Nokea
A father with an X-linked recessive disorder asks the nurse what the probability is that his sons will have the disorder. Which response should the nurse make?
- A. Male children will be carriers.
- B. All male children will be affected.
- C. None of the sons will have the disorder.
- D. It cannot be determined without more data.
Correct Answer: C
Rationale: When a male has an X-linked recessive disorder, he has one copy of the allele on his X chromosome. The father passes only his Y chromosome (not the X chromosome) to his sons. Therefore, none of his sons will have the X-linked recessive gene. They will not be carriers or be affected by the disorder. No additional data are needed to answer this question.
You may also like to solve these questions
A couple expecting their first child has a positive family history for several congenital defects and disorders. The couple tells the nurse that they are opposed to abortion for religious reasons. Which should the nurse consider when counseling the couple?
- A. The couple should be encouraged to have recommended diagnostic testing.
- B. The couple needs counseling regarding advantages and disadvantages of pregnancy termination.
- C. Diagnostic testing is required by law in this situation.
- D. Diagnostic testing is of limited value if termination of pregnancy is not an option.
Correct Answer: A
Rationale: The benefits of prenatal diagnostic testing extend beyond decisions concerning abortion. If the child has congenital disorders, decisions can be made about fetal surgery if indicated. In addition, if the child is expected to require neonatal intensive care at birth, the mother is encouraged to deliver at a level III neonatal center. The couple is counseled about the advantages and disadvantages of prenatal diagnosis, not pregnancy termination, although the family cannot be forced to have prenatal testing. The information gives the parents time to grieve and plan for their child if congenital disorders are present. If the child is free of defects, then the parents are relieved of a major worry.
Which genetic term refers to a person who possesses one copy of an affected gene and one copy of an unaffected gene and is clinically unaffected?
- A. Allele
- B. Carrier
- C. Pedigree
- D. Multifactorial
Correct Answer: B
Rationale: An individual who is a carrier is asymptomatic but possesses a genetic alteration, either in the form of a gene or chromosome change. Alleles are alternative expressions of genes at a different locus. A pedigree is a diagram that describes family relationships, gender, disease, status, or other relevant information about a family. Multifactorial describes a complex interaction of both genetic and environmental factors that produce an effect on the individual.
Parents ask the nurse if there was something that should have been done during the pregnancy to prevent their childs cleft lip. Which statement should the nurse give as a response?
- A. This is a type of deformation and can sometimes be prevented.
- B. Studies show that taking folic acid during pregnancy can prevent this defect.
- C. This is a genetic disorder and has a 25% chance of happening with each pregnancy.
- D. The malformation occurs at approximately 5 weeks of gestation; there is no known way to prevent this.
Correct Answer: D
Rationale: Cleft lip, an example of a malformation, occurs at approximately 5 weeks of gestation when the developing embryo naturally has two clefts in the area. There is no known way to prevent this defect. Deformations are often caused by extrinsic mechanical forces on normally developing tissue. Club foot is an example of a deformation often caused by uterine constraint. Cleft lip is not a genetic disorder; the reasons for this occurring are still unknown. Taking folic acid during pregnancy can help to prevent neural tube disorders but not cleft lip defects.
Which is a birth defect or disorder that occurs as a new case in a family and is not inherited?
- A. Sporadic
- B. Polygenic
- C. Monosomy
- D. Association
Correct Answer: A
Rationale: Sporadic describes a birth defect previously unidentified in a family. It is not inherited. Polygenic inheritance involves the inheritance of many genes at separate loci whose combined effects produce a given phenotype. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. A nonrandom cluster of malformations without a specific cause is an association.
Parents ask the nurse about the characteristics of autosomal dominant inheritance. Which statement is characteristic of autosomal dominant inheritance?
- A. Females are affected with greater frequency than males.
- B. Unaffected children of affected individuals will have affected children.
- C. Each child of a heterozygous affected parent has a 50% chance of being affected.
- D. Any child of two unaffected heterozygous parents has a 25% chance of being affected.
Correct Answer: C
Rationale: In autosomal dominant inheritance, only one copy of the mutant gene is necessary to cause the disorder. When a parent is affected, there is a 50% chance that the chromosome with the gene for the disorder will be contributed to each pregnancy. Males and females are equally affected. The disorder does not skip a generation. If the child is not affected, then most likely he or she is not a carrier of the gene for the disorder. In autosomal recessive inheritance, any child of two unaffected heterozygous parents has a 25% chance of being affected.