Genetics Questions

Genetics Questions 1) A man who has achondroplasia (Autosomal dominant) marries a phenotypically normal woman. If they have four children, what is the probability that none of their children will be affected with this disorder? What is the probability that all of them will be affected? Respectively. A. 1 1 , 4 4 B. 1 1 , 16 8 C. 1 1 , 16 16 D. 1 1 , 8 16 2) The estimated penetrance for familial retinoblastoma is approximately 90%. If a man has had familial retinoblastoma and mates with a woman who does not have a retinoblastoma mutation, what is the risk that their offspring will develop retinoblastoma? A. 0.5 B. 0.45 C. 0.25 D. 0.333 3) A 30-year-old woman had a sister who died from infantile Tay–Sachs disease, an autosomal recessive disorder that is fatal by age 6 years. What is the probability that this woman is a heterozygous carrier of the Tay–Sachs mutation? A. 2 3 B. 1 2 C. 1 4 D. 3 4 4) A man has neurofibromatosis type 1 (AD). His mother also has this condition. What is the probability that his sister also has this disease? In the absence of knowledge of his sister’s phenotype, what is the probability that his sister’s daughter has neurofibromatosis type 1? Respectively. A. 2 3 , 1 4 B. 1 2 ,2 C. 1 4 ,4 D. 1 2 , 1 1 1 4 5) Consider a woman who is a known heterozygous carrier of a mutation that causes PKU (autosomal recessive). What is the probability that her two grandchildren, who are first cousins, are both heterozygous carriers of this PKU-causing allele? Suppose instead that the woman is affected with PKU. Now what is the probability that both of her grandchildren carry the diseasecausing allele? A. 1 1 , 4 2 B. 1 1 , 8 4 C. 1 1 , 16 4 D. 1 1 , 16 8 6) Two mating individuals, labelled A and B in this figure, share a single great-grandparent. Suppose that one member of this couple is a heterozygous carrier for PKU. What is the probability that this couple will produce a child affected with PKU? A. 1 64 B. 1 4 C. 1 256 D. 1 32 7) The figure aside shows the inheritance of hemophilia A (X-linked recessive) in a family. What is the risk that the male in generation IV is affected with hemophilia A? What is the risk that the female in generation IV is a heterozygous carrier? A. 50%, 50% B. 100%, 50% C. 100%, 100% D. 50%, 0% 8) A boy and his brother both have hemophilia A (X-linked recessive). If there is no family history of hemophilia A in previous generations, what is the probability that the boys’ aunt (the mother’s sister) is a heterozygous carrier of the disease gene? A. 1 4 B. 2 3 C. 1 D. 9) 1 2 Rank the following individuals, from lowest to highest, in terms of the risk of producing a child with Down syndrome: Person 1] 45-year-old woman with no previous family history of Down syndrome Person 2] 25-year-old woman who has had one previous child with Down syndrome. Person 3] 25-year-old male carrier of a 21/14 Robertsonian translocation Person 4] 25-year-old female carrier of a 21/14 Robertsonian translocation A. 2<3<4<1 B. 2<3<1<4 C. 3<4<1<2 D. 1<3<4<2 10) A man with hemophilia A (X-linked recessive) and a normal woman produce a child with Turner syndrome (45,X). The child has normal factor VIII activity. Which of the following is true? A. The meiotic error must have occurred in the mother B. The father must have passed his X chromosome to the child C. The meiotic error must have occurred in the father D. None of the above **SNP (Single nucleotide polymorphism) & STR (short tandem repeat polymorphism) are biomarkers used to track the inheritance of disease genes within families. 11) Study the family shown in the pedigree. Individual 3 has PKU, an autosomal recessive disease. A two-allele SNP closely linked to the PKU locus has been assayed for each family member, and the figure shows the genotypes of each individual. Based on the genotypes of the linked marker, individual 6 A. is affected B. is a heterozygous carrier C. is a normal homozygote D. Data given isn’t enough 12) Study the family shown in the pedigree. The affected individuals have neurofibromatosis type 1 (NF1), an autosomal dominant condition. A four-allele STR locus closely linked to the NF1 locus has been typed for each family member. Based on the genotypes shown in the accompanying figure, is individual 6 A. is affected B. is normal 13) In this pedigree for an autosomal dominant disorder, a tightly linked two-allele SNP has been typed