genetics practice questions

49. A pregnant woman and her husband are both heterozygous for achondroplastic dwarfism, an autosomal dominant disease. The nurse advises the couple that their unborn child has which of the following probabilities of being of normal stature? 1. 25% probability 2. 50% probability 3. 75% probability 4. 100% probability

ANS: 1 . 1. The child has a 25% probability of being of normal stature 2. The child has a 25% probability of being of normal stature 3. The child has a 25% probability of being of normal stature 4. The child has a 25% probability of being of normal stature.

85. A client is being interviewed prior to becoming pregnant. She states that she has a disease that is transmitted by mitochondrial inheritance. Which of the following statements is consistent with the client's disease? 1. 100% of her children will be affected 2. Only her female children will be affected 3. Each fetus will have a 50% probability of being affected 4. A fetus will only be affected if it inherits a similar gene from its father

ANS: 1 . 1. This statement is accurate. All of the woman's children will be affected 2. This statement is incorrect. All of the woman's children will be affected 3. This statement is incorrect. All of the woman's children will be affected 4. This statement is incorrect. All of the woman's children will be affected.

57. A client has just had an amniocentesis to determine whether or not her baby has an inheritable genetic disease. Which of the following interventions is highest priority at this time? 1. Assess the fetal heart rate 2. Check the client's temperature 3. Acknowledge the client's anxiety about the possible findings 4. Answer questions regarding the genetic abnormality.

ANS: 1 1. Assessing the fetal heart rate is the highest priority since, although rare, the fetus may have been injured during the procedure 2. Taking the client's temperature is not the most important action to take at this time 3. Psychosocial issues are always significant, but they must take a back seat to physiological assessments 4. It is important to answer all questions posed by clients but, again, these should be answered only after physiological interventions are completed.

52. A woman is a carrier for hemophilia, an X-linked recessive illness. Her husband has a normal genotype. The nurse can advise the couple that the probability that their daughter will have the disease is: 1. 0% probability 2. 25% probability 3. 50% probability 4. 75% probability

ANS: 1 1. The probability of the couple having a daughter with hemophilia is 0%. 2. The probability of the couple having a daughter with hemophilia is 0% 3. The probability of the couple having a daughter with hemophilia is 0% 4. The probability of the couple having a daughter with hemophilia is 0%.

71. A man has inherited the gene for familial adenomatous polyposis (FAP), an autosomal dominant disease. He and his wife wish to have a baby. Which of the following would provide the couple with the highest probability of conceiving a healthy child? 1. Amniocentesis 2. Chorionic villus sampling 3. Pre-implantation genetic diagnosis 4. Gamete intrafallopian transfer.

ANS: 3 1. Amniocentesis will provide the couple with information regarding the genetics of a fetus in utero 2. CVS will provide the couple with information regarding the genetics of a fetus in utero 3. Preimplantation genetic diagnosis will provide the couple with the highest probability of conceiving a healthy child 4. GIFT is a type of infertility procedure.

68. A woman is informed that she is a carrier for Tay Sachs disease, an autosomal recessive illness. What is her phenotype? 1. She has one recessive gene and one normal gene 2. She has two recessive genes 3. She exhibits all symptoms of the disease 4. She exhibits no symptoms of the disease.

ANS: 4 1. This is the woman's genotype. It is not the woman's phenotype 2. This is the genotype of a person with Tay-Sachs disease 3. This is the phenotype of a person with Tay-Sachs disease 4. This is the woman's phenotype.

81. A male client has green color blindness, an X-linked recessive genetic disorder. His wife has no affected genes. Which of the following statements by the nurse is true regarding the couple's potential for having a child who is color blind? 1. All male children will be color blind 2. All female children will be color blind 3. All male children will be carriers for color blindness 4. All female children will be carriers for color blindness.

