomes are called the sex chromosomes, and these are the ones responsible for determining the biological sex of the individual. A change in the expected number or structure of these chromosomes can cause chromosomal abnormalities, such as Down syndrome.
People with down syndrome have three copies of the 21st chromosome instead of the usual two. Having three copies of a single chromosome is referred to as a trisomy. As a result, people with Down syndrome have 47 chromosomes in total instead of 46. Having an extra copy of chromosome 21 causes several problems with growth and development. While different people with Down syndrome can have different traits, there are some that are quite commonly observed in people with this condition.
Let’s start by looking at some of the mental traits that people with Down syndrome may have. Children with Down syndrome often have learning disabilities and delayed speech development. Both of these are listed as answer choices in our question. Since we’re looking for a trait that is not associated with Down syndrome, we can rule these answers out.
Physically, people with Down syndrome are often shorter in height, have weaker muscle tone, and congenital heart defects. They may also exhibit characteristic facial features, such as a flattened facial profile and upward slanting eyes. Our answer choices include weak muscle tone and heart defects, so we can rule these options out as well.
Let’s take a look at answer choice (E), rapid growth during puberty. This is not a trait that is associated with Down syndrome. In fact, as we have learned, people with Down syndrome are often shorter in height than other people their age who do not have Down syndrome. Therefore, the correct answer is (E), rapid growth during puberty.