in each family member. Based on this information, what is the risk that the offspring in generation III will develop the disorder? A. 100% B. 25% C. 0% D. 50% 14) Mary’s two brothers and her mother’s brother all had Duchenne muscular dystrophy (DMD) (Xlinked recessive) and are now dead. Based on only this information, what is the probability that Mary is a heterozygous carrier for this disorder? What is the probability that she will produce affected offspring? Respectively A. 1 1 , 2 4 B. 2 3 , 3 4 C. 1 1 , 2 2 D. 1 3 , 2 4 15) (By Nabil) Assuming a gene gives rise to an mRNA consisting of 4 exons. Exon 1 codes for 80 amino acids, Exon 2 codes for 100 amino acids, Exon 3 codes for 40 amino acids, Exon 4 codes for 70 amino acids. If a p. Trp90Ter mutation occurs, what is the most likely fate of the mutated mRNA? A. Translated into a truncated protein product B. Non-sense mediated decay (NMD) 16) A 15-year-old male comes to the physician for a sports physical prior to joining the basketball team at his high school. He states that he occasionally gets chest pain and palpitations with exercise. His family history is significant for his father passing away at age 29 years from an aortic dissection. His temperature is 37 oc (98.60F), pulse is 89/min, respirations are 17/min, and blood pressure is 122/68 mm Hg. Physical examination shows he is a tall male with disproportionately long limbs. On auscultation of the heart, there is a mid-systolic click, followed by a late 3/6 systolic murmur. Which of the following is the most likely probability of this patient's offspring also inheriting this syndrome? A. 0% B. 25% C. 33% D. 50% E. 100% 17) An 8-year-old boy is brought to his pediatrician for follow-up of intellectual disability and hyperactivity. His temperature is 36.90C (98.50F), pulse is 89/min, respirations are 20/min, and blood pressure is 108/58 mm Hg. Physical examination shows the patient has a long, narrow face, prominent forehead and jaw, flexible fingers, and large ears. His mother has mild intellectual disability but there is no other family history of intellectual disability. Detection A. Absence of expression in paternal chromosome 15q11.2-13 B. Expansion of a trinucleotide CGG repeat in the 5’ untranslated region C. Genetic defect in the gene responsible for the production of dystrophin D. Karyotype demonstrating 3 copies of chromosome 21 E. Karyotype demonstrating XXY 18) A couple goes to a genetic counselor for family planning advice. Both male and female partners are of northern European ancestry and are concerned about offspring with cystic fibrosis, even though neither has a family history of the disease. The counselor learns that they recently heard of a family in their community whose son has cystic fibrosis. The counselor explains that the incidence of cystic fibrosis among populations of northern European ancestry is 1/2,500. Which of the following is the likelihood that this woman is a carrier for the cystic fibrosis gene mutation? A. 1 25 B. 1 50 C. 2 2500 D. 1 2500 1 2 ) 2500 E. ( 19) A 5-year-old boy is brought to the physician because of yellow, soft, slightly raised bumps on his eyelids. Both parents have a history of hypercholesterolemia (LDL = 250-350 mg/dL) since childhood. The patient's lipid profile shows an LDL level of 600 mg/dL. If the patient grows up and has a child with a partner with no history of hypercholesterolemia, which of the following is the probability that their child will have hypercholesterolemia? A. 0% B. 25% C. 50% D. 75% E. 100% 20) A family with a 2-year-old boy with Down syndrome participate in a study to determine the mechanism underlying the trisomy in their son. DNA is obtained from both parents and the child. A microsatellite marker adjacent to the centromere of chromosome 21 allows the researchers to track the inheritance of the chromosome. Four alleles at a locus are seen: A, B, C, and D. The father is found to have an AC genotype; the mother a BD genotype; and the affected child ABC. Nondisjunction most likely occurred in which of the following? A. The child during the first mitotic division B. The father during meiosis I C. The father during meiosis II D. The mother during meiosis I E. The mother during meiosis II 21) A 3-year-old boy is brought to the physician because of difficulty climbing stairs and muscle fatigue. His parents have noted a progressive decline in his motor