ANS: 4 1. This response is incorrect. None of their male children will be green color blind 2. This response is incorrect. None of their female children will be green color blind 3. This response is incorrect. Males do not carry X-linked recessive traits 4. This response is correct

2. Which statements, if made by a male client with an X-linked recessive disorder, indicates correct understanding of transmission? 1. "All of my sons will be affected." 2. "My father had this disease and passed it on to me." 3. "I have a 50% chance of passing the gene to a daughter." 4. "If my daughter is a carrier, there is a 50% chance each of her sons will be affected."

ANS: 4 1. There is no male-to-male transmission of X-linked recessive disorders 2. The client's father could not have passed the disease to him, as there is no male-to-male transmission 3. All the client's daughters will inherit the X-linked recessive gene mutation from their father. They will be carriers of the X-linked recessive gene mutation and can pass the faulty gene on to their children 4. The carrier mother of an X-linked recessive disorder has a 50% chance that each of her sons will be affected with the disorder. There is also a 50% chance that she will pass the normal gene to each of her sons and a 50% chance that each of her daughters will become carriers.

55. A 10-week gravid states that her sister's son has been diagnosed with an X-linked recessive disease, muscular dystrophy. She questions the nurse about the disease. Which of the following responses is appropriate for the nurse to make? 1. "Because muscular dystrophy is inherited through the woman, it is advisable for you to see a genetic counselor." 2. "Muscular dystrophy usually occurs as a spontaneous mutation. It is very unlikely that your fetus is affected." 3. "Your child could only acquire muscular dystrophy if both you and your husband carried the gene. You need to check your husband's family history 4. "If you were to have an amniocentesis and it were to come out positive, I can recommend you to an excellent abortion counselor.

ANS: 1 1. Because muscular dystrophy is X-linked, if her sister is a carrier, she too may be a carrier. She should see a genetic counselor 2. It is unlikely that the muscular dystrophy developed as a spontaneous mutation 3. Muscular dystrophy is X-linked so the father's genetics will not affect the outcome 4. This response is inappropriate. The decision to abort a child with a disease is up to the parents. Each set of parents must be allowed to make the decision for themselves. Their decision is likely to be based on many things, including their ability to care for a mentally retarded child and the knowledge that their child is affected by a genetic disease. The nurse cannot make the assumption that the parents will decide to abort an affected child.

53. At her first prenatal visit, a woman relates that her maternal aunt has cystic fibrosis, an autosomal recessive illness. Which of the following comments is appropriate for the nurse to make at this time? 1. "We can check to see whether or not you are a carrier for cystic fibrosis." 2. "It is unnecessary for you to worry since your aunt is not a direct relation." 3. "You should have an amniocentesis to see whether or not your child has the disease." 4. "Please ask your mother whether she has ever had any symptoms of cystic fibrosis."

ANS: 1 1. It is possible that this woman is a carrier for cystic fibrosis. A genetic evaluation can be done to determine that possibility 2. The affected gene could have been transmitted to both the woman's mother and to the aunt 3. Only if both this woman and her partner are carriers is there a possibility of their child having CF. And, even if that were the case, the probability of the fetus having the disease would be 1 in 4, or 25%, because CF is an autosomal recessive disease. 4. This response is inappropriate. The mother could be a carrier of the CF gene (carriers are symptom free) so the client should be tested.

58. Once oogenesis is complete, the resultant gamete cell contains how many chromosomes? 1. 23 2. 46 3. 47 4. 92.

ANS: 1 1. The haploid number of chromosomes is 23, the normal number of chromosomes in the gametes—in this case, in the ovum 2. The diploid number of chromosomes is 46, the normal number of chromosomes in the cells of human beings. 3. Aneuploidy is characterized by a chromosomal number that is not equal to a multiple of the haploid number—that is, the number of chromosomes in the cell is NOT equal to 23, 46, 69, 92, and so on. Trisomy 21 (47 chromosomes) is an example of an aneuploid number, as is a chromosome number of 33 4. Polyploidy is characterized by a chromosomal number that is equal to twice, three times, four times, and so on, of the diploid number—that is, the number of chromosomes in the cell is equal to 92 (2 X 46), 138 (3 X 46), and so on.

