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Which genetic term refers to the transfer of all or part of a chromosome to a different chromosome after chromosome breakage?
- A. Trisomy
- B. Monosomy
- C. Translocation
- D. Nondisjunction
Correct Answer: C
Rationale: Translocation is the transfer of all or part of a chromosome to a different chromosome after chromosome breakage. It can be balanced, producing no phenotypic effects, or unbalanced, producing severe or lethal effects. Trisomy is an abnormal number of chromosomes caused by the presence of an extra chromosome, which is added to a given chromosome pair and results in a total of 47 chromosomes per cell. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. Nondisjunction is the failure of homologous chromosomes or chromatids to separate during mitosis or meiosis.
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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.
Which is a sex chromosome abnormality that is caused by the presence of one or more additional X chromosomes in a male?
- A. Turner
- B. Triple X
- C. Klinefelter
- D. Trisomy 13
Correct Answer: C
Rationale: Klinefelter syndrome is characterized by one or more additional X chromosomes. These individuals are tall with male secondary sexual characteristics that may be deficient, and they may be learning disabled. An absence of an X chromosome results in Turner syndrome. Triple X and trisomy 13 are not abnormalities that involve one or more additional X chromosomes in a male (Klinefelter syndrome).
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.
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.
Chromosome analysis of the fetus is usually accomplished through the testing of which?
- A. Fetal serum
- B. Maternal urine
- C. Amniotic fluid
- D. Maternal serum
Correct Answer: C
Rationale: Amniocentesis is the most common method to retrieve fetal cells for chromosome analysis. Viable fetal cells are sloughed off into the amniotic fluid, and when a sample is taken, they can be cultured and analyzed. It is difficult to obtain a sample of the fetal blood. It is a high-risk situation for the fetus. Fetal cells are not present in the maternal urine or blood.