abilities over the last 5-6 months. He has also had delays in speech development. His temperature is 37 oc (98.60F), pulse is 104/min, respirations are 25/min, and blood pressure is 88/48 mm Hg. On physical examination, the patient has enlargement in the muscles of his calves and a waddling gait. There is weakness in his proximal muscles and when arising from the floor, the patient uses his hands to push himself to an upright position. Laboratory studies show an elevated creatinine kinase. The mode of inheritance of this boy's disease is most similar to which of the following inherited diseases? A. Cystic fibrosis B. Hemophilia A C. Huntington disease D. Fragile X syndrome E. Neurofibromatosis type 1 22) A 6-year-old boy is brought to the physician because concerns for his apparent developmental delay and behavioral issues at school. Physical examination shows an elongated face with large, protruding ears, flat feet, and hypotonia. His mother states that his brother has a similar condition, although his three sisters appear to be unaffected. This child's condition is most likely caused by which of the following genetic defects? A. CGG trinucleotide repeat expansion on a sex chromosome B. Genomic imprinting on chromosome 15 C. Microdeletion on chromosome 22 D. Mutation in the MECP2 gene E. Trisomy of chromosome 21 23) A 7-year-old girl is brought to the physician for a well-child examination. She has a history of developmental delay, particularly with language acquisition, and a seizure disorder. Her parents report she has a strange affect characterized by excessive laughter at inappropriate times and describe her as "happy." During the examination, she flaps her hands several times. Karyotyping demonstrates an apparently normal genotype with 46 chromosomes. Which of the following most likely explains this patient's condition? A. A point mutation in an autosome B. Confined placental mosaicism C. Expansion of a trinucleotide repeat D. Microdeletion in an autosome E. Random inactivation of the X chromosome 24) A 3-year-old boy is brought to the physician by his parents because of excessive clumsiness. He often loses his balance, falls down, and has difficulty rising. He also has difficulty running, and climbing stairs. His temperature is 37 oc (98.60F), pulse is 98/min, respirations are 25/min, and blood pressure is 88/48 mm Hg. Physical examination shows enlarged calves and wasting of thigh muscles. There is a weakness in his proximal muscles and when arising from the floor, the patient uses his hands to push himself to an upright position. A molecular genetic test shows defective dystrophin cytoskeletal protein. Which of the following individuals in the patient's family is most likely to also have this disease and be symptomatic? A. Father B. Father’s Brother C. Mother D. Mother’s brother E. Sister 25) A 15-year-old girl is brought to the physician by her mother because she is concerned that she has not started puberty. Her height is in the 5th percentile for her age. Physical examination shows a wide neck, widely spaced nipples, and Tanner stage I for both breast and pubic hair development. Compared to an unaffected female, this patient is at higher risk for developing which of the following conditions? A. Cystic fibrosis B. Duchenne muscular dystrophy C. Huntington disease D. Polycystic kidney disease E. Sickle cell disease 26) A 25-year-old woman comes to the physician with a mild form of hemophilia. Her father was also diagnosed with hemophilia, but none of her four brothers are affected. The gene most likely mutated in this patient displays which of the following types of inheritance pattern? A. Autosomal dominant B. Autosomal recessive C. Mitochondrial D. X-linked E. Y-linked 27) A couple from a remote town in rural Pennsylvania comes to the physician with their 4 children. Both parents have a normal complexion with brown hair. Of their 4 children, 2 have brown hair with fair skin and 2 have white hair and skin and light blue eyes. Physical examination of the 2 lighter children (black circle and square in the pedigree) shows nystagmus and strabismus. The family pedigree is shown. Which of the following is the probability that IV-3 is a carrier of this trait? A. 1 4 B. 1 3 C. 1 2 D. 2 3 E. 1 1 28) A 29-year-old woman at 11 weeks' gestation is brought to the emergency department because of premature contractions and vaginal