70. Which statement by a gravid client who is a carrier for muscular dystrophy, an X-linked recessive disease, indicates that she understands the implications of her status? 1. "If I have a girl, she will be healthy." 2. "None of my children will be at risk of the disease." 3. "If I have a boy, he will be a carrier." 4. "I am going to abort my fetus because it will be affected."

ANS: 1 1. This response is correct. As can be seen on the Punnett square, female children of carriers may carry the disease but do not express the disease. 2. This response is incorrect. Male children are at risk of the disease 3. This response is incorrect. Only females are carriers of X-linked diseases 4. This response is incorrect. When reviewing X-linked recessive inheritance, the test taker must discuss the male and female probabilities independently. If the fetus is a female, she will be healthy— either with two normal genes or as a carrier. The probability of the males being affected, however, is 50/50—either healthy with two normal genes or with disease because of the normal Y mated with an affected "x." Accordingly, as can be seen in the square below, the probability of a male being affected is 50%

60. A genetic counselor's report states, "The genetic nomenclature for this fetus is 46, XX." How should the nurse who reads this report interpret the cytogenetic results? 1. The baby is female with a normal number of chromosomes 2. The baby is hermaphroditic male with female chromosomes 3. The baby is male with an undisclosed genetic anomaly 4. There is insufficient information to answer this question.

ANS: 1 1. This response is correct. The normal number of chromosomes is present—46—and the child is a female - XX 2. This response is incorrect. An example of the genetic nomenclature for a hermaphrodite is 46,XX/46,XY. This fetus has a mosaic genotype with some cells having two X chromosomes and some cells having 1 X and 1 Y chromosome 3. This response is incorrect. An example of a male with a genetic defect is 46,XY,16p13.3 The defect, as indicated in the nomenclature, is on the p arm of the 16th chromosome at location 13.3. 4. There is sufficient information to answer this question.

69. During a genetic evaluation, it is discovered that the woman is carrying one autosomal dominant gene for a serious late adult-onset disease while her partner's history is unremarkable. Based on this information, which of the following family members should be considered high risk and in need of genetic counseling? Select all that apply. 1. The woman's fetus 2. The woman's sisters 3. The woman's brothers 4. The woman's parents 5. The woman's partner.

ANS: 1, 2, 3, 4 1. The woman's fetus has a 1 in 2, or 50%, probability of having the gene 2. The woman's sisters have a 1 in 2, or 50%, probability of having the gene 3. The woman's brothers have a 1 in 2, or 50%, probability of having the gene 4. One of the woman's parents definitely has the gene. Since the age of onset can be as late as age 50, the parents' symptoms may not yet have appeared 5. It is unlikely that the woman's partner has the gene.

51. A client, G4 P4004, states that her husband has just been diagnosed with polycystic kidney disease (PKD), an autosomal dominant disease. The husband is heterozygous for PKD, while the client has no PKD genes. The client states, "I have not had our children tested because they have such a slim chance of inheriting the disease. We intend to wait until they are teenagers to do the testing." The nurse should base her reply on which of the following? 1. Because affected individuals rarely exhibit symptoms before age 60, the children should be allowed to wait until they are adults to be tested 2. The woman may be exhibiting signs of denial since each of the couple's children has a 50/50 chance of developing the disease 3. Because the majority of the renal cysts that develop in affected individuals are harmless, it is completely unnecessary to have the children tested 4. The woman's husband should be seen by a genetic specialist since he is the person who is carrying the affected gene.

ANS: 2 1. Symptoms usually appear in affected individuals in their 30s or 40s, but the symptoms can appear as early as childhood 2. This response is correct. The children have a 50/50 chance of developing PKD. Since the capital A connotes the dominant gene, the child needs only one affected gene to exhibit the disease. 3. This statement is untrue. PKD can be a very serious illness. Some patients with the disease will require dialysis and/or kidney transplants 4. This statement is inappropriate. The husband's genotype is already known.

