The germ cells in the testicular tubules are actively dividing in the process of spermatogenesis. A haploid set of chromosomes is formed in meiosis at the end of which of the following phases?
A Metaphase II
B Prophase I
C Interphase II
D Telophase I
E Anaphase II
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A cell culture contains fibroblasts which are actively dividing. The amount of DNA becomes doubled at the end of which portion of the cell cycle?
A G0
B G1
C S
D G2
E M
The process of gametogenesis is occurring in the ovary. A secondary oocyte in the fallopian tube, just after fertilization, is in which of the following phases?
A Interphase II
C Anaphase II
E Metaphase II
A 25-year-old man and his 24-year-old wife have a baby boy who has a problem with bowel obstruction soon after birth, but an otherwise uneventful infancy. In childhood, however, their son has a succession of respiratory tract infections. Laboratory workup fails to reveal an immunologic deficit. Their daughter, born two years later, does not have these problems. There is no family history for this disorder. Their son is infertile; their daughter gives birth to a son and daughter, both of whom are not affected by this disorder. Which of the following is the most likely pattern of inheritance for this family?
A Autosomal dominant
B Autosomal recessive
C Dominant negative
D X-linked recessive
E Spontaneous new mutation
A 40-year-old man has a myocardial infarction. Screening for risk factors reveals that he has a total serum cholesterol of 326 mg/dL. His wife is found to have a total serum cholesterol of 397 mg/dL. They have a son who suffers a myocardial infarction at age 22, and in him the total serum cholesterol is 729 mg/dL. The condition that underlies these findings is most likely to be inherited in a manner which illustrates which of the following patterns?
A Autosomal recessive
B X-linked recessive
C Autosomal dominant with reduced penetrance
D Dominant negative
E Dosage sensitivity
A missense mutation is found to have an incidence of 1/100,000 persons. It involves a single amino acid in a gene encoding for an enzyme. This mutation is most likely to be manifested by which of the following patterns of inheritance?
C X-linked recessive
E Multifactorial
The pedigree is shown here for a family with a history of an inherited disorder with onset in the 4th or 5th decade. This disorder is characterized by uncontrollable choreiform movements. Which of the following inheritance patterns is most likely to be present in this family?
A Variable expression
B Reduced penetrance
C X-linked inheritance
D Somatic mosaicism
E Dominant negative
The pedigree shown here for a family with an inherited disorder. Some members of the family manifest with the disorder in childhood, but they can be effectively treated if diagnosed. This pattern is most consistent for which of the following conditions?
A Cystic fibrosis
B Marfan syndrome
C Familial hypercholesterolemia
D Hemophilia A
E Achondroplasia
A 2-year-old child is brought to the physician by his parents because he is not growing normally. Both parents are tall (father 193 cm, or 6' 4" and mother 180 cm, or 5' 11") but the child is below the 5th percentile for height for his age. On physical examination his decreased height is primarily due to shortened extremities. The child is neurologically normal, and he is developing motor and verbal skills normally. There is no family history of other children being small on either side of the family. The parents are pointing fingers at each other in regard to infidelity. Which of the following genetic conditions is most likely to explain this set of findings?
A Autosomal recessive condition
B X-linked recessive condition
C Variable expressivity
D Uniparental disomy
An epidemiologic study of sickle cell anemia is performed. The incidence of sickle cell anemia amongst African-Americans in the U.S. is found to be 1 in 625. Based upon this finding, which of the following is the most likely carrier rate for this condition in the U.S. African-American population?
A 2%
B 8%
C 25%
D 33%
E 50%
A baby is born at term to a 23-year-old mother. The baby is normal in size. On newborn physical examination, a single midline cleft lip is noted. There are no other congenital anomalies. There is no family history of cleft lip or other birth defects. The parents want to know what the risk will be for this condition if they decide to have more children. Which of the following is the best estimate to give them for a recurrence risk?
A 1%
B 5%
D 50%
E 100%
A population-based study of mental disorders is conducted. A mental disorder is found that is characterized by periods of hyperactivity followed by periods of sluggishness and inactivity. This disorder is observed in monozygous twins at a higher rate than for dizygous twins or for the general population. This disorder is most likely to represent an increased risk for which of the following?
A Empirical risk
B Brain malformation
C Concordance
D Threshold of liability
E Environmental influence
A clinical study is performed to analyze the effectiveness of measures to prevent skin cancer in a population. The use of sunscreen when outdoors for long periods of bright sun is shown to reduce the risk for skin cancer. This risk reduction is mostly likely to occur when which of the following cellular genetic abnormalities events happens less frequently?
A Non-disjunctional event
B Point mutation in a gene
C Pyrimidine dimer formation
D Chromosomal translocation
E Tumor suppressor gene activation activity
In a population donating blood for transfusion therapy, the distribution of blood types is found to be as follows:
A - 41%
B - 22%
O - 36%
AB -1%
Based upon these results, most persons who are blood group A:
A Are homozygotes
B Demonstrate codominance
C Represent the most common allele in U.S. causasians
D Will have more children with the O type
E Have a coagulopathy
A rare inborn error of metabolism involving an enzyme occurs in two males in the second generation and two females in the fourth generation of a family founded by two immigrants from the same country. Which of the following genetic mechanisms best explains why this could happen?
A Consanguinity
B Incomplete penetrance
C Spontaneous new mutation
E X-linked inheritance
A disorder is seen more frequently in the males of a particular family, with increasing incidence in successive generations. Some males are carriers. This pattern is most characteristic for which of the following inherited diseases?