bleeding. Ultrasound examination shows a nonviable fetus. Dilation and curettage is performed and the uterus is evacuated. Her doctor orders karyotype analysis of the aborted fetus. The result is most likely to reveal which of the following karyotypes? A. 47, XXY B. 47, XY, +13 C. 47, XY , +16 D. 47, XY , +18 E. 47, XY, +21 29) An investigator is evaluating a large number of families that have a disease caused by a small deletion on chromosome 15. In all individuals (both male and female) affected by the disease, the deletion is inherited from the father. Which of the following is the most likely explanation for this phenomenon? A. Genomic imprinting B. Mitochondrial inheritance C. Sex-dependant penetrance D. X-linked recessive inheritance E. Y-linked inheritance 30) A 6-year-old boy is brought to the physician by his parents because of mild intellectual disability. The parents state that their other son has a similar condition, and their three daughters appear to be normal. His temperature is 36.90C (98.50F), pulse is 89/min, Other bookmarks respirations are 20/min, and blood pressure is 108/58 mm Hg. Physical examination shows that the patient has a long, narrow face, and prominent forehead and jaw and large ears. Genetic analysis shows the expansion of a trinucleotide repeat on a single chromosome. The expansion is most likely to be located on which of the following chromosomes? A. X B. Y C. 13 D. 18 E. 21 31) A 26-month-old boy is brought to the physician by his parents because he has poor eye contact and keeps flapping his hands and chewing on them. He has delayed social, motor, and language skills. Physical examination shows a long narrow face, large ears, and flat feet. Which of the following best explains the findings seen in the boy? A. Expanded trinucleotide repeat B. Genomic imprinting C. Robertsonian translocation D. Trisomy 13 E. Trisomy 18 32) A 15-year-old boy is brought to the physician by his parents because of a failure to develop normal male secondary sexual characteristics. He is above normal height weight for his age. Physical examination shows small testes and gynecomastia. His parents report that he had to repeat the 8th and 9th grades and he is still struggling in his classes. This patient's condition is most likely to be related to which of the following genetic abnormalities? A. Deletion of a gene B. Nondisjunction of an autosomal chromosome C. Nondisjunction of a sex chromosome D. Reciprocal translocation E. Robertsonian translocation 33) A 12-year-old boy is brought to the physician by his parents for behavioral problems at school. His teachers say that he is inattentive and distracting others in his class. He has been held back for two school years due to failing grades. He has a history of developmental delays since birth. Family history is significant for premature ovarian insufficiency in his maternal aunt. Physical examination shows a long and narrow face, large ears, and a prominent chin. Genitourinary examination shows enlarged testicles. Which of the following is the most likely genetic mechanism for the disorder affecting this patient? A. Microdeletion syndrome B. Mitochondrial inheritance C. Reciprocal translocation D. Robertsonian translocation E. Triplet repeat expansion 34) A 42-year-old primigravid woman comes to the physician for a follow-up visit to receive the results of an amniocentesis. The physician explains that her child has a chromosomal abnormality that will likely result in intellectual disabilities and an increased risk for several other conditions including congenital heart defects and acute lymphoblastic leukemia. Her child most likely has which of the following chromosomal abnormalities? A. Trisomy 13 B. Trisomy 18 C. Trisomy 21 D. 45, XO E. 47, XXY 35) A newborn girl is born prematurely at 36 weeks' gestation. The mother is 28-years-old and lacked prenatal care. On physical examination, the newborn has hypotonia, microcephaly, wideset eyes with downward palpebral folds, a small jaw, and a high-pitched cry. Chromosomal analysis reveals 46,XX with a large deletion on the short arm of chromosome 5. Which of the following is the most likely additional finding in this patient? A. Duodenal atresia B. Obesity C. Renal cysts D. Ventricular septal defect E. Wilms tumor 36) A 10-year-old boy is brought to a geneticist because of concerns about continued poor performance in school. His