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After hearing this information, should Sue and Tim feel that their chances of having a child with a cleft lip are increased over that of the general population? Sue and Tim were referred for genetic counseling after they inquired about the risk of having a child with a cleft lip. Tim was born with a mild cleft lip that was surgically repaired. He expressed concern that his future children could be at risk for a more severe form of clefting. Sue was in her 12th week of pregnancy, and both were anxious about the pregnancy because Sue had had a difficult time conceiving. The couple stated that they would not consider terminating the pregnancy for any reason but wanted to be prepared for the possibility of having a child with a birth defect. The genetic counselor took a three-generation family history from both Sue and Tim and found that Tim was the only person to have had a cleft lip. Sue’s family history showed no cases of cleft lip. Tim and Sue had several misconceptions about clefting, and the genetic counselor spent time explaining how cleft lips occur and some of the known causes of this birth defect. The following list summarizes the counselor’s discussion with the couple. Fathers, as well as mothers, can pass on genes that cause clefting. Some clefts are caused by environmental factors, meaning that the condition didn’t come from the father or the mother. One child in 33 is born with some sort of birth defect. One in 700 is born with a cleft-related birth defect. Most clefts occur in boys; however, a girl can be born with a cleft. If a person (male or female) is born with a cleft, the chances of that person having a child with a cleft, given no other obvious factor, is 7 in 100. Some clefts are related to identifiable syndromes. Of those, some are autosomal dominant. A person with an autosomal dominant gene has a 50% probability of passing the gene to an offspring. Many clefts run in families even when there does not seem to be any identifiable syndrome present. Clefting seems to be related to ethnicity, occurring most often among Asians, Latinos, and Native Americans (1 : 500); next most often among persons of European ethnicity (1 : 700); and least often among persons of African origin (1 : 1,000). A cleft condition develops during the fourth to the eighth week of pregnancy. After that critical period, nothing the mother does can cause a cleft. Sometimes a cleft develops even before the mother is aware that she is pregnant. Women who smoke are twice as likely to give birth to a child with a cleft. Women who ingest large quantities of vitamin A or low quantities of folic acid are more likely to have children with a cleft. In about 70% of cases, the fetal face is clearly visible using ultrasound. Facial disorders have been detected at the 15th gestational week of pregnancy. Ultrasound can be precise and reliable in diagnosing fetal craniofacial conditions.

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Human Heredity: Principles and Iss...

11th Edition
Michael Cummings
Publisher: Cengage Learning
ISBN: 9781305251052

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BuyFindarrow_forward

Human Heredity: Principles and Iss...

11th Edition
Michael Cummings
Publisher: Cengage Learning
ISBN: 9781305251052
Chapter 5, Problem 1CS
Textbook Problem
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After hearing this information, should Sue and Tim feel that their chances of having a child with a cleft lip are increased over that of the general population?

Sue and Tim were referred for genetic counseling after they inquired about the risk of having a child with a cleft lip. Tim was born with a mild cleft lip that was surgically repaired. He expressed concern that his future children could be at risk for a more severe form of clefting. Sue was in her 12th week of pregnancy, and both were anxious about the pregnancy because Sue had had a difficult time conceiving. The couple stated that they would not consider terminating the pregnancy for any reason but wanted to be prepared for the possibility of having a child with a birth defect. The genetic counselor took a three-generation family history from both Sue and Tim and found that Tim was the only person to have had a cleft lip. Sue’s family history showed no cases of cleft lip. Tim and Sue had several misconceptions about clefting, and the genetic counselor spent time explaining how cleft lips occur and some of the known causes of this birth defect. The following list summarizes the counselor’s discussion with the couple.

  • Fathers, as well as mothers, can pass on genes that cause clefting.
  • Some clefts are caused by environmental factors, meaning that the condition didn’t come from the father or the mother.
  • One child in 33 is born with some sort of birth defect.
  • One in 700 is born with a cleft-related birth defect.
  • Most clefts occur in boys; however, a girl can be born with a cleft.
  • If a person (male or female) is born with a cleft, the chances of that person having a child with a cleft, given no other obvious factor, is 7 in 100.
  • Some clefts are related to identifiable syndromes. Of those, some are autosomal dominant. A person with an autosomal dominant gene has a 50% probability of passing the gene to an offspring.
  • Many clefts run in families even when there does not seem to be any identifiable syndrome present.
  • Clefting seems to be related to ethnicity, occurring most often among Asians, Latinos, and Native Americans (1 : 500); next most often among persons of European ethnicity (1 : 700); and least often among persons of African origin (1 : 1,000).
  • A cleft condition develops during the fourth to the eighth week of pregnancy. After that critical period, nothing the mother does can cause a cleft. Sometimes a cleft develops even before the mother is aware that she is pregnant.
  • Women who smoke are twice as likely to give birth to a child with a cleft.
  • Women who ingest large quantities of vitamin A or low quantities of folic acid are more likely to have children with a cleft.
  • In about 70% of cases, the fetal face is clearly visible using ultrasound. Facial disorders have been detected at the 15th gestational week of pregnancy. Ultrasound can be precise and reliable in diagnosing fetal craniofacial conditions.

Summary Introduction

To determine: Whether the chances of Ms. S and Mr. T having a child with a cleft lip is increased over the general population.

Introduction: Ms. S was 12 weeks pregnant. Mr. T was born with a mild cleft lip which was surgically repaired, but there was no similar past family history. Ms. S’s family history had no cases of cleft lip. They were concerned if their future child would be born with a more severe form of clefting. They had several misconceptions about clefting, which were cleared to them by the genetic counselor.

Explanation of Solution

The chances of Ms. S and Mr. T having a child with a cleft lip are not much evident because of the following reasons:

  • With reference to the case study, a person with an autosomal dominant gene has a 50% probability of passing the gene to an offspring. Ms. S and Mr. T do not have any family history of cleft lip, which implies that there are no genes that can predispose their child to the cleft lip.
  • Mr. T was the only one in the family who had a cleft lip. His development of cleft lip is most likely due to the environmental factors. Moreover, there are only 7 in 100 cases of a child born with a cleft lip if one of the parents had a history of cleft lip.

Hence, it can be concluded that Ms. S and Mr. T should not be worried about their child to develop a cleft lip as the chances are quite low.

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