🎯 Theme 7 Exam Practice

A 38-year-old patient develops progressive involuntary movements. Several relatives have the same disorder, but symptom onset occurred progressively earlier in successive generations. The responsible mutation alters gene function through an expanding repetitive DNA sequence. Which disorder is most consistent with this mechanism?

Which disorder is a typical example of autosomal dominant inheritance?

A student compares several inherited disorders and notes that mutations may affect enzymes, receptors, membrane transporters or structural proteins. Which sequence most accurately summarizes the common pathological principle linking these mutations to disease?

A patient has markedly elevated circulating LDL because cells cannot take up LDL normally. Which type of inherited molecular defect best explains this abnormality?

A woman with a mitochondrial genetic disorder has several affected children, while an affected man does not transmit the disorder to his children. Which inheritance pattern is demonstrated?

A pathogenic gene variant is suspected to produce an abnormally sized protein. The laboratory separates cellular proteins and then uses an antibody against the protein of interest to identify the abnormal product. Which technique is being used?

A woman carries a pathogenic variant responsible for an X-linked disorder. She has mild manifestations, while her affected brother has severe disease. Which biological phenomenon best explains the variable expression in the woman?

A patient receives a neuromuscular blocking drug during surgery and develops unexpectedly prolonged paralysis. Further investigation demonstrates an inherited abnormality of plasma cholinesterase. Which concept best explains this adverse response?

A single nucleotide substitution changes a codon so that a different amino acid is incorporated into a protein. Which type of mutation has occurred?

A patient carries a pathogenic gene variant, while the observable clinical characteristics produced by that variant are recorded during examination. What is the term for the observable characteristics?

A molecular laboratory is comparing two methods. Test X produces millions of copies of a selected DNA region, while Test Y demonstrates the chromosomal location of a selected DNA sequence using a fluorescent probe. Which pairing correctly identifies the tests?

A newborn is suspected of having Down syndrome based on characteristic physical findings. The clinician wants to determine whether the extra chromosome 21 material represents free trisomy, translocation or mosaicism. Which investigation is most appropriate for defining the chromosomal pattern?

A laboratory needs to produce many copies of a specific DNA sequence from a very small sample for further analysis. Which molecular technique is most appropriate?

A baby is born with a structural abnormality that developed during fetal life. The abnormality is present at birth but is not known to be inherited from either parent. Which term best describes the abnormality?

A 19-year-old man has tall stature, long limbs and cardiovascular abnormalities consistent with an inherited connective-tissue disorder. His father and paternal grandmother have similar findings. The mutant protein interferes with the function of protein produced by the normal allele. Which molecular mechanism best explains this pattern?

A newborn has hypotonia, characteristic facial features and a congenital cardiac defect. Chromosome analysis demonstrates additional chromosome 21 material attached to another chromosome rather than a free third chromosome 21. Which mechanism best explains this finding?

A child has a deletion of two nucleotides within the coding region of a gene. The downstream sequence of codons becomes altered. Which genetic abnormality best explains this effect?

A researcher studies a disease in which several genetic variants each contribute a small amount of susceptibility. Clinical disease develops more readily when these variants occur together with relevant environmental influences. Which model best describes this disorder?

Hypertension develops through the combined effect of several susceptibility genes and environmental influences. Which genetic category best describes this type of disorder?

A nucleotide substitution converts a codon specifying an amino acid into a premature termination signal. Which type of mutation is most likely?

A man with an X-linked disorder has children with a woman who does not carry the pathogenic variant. Which transmission pattern is expected from the affected father?

Two siblings with the same mitochondrial DNA mutation show markedly different severity of neurological and muscular dysfunction. One sibling has mild disease, while the other is severely affected. Which mechanism best explains this variation?

A medical student is reviewing a child with a disorder caused by a permanent change in the DNA sequence. Which term best describes this genetic change?

A newborn has hypotonia, characteristic facial features and a single transverse palmar crease. Cytogenetic analysis demonstrates three copies of chromosome 21. Which mechanism most commonly produces this abnormality?

A child has thick secretions involving several epithelial organs. Molecular analysis identifies an abnormal membrane protein involved in chloride movement. Which sequence best explains how the mutation produces the phenotype?

Two clinically healthy parents have an affected son and an affected daughter with the same inherited metabolic disease. Which transmission pattern best fits this family?

A boy has hemophilia A. His maternal uncle is also affected, while his father is healthy. Which inheritance pattern best explains this family history?

A pedigree shows affected individuals in several consecutive generations. Males and females are affected, and an affected father has an affected son. Which inheritance pattern is most likely?

A laboratory receives a very small DNA sample and needs to selectively increase the amount of one defined gene region before further analysis. After the DNA strands are separated, what must occur next during the amplification cycle?

Two clinically healthy parents have a child with an inherited metabolic disorder caused by severe deficiency of an enzyme. Each parent has approximately sufficient residual enzyme activity to remain clinically unaffected. Which principle best explains the parents' normal phenotype?

A child has an inherited metabolic disorder caused by deficiency of a specific enzyme. Which biochemical consequence is most likely?

A child with cystic fibrosis has abnormal movement of chloride across epithelial membranes. Which type of gene product is primarily defective?

A family shows a neurological disorder that develops at an earlier age and with increasing severity in successive generations. Which genetic mechanism best explains this pattern?

Why is father-to-son transmission absent in an X-linked disorder?

A child has clinical features of Down syndrome. Cytogenetic analysis shows two populations of cells: one with a normal chromosome complement and another containing an extra chromosome 21. Which mechanism most likely produced this pattern?

A 46-year-old man has markedly elevated LDL cholesterol from early adulthood. Several members of successive generations are similarly affected. The abnormal allele reduces normal LDL-receptor function despite the presence of a normal allele. Which molecular principle most appropriately explains the disorder?

A genetic disorder is suspected to result from an expanded repetitive DNA region. The laboratory needs to separate DNA fragments according to size and identify fragments containing a particular DNA sequence with a labeled probe. Which method best matches this requirement?

A child with an inherited enzyme deficiency accumulates a metabolic substrate and also lacks an important downstream product. Which sequence best represents the biochemical basis of the disease?

A patient with G6PD deficiency develops hemolysis after exposure to an oxidant drug. This reaction is an example of which concept?

A patient is suspected of having a specific chromosomal deletion. The laboratory wants to use a fluorescently labeled DNA probe that binds directly to the corresponding region within intact nuclei. Which technique is most appropriate?