mother states that two years earlier, another physician had obtained a blood sample to test him for genetic anomalies and the results were negative. His mother is requesting additional genetic testing. A skin biopsy is taken and his skin cells are assessed for chromosomal abnormalities. It is found that his skin cells are positive for trisomy 21 . Which of the following genetic mechanisms is most likely to account for the discrepancy between the two test results? A. Balanced translocation B. Mitotic loss during embryogenesis C. Mosaicism D. Reciprocal translocation E. Robertsonian translocation 37) A 12-year-old boy is brought to the emergency department after sustaining a fracture of his right ulna in a fall. His parents are concerned because he has had several bone fractures over the past 9 years. Physical examination shows a bluish tinge to the sclerae. Which of the following best explains this combination of findings? A. Allelic hetrogeneity B. Gain-of-function mutation C. Locus hetrogeneity D. Multiple mutations E. Pleiotropy 38) A 37-year-old man is afflicted with an X-Iinked dominant disease. He and his wife are considering having children. His wife is homozygous normal at the locus. If the penetrance of the disease genotype is 60%, which of the following is the probability that their daughters will be affected by this disorder? A. 0% B. 30% C. 50% D. 60% E. 70% 39) A male newborn born at 30 weeks' gestation is small for gestational age. Physical examination shows hypotonia and marked skeletal muscle and subcutaneous fat hypoplasia. His face has a pinched appearance with hypoplastic orbital ridges, short palpebral fissures, and a small mouth and jaw. The head is small with prominence of the occiput. The ears are low-set and malformed. The newborn's fists are clenched, with overlapping of the third and fourth fingers. Feet are flexed in a convex position. Which of the following is the most likely diagnosis? A. 47, XXY B. Triple X C. Trisomy 13 D. Trisomy 18 E. Trisomy 21 40) A male newborn has a small head, small eyes, and six fingers on each hand. A two-dimensional echocardiogram shows multiple congenital heart defects. Which of the following genetic conditions is most likely responsible for the findings seen in this newborn? A. Trisomy 13 B. Trisomy 18 C. Trisomy 21 D. XXY E. XYY 41) A 33-year-old man has an X-Iinked dominant disease. He and his wife are considering having children. His wife is homozygous normal at the affected locus. If the penetrance of the disease genotype is 60%, which of the following is the probability that their first child will be affected with this disorder? A. 0% B. 30% C. 50% D. 60% E. 70% 42) In a given population, a disease is almost exclusively observed in males and has an incidence of 1 out of every 2,500 live male births. Which of the following is the frequency of carriers within that population? A. 1 25 B. 1 50 C. 1 1125 D. 1 2500 E. 49 1125 43) A 10-month-old boy is brought to the physician because of listlessness, apparent mental deterioration, atrophy, and difficulty in swallowing. He appeared normal at birth, but at age 6 months, he began to startle at loud noises. He was previously able to sit, but can now no longer sit, roll over, or recognize his parents. Ophthalmologic examination shows a central red area of the retina surrounded by white tissue. Genetic testing reveals a mutation in the HEXA gene. If this patient's parents have another child, what is the most likely risk of the child having the same disease? A. 1 4 B. 1 2 C. 2 3 D. 3 4 E. Not elevated above that of the general population 44) A 33-year-old primigravid woman requests a consultation with a genetic counselor. She and her husband are both heterozygous for an autosomal dominant disorder for which the affected allele has 80% penetrance. Which of the following is the probability that their child will be genotypically normal? A. 20% B. 25% C. 36% D. 60% E. 80% 45) An autosomal recessive disease has a carrier frequency of 1/25 in a specific population. Which of the following is the most likely frequency of individuals expressing the disease in this population? A. 1 25 B. 1 50 C. 1 625 D. 1 2500 E. 1 5000 Answers 1 C 10 C 19 E 28 C 37 E 2 B 11 A 20 B 29 A 38 D 3 A 12 B 21 B 30 A 39 D 4 D 13 D 22 A 31 A 40 A 5 C 14 A 23 D 32 C 41 B 6 C 15 B 24 D 33 E 42 C 7 A 16 D 25 B 34 C 43 A 8 D 17 B 26 D 35 D 44 B 9 B 18 A 27 D 36 C 45 D