29. A nurse is doing genetic counseling with a couple. The mother has Down syndrome and the father has no chromosomal abnormalities. What is the chance of their offspring being affected by this disorder? 1. 25% 2. 50% 3. 75% 4. 100%

ANS: 2 1. The chance of their offspring inheriting the trait would not be 25% 2. The chance of their offspring inheriting the trait would be 50% 3. The chance of their offspring inheriting the trait would not be 75% 4. The chance of their offspring inheriting the trait would not be 100%.

66. A woman who has had multiple miscarriages is advised to go through genetic testing. The client asks the nurse the rationale for this recommendation. The nurse should base his or her response on which of the following? 1. The woman's pedigree may exhibit a mitochondrial inheritance pattern. 2. The majority of miscarriages are caused by genetic defects 3. A woman's chromosomal pattern determines her fertility 4. There is a genetic marker that detects the presence of an incompetent cervix.

ANS: 2 1. The pedigree should be analyzed for any and all abnormal inheritance patterns 2. This is true. The incidence of miscarriage is very high, about 1 out of every 5 pregnancies, and the majority of miscarriages are related to a genetic defect 3. A woman's fertility is determined by many factors 4. This statement is not true. There is no genetic marker for incompetent cervix.

83. A client's amniocentesis results were reported as 46, XY. Her obstetrician informed her at the time that everything "looks good." Shortly after birth the baby is diagnosed with cerebral palsy. Which of the following responses will explain this result? 1. It is likely that the client received the wrong amniocentesis results. 2. Cerebral palsy is not a genetic disease 3. The genes that cause cerebral palsy have not yet been discovered. 4. The genetics lab failed to test for cerebral palsy.

ANS: 2 1. This information is unsupported by the scenario. Cerebral palsy is not a genetic defect and is not detected through amniocentesis 2. Cerebral palsy is not a genetic disease. It is caused by a hypoxic injury that can occur at any time during pregnancy, labor and delivery, or the postdelivery period 3. Cerebral palsy is not a genetic disease. It is caused by a hypoxic injury that can occur at any time during pregnancy, labor and delivery, or the postdelivery period 4. Cerebral palsy is not a genetic disease. It is caused by a hypoxic injury that can occur at any time during pregnancy, labor and delivery, or the postdelivery period.

65. A woman, who has undergone amniocentesis, has been notified that her baby is XX with a 14/21 Robertsonian chromosomal translocation. The nurse helps the woman to understand which of the following? 1. The baby will have a number of serious genetic defects 2. It is likely that the baby will be unable to have children when she grows up 3. Chromosomal translocations are common and rarely problematic. 4. An abortion will probably be the best decision under the circumstances.

ANS: 2 1. This response is incorrect. The child will likely be a normal-appearing female 2. Because there is a translocation in the child's chromosomal pattern, the child's gametes will likely contain an abnormal amount of genetic material and the child will be infertile 3. Translocations are usually not problematic for the first generation, but they can lead to significant defects and/or infertility in the next generation 4. The client must decide for herself whether or not to abort the fetus.

73. A 3-month-old baby has been diagnosed with cystic fibrosis. The mother states, "How could this happen? I had an amniocentesis during my pregnancy and everything was supposed to be normal!" What does the nurse understand about this situation? 1. Cystic fibrosis cannot be diagnosed by amniocentesis 2. The baby may have an uncommon genetic variant of the disease 3. It is possible that the laboratory technician made an error 4. Instead of obtaining fetal cells the doctor probably harvested maternal cells.

ANS: 2 1. This statement is not accurate. Cystic fibrosis can be detected via amniocentesis 2. This response is likely. The genetic tests that are performed only check for the most common genetic variants of many diseases, including CF. If the baby were positive for an uncommon variant, it would be missed 3. It is unlikely that the lab tech made a mistake 4. Although it is possible, it is unlikely that maternal cells were harvested rather than fetal cells

62. A woman is seeking genetic counseling during her pregnancy. She has a strong family history of diabetes mellitus. She wishes to have an amniocentesis to determine whether or not she is carrying a baby who will "develop diabetes." Which of the following replies by the nurse would be most appropriate for the nurse to make? 1. "Doctors don't do amniocenteses to detect diabetes." 2. "Diabetes cannot be diagnosed by looking at the genes." 3. "Although diabetes does have a genetic component, diet and exercise also determine whether or not someone is diabetic." 4. "Even if the baby doesn't carry the genes for diabetes, the baby could still develop the disease."

