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# Down Syndrome is the most common serious birth defect afflicting child

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Senior Manager
Joined: 31 May 2018
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Location: United States
Concentration: Finance, Marketing
Down Syndrome is the most common serious birth defect afflicting child  [#permalink]

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08 Nov 2019, 09:05
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New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 440, Date: 08-Nov-2019
This post is a part of New Project RC Butler 2019. Click here for Details

Down Syndrome is the most common serious birth defect afflicting children born in the United States today. The condition, which affects one in every 600 births, results from the inclusion of an extra 21st chromosome in the genetic fingerprint of an embryo. A typical human possesses 46 chromosomes in 23 matching pairs, but a person with aneuploidy has either one or three copies of a chromosome instead of a pair. In the case of Down Syndrome, when the aneuploidy results in an additional 21st chromosome, the result of this trisomy can be a significantly pronounced.

The characteristics of a person with Down Syndrome include: distinct facial features, short stature, heart defects, susceptibility to respiratory infection, and mental retardation. It is the most common form of mental retardation in humans and those afflicted with the condition typically have a much shorter life expectancy. Additionally, most people with Down Syndrome are sexually underdeveloped and as a group, they are rarely able to procreate. Those who are able to conceive stand a 50% chance of passing the trisomial condition to their offspring.

Among all parents, the incidence of Down Syndrome in offspring correlates with the age of the mother. Women under 30 have a 0.04% chance of bearing a child with Down Syndrome; that percentage increases to 1.25% for mothers in their early thirties and even higher for women over 35.

1. The condition Trisomy 21 is the sole cause of which of the following?

(A) Aneuploidy
(B) Down Syndrome
(C) Mental retardation
(D) Sexual underdevelopment
(E) All of the above

2. If the number of children born with Down Syndrome has increased steadily for the past 10 years, which of the following observations offers the best explanation?

(A) Couples are choosing to have fewer children than their parents.
(B) The incidence of drug abuse in women of childbearing age Nas steadily increased over the same period.
(C) Alarger number of people with Trisomy 21 are attempting “ to have children.
(D) Todays couples tend to wait longer to start families.
(E) There are a growing number of single mothers.

3. People with Down Syndrome are likely to exhibit which of the following:

(A) Inability to copulate
(B) Extended life expectancy
(C) Mental retardation
(D) An absent chromosome pair
(E) Both (a) and (c)

Spoiler: :: OE
QUESTION-1. The correct answer is (b). Trisomy 21 is a specific condition where there are three 21st chromosomes. This condition is named Down Syndrome.
Choice (a) is incorrect because aneuploidy is the general term for an abnormal number of chromosomes. While Trisomy 21 is one type of aneuploidy, there can be others.
Choice (c) is incorrect because the passage states that Trisomy 21 is the most common form of mental retardation, not the only cause.
Choice (d) is incorrect because sexual underdevelopment can be caused by many conditions, not just Trisomy 21.

QUESTION-2. The correct answer is (d). The passage tells us that as women age they have a greater likelihood of carrying a child with Down Syndrome. If today's couples are postponing childbirth, then it could explain why today's couples see a higher incidence of Down Syndrome offspring.
Choice (a) is incorrect because if the population growth is decreasing, there should be fewer incidents of Down Syndrome.
Choice (b) is incorrect because the passage contains no information concerning a link between drug abuse and Down Syndrome.
Choice (c) is incorrect because people with Down Syndrome have a very small chance of reproducing successfully. So, while this answer could produce a small increase in Down syndrome, the actual number of cases would be statistically very low and would not likely lead to the conclusion that Down Syndrome has been steadily increasing in the last 10 years.
Choice (e) may be true, but nothing in the passage suggests that it would lead to a higher likelihood of babies with Down Syndrome.

QUESTION-3. The correct answer is (c). The passage says that those afflicted with Down Syndrome may be sexually underdeveloped, which could certainly contribute to the inability to conceive but may not necessarily impact the physical ability to engage in sexual intercourse.
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Joined: 07 Oct 2017
Posts: 29
Re: Down Syndrome is the most common serious birth defect afflicting child  [#permalink]

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08 Nov 2019, 23:54
2
Question 1: Option B is correct since:
Aneuploidy means either 1 or 3 chromosomes, while trisomy 21 means the presence of an additional 21 chromosome. And trisomy 21 is a feature of Down syndrome. So option B. the other factors (such as mental retardation) are the characteristics of Down syndrome

Question 2: Option C since
the third para states that incidence of Down syndrome increases with increasing mother's age of conceiving a child. So, if incidence has increased, then females are conceiving late

Question 3: Option C (from 2nd para) since
A is incorrect as its not inability rather people with Down syndrome are rarely able to copulate
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Re: Down Syndrome is the most common serious birth defect afflicting child  [#permalink]

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29 Mar 2020, 21:13
+1 Kudos to posts containing answer explanation of all questions
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Re: Down Syndrome is the most common serious birth defect afflicting child   [#permalink] 29 Mar 2020, 21:13