A Familial hypercholesterolemia
B Fragile X syndrome
C Hemophilia A
D Marfan syndrome
E Prader-Willi syndrome
If the following sequence is found in a protein:
Glu-His-Phe-Pro-Thr-Arg
What type of mutation would be most likely to produce the following sequence?
Glu-His-Phe-Ala-His-Thr:
A Duplication
B Frameshift
C Missense
D Nonsense
E Splice site
A 43-year-old man develops the gradual onset of a debilitating movement disorder with awkward twisting and flailing movements of his extremities over the past 3 years. His mental function diminishes as well. MR imaging of his brain shows ex vacuo ventricular dilation with decreased size of the caudate nuclei. What is the most likely recurrence risk for inheritance of this disorder in his children?
A cell from a buccal smear from an adult woman is observed to have two Barr bodies. On physical examination she has no abnormal findings noted. Which of the following is her karyotype most likely to be?
A 46, XX
B 47, XXY
C 47, XXX
D 69, XXX
E 92, XXXX
A 29-year-old woman gives birth to a term infant. The baby is noted to have anomalies involving limbs, skull, and heart. Which of the following types of genetic alterations is most likely to lead to this appearance?
A Activation of an oncogene
B Extra Y chromosome
C Loss of an autosome
D Mutation in a gene coding for an enzyme
E Mutation in a transcriptional gene
A 22-year-old woman has developed progressive muscular weakness and central nervous system deterioration with ataxia and epilepsy over the past 10 years. She recently had an episode of loss of consciousness and loss of movement in her right arm, with difficulty speaking. There is a family history of the disease, with the following pedigree:
These findings are most consistent with an abnormality involving which of the following genes?
A Mitochondrial gene
B Structural gene
C Transcriptional gene
D Tumor suppressor gene
E X-linked gene
A 4-week-old infant boy develops projectile vomiting over the past 2 days. On physical examination he has no external anomalies noted. A firm mass is palpable in the mid-abdominal region. An operation is performed to relieve bowel obstruction at the pylorus. Which of his relatives is most likely to have manifested this same illness?
A Mother
B Father
C Sister
D Uncle
E Grandfather
A clinical study is performed to analyze the results of karyotyping of fetal cells obtained by amniocentesis between 16 and 19 weeks gestation. 53% of the samples have a 46, XX karyotype. Which of the following statements is the most appropriate interpretation of this finding?
A Hemophilia A cannot be manifested
B The possibility of a birth defect has been ruled out
C This pattern produces a phenotypic female
D Two Barr bodies will be present in somatic cells
E The analysis was performed on polar bodies
The shuffling of portions of chromosomes produces genetic diversity by increasing the possible combinations of human traits. This process occurs during which of the following stages of meiosis?
A Anaphase I
B Interphase I
C Metaphase II
D Prophase I
E Telophase II
Somatic cells in culture are growing and dividing normally. The amount of DNA is analyzed at different stages of the cell cycle. Doubling of the cellular DNA is most likely to occur during which of the following stages of mitosis?
A Anaphase
B Interphase
C Metaphase
D Telophase
E All phases
Several children in a family are affected by a disorder in which multiple dermal neurofibromas are present, along with cafe-au-lait spots. Based upon the pedigree shown here, what is the most likely pattern of inheritance?
A Autosomal dominant with reduced penetrance
B Genomic imprinting
C Germline mosaicism
E X-linked recessive
A disorder appears in each generation of a family. This disorder tends to be less severe in females. Based upon the following pedigree, which of the following inheritance patterns best explains this phenomenon?
D X-linked dominant
An infant boy is born at term with an immunodeficiency state and is found to have a deficiency of the enzyme adenine deaminase (ADA). The ADA enzyme is mainly produced in lymphoid cells. Which of the following therapies would offer the best long term prognosis for this infant?
A Adenovirus transfection
B Gene blocking
C Liposome vector
D Retroviral gene insertion
E Stem cell transplantation
A University establishes a satellite campus on Mars, with a small colony of 100 permanent residents. Within 10 generations, there is a population of 2000 persons in which about 10% of persons are blood group AB. Which of the following genetic patterns is most likely represented in this population?
A Dosage sensitivity
B Genetic drift
C Natural selection
D Variable expression
Over time, it is noted that the University colony on Mars has been receiving large shipments of diet soft drinks, boiled peanuts, and grits. The population of the colony is most likely exhibiting which of the following influences?
B Environment
C Imprinting
D Multifactorial inheritance
E Variable expression
A 23-year-old woman has been pregnant 4 times in the past 5 years. Two of the pregnancies ended in stillbirth. One of these stillbirths received a chromosome analysis, and the karyotype showed a 45, XX, -14 pattern. Of the three liveborn children, two have a 47, XX, +21 and 47, XY, +21 karyotype respectively. The third has a 46, XX karyotype. Which of the following genetic mechanisms is most likely to lead to these findings?
A Germline mosaicism
B Imprinting
C Maternal Robertsonian translocation
D Non-disjunctional event
E Uniparental disomy
A 33-year-old woman has had progressive muscular weakness and central nervous system deterioration with ataxia and epilepsy over the past 10 years. Laboratory studies show a serum lactate of 8 mmol/L. She develops suddne loss of consciousness. A family pedigree is shown:
Genes encoding for which of the following are most likely to be mutated in this family?
A Cell cycle regulation
B DNA repair
C Enzyme degradation
D Oxidative phosphorylation
E Structural protein
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