ANS: 3 1. Although this response is accurate, it is an inappropriate response for the nurse to make 2. Although this response is accurate, it is an inappropriate response for the nurse to make 3. This response is accurate. Diabetes is one of the many diseases that has both a genetic and an environmental component 4. Although this response is accurate, it is an inappropriate response for the nurse to make.

47. A woman has been advised that the reason why she has had a number of spontaneous abortions is because she has an inheritable mutation. Which of the following situations is consistent with this statement? 1. A client developed skin cancer after being exposed to the sun 2. A client developed colon cancer from an inherited dominant gene 3. A reciprocal translocation was reported on a client's genetic analysis 4. A client's left arm failed to develop when she was a fetus.

ANS: 3 1. The DNA in the client's skin cells did mutate, but the mutation will not affect the client's fertility because the woman's ovaries were not affected 2. The inherited gene affects a client's risk of contracting colon cancer. It will not affect fertility 3. A reciprocal translocation can result in infertility 4. Failure of one arm to develop in utero is related to an environmental insult rather than a genetic insult.

64. A woman asks a nurse about presymptomatic genetic testing for Huntington's disease. The nurse should base her response on which of the following? 1. There is no genetic marker for Huntington's disease 2. Presymptomatic testing cannot predict whether or not the gene will be expressed 3. If the woman is positive for the gene for Huntington's, she will develop the disease later in life 4. If the woman is negative for the gene, her children should be tested to see whether or not they are carriers.

ANS: 3 1. There is a genetic marker for Huntington's disease 2. In the case of Huntington's disease, if a person has the gene and lives long enough, there is virtually a 100% probability he or she will develop the disease. The gene has a high degree of expressivity, or, in other words, people who carry the gene will develop the disease 3. This answer is correct, if a person has the gene and lives long enough, virtually 100% of the time the disease will develop and progress 4. There is no carrier state when a disease is transmitted via a dominant inheritance pattern, as is Huntington's disease

77. A woman who is a carrier for sickle cell anemia is advised that if her baby has two recessive genes, the penetrance of the disease is 100%, but the expressivity is variable. Which of the following explanations will clarify this communication for the mother? All babies with 2 recessive sickle cell genes will: 1. Develop painful vaso-occlusive crises during their first year of life. 2. Exhibit at least some signs of the disease while in the neonatal nursery 3. Show some symptoms of the disease but the severity of the symptoms will be individual 4. Be diagnosed with sickle cell trait but will be healthy and disease-free throughout their lives.

ANS: 3 1. This response is incorrect. No one can make such a prediction 2. Neonates virtually never exhibit signs of sickle cell because fetal hemoglobin does not sickle 3. This response is correct. Babies with two recessive sickle cell genes will show some symptoms of the disease but the severity of the symptoms will be individual 4. This response is incorrect. Virtually all children with sickle cell anemia will exhibit some symptoms during their lives

82. A woman whose blood type is O (negative) states, "My husband is AB (positive). What blood type will my baby have?" Which of the following is the best response for the nurse to make? 1. "Your baby could be type O but it is impossible to predict the Rh status." 2. "Your baby will be either AB (positive) or AB (negative)." 3. "Your baby could be any blood type except type O or type AB." 4. "Your baby will definitely be Rh (positive)."

ANS: 3 1. This response is incorrect. The baby will be either type A or type B. Type O is the recessive 2. This response is incorrect. The offspring cannot be type AB since the mother is type O 3. This response is correct. The offspring could be blood type AO (type A) or BO (type B), but it cannot be type O since the father is AB and cannot be type AB since mother is type O 4. The baby could be either Rh+ (positive) or Rh- (negative), depending on whether or not the father is heterozygous for the Rh factor.

50. A couple inquires about the inheritance of Huntington's disease (HD) because the prospective father's mother is dying of the illness. There is no history of the disease in his partner's family. The man has never been tested for HD. Which of the following responses by the nurse is appropriate? 1. "Because HD is an autosomal dominant disease, each and every one of your children will have a 1 in 4 chance of having the disease." 2. "Because only one of you has a family history of HD, the probability of any of your children having the disease is less than 10%." 3. "Because HD is such a devastating disease, if there is any chance of passing the gene along, it would be advisable for you to adopt." 4. "Because neither of you has been tested for HD, the most information I can give you is that each and every one of your children may have the disease."

ANS: 4 . 1. If the prospective father possesses the gene, the probability of their children inheriting the gene is 1 in 2, or 50%. Since the man has not been tested, it is impossible to determine the probabilities. 2. This statement is completely false 3. It is improper for the nurse to recommend that the clients not have children. It is the couple's choice whether or not to get pregnant. It is the nurse's responsibility to give as accurate information as possible 4. This statement is correct. No specific information can be given until or unless the potential father decides to be tested.

56. The genetic counselor informs a couple that they have a 25% probability of getting pregnant with a child with a severe genetic disease. The couple asks the nurse exactly what that means. Which of the following responses by the nurse is appropriate? 1. Their first child will have the genetic disease 2. If they have four children, one of the children will have the disease. 3. Their fourth child will have the genetic disease 4. Whenever they get pregnant, the fetus may have the disease.

ANS: 4 1. Each pregnancy has its own probability so it is impossible to predict which, if any, child will or will not have the disease 2. Each pregnancy has its own probability so it is possible for all or none of the children to have the disease 3. Each pregnancy has its own probability so it is impossible to predict which, if any, child will or will not have the disease 4. This is true. Every time the woman gets pregnant there is a possibility (25% chance) that she is carrying a child with the disease.

87. A woman is pregnant. During amniocentesis it is discovered that her child has Down syndrome with a mosaic chromosomal configuration. She asks the nurse what that means. What is the nurse's best response? 1. "Instead of two number 21 chromosomes, your child has three." 2. "Your baby's number 21 chromosomes have black and white bands on them." 3. "Some of your baby's number 21 chromosomes are longer than others." 4. "Some of your baby's cells have two number 21 chromosomes and some have three."

ANS: 4 1. This is the definition of Down syndrome, but not of Down syndrome with mosaic chromosomal configuration. 2. All chromosomes are banded. 3. The number 21 chromosomes are of normal length in Down syndrome 4. Mosaicism is characterized by the fact that some of the cells of the body have the abnormal number of chromosomes but some of the cells have the normal number. This may happen with rapid disjunction. In Down syndrome, it means that some of the cells have three number 21 chromosomes and some have the normal number of two number 21 chromosomes. Mosaicism is not specific to Down syndrome but can occur with other chromosomal abnormalities

20. A couple has just been told their child has an autosomal recessive inheritance disorder. Which statement by the nurse best describes this genetic disorder? 1. "Your child has a disorder in which a single gene controls the particular trait." 2. "Your child has a disorder in which the abnormal gene is carried on the X chromosome." 3. "Your child has a disorder in which the abnormal gene for the disorder is expressed even when the other member of the pair is normal." 4. "Your child has a disorder in which both genes of a pair must be abnormal for the disorder to be expressed."

ANS: 4 1. This would not be an autosomal inheritance 2. This would be an X-linked inheritance. Autosomal inheritance would be any chromosome other than the sex (X and Y) chromosomes 3. A child needs to inherit only one changed replica of the gene pair in order to be affected with an autosomal dominant disorder 4. Autosomal recessive inheritance disorders exist when two mutated genes, one from each parent, are passed on to their offspring.