39 Year 2: Molecular Genetics and Cytogenetics exam questions on INTRODUCTION TO GENETIC DISORDERS AND MUTATIONS MCQs for medical students. Includes MCQs, answe
This MCQ set contains 39 questions on INTRODUCTION TO GENETIC DISORDERS AND MUTATIONS MCQs in the Year 2: Molecular Genetics and Cytogenetics unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.
Correct answer: C – 670
The lifetime frequency of genetic disease is thought to be 670 per 1000 individuals, which is higher than widely appreciated, meaning approximately 67% of people will develop some genetic-related condition.
Correct answer: C – 30,000
Human beings have approximately 30,000 genes, though less than 2% of these actually code for proteins, with more than half being repetitive nucleotide sequences.
Correct answer: A – Less than 2%
Less than 2% of human DNA codes for proteins. More than half of the genome consists of repetitive nucleotide sequences of mysterious function.
Correct answer: D – 99.9%
Individuals share 99.9% of their DNA sequence with each other, with only 0.1% (about 3 million base pairs) accounting for the diversity in the human race.
Correct answer: C – 50%
Approximately 50% of early pregnancy miscarriages have demonstrable chromosomal abnormalities, highlighting the significant impact of genetic disorders on early development.
Correct answer: B – Substitution of a single nucleotide base by a different base
A point mutation is the substitution of a single nucleotide base by a different base, resulting in substitution of an amino acid within a protein, such as in sickle cell anemia.
Correct answer: B – Point mutation
Sickle cell anemia is caused by a point mutation where a single nucleotide substitution leads to the replacement of glutamic acid with valine in the β-globin chain.
Correct answer: B – Insertion or deletion of one or two base pairs altering the reading frame
A frameshift mutation involves insertion or deletion of one or two base pairs that alters the reading frame of the DNA strand, changing all subsequent amino acids in the protein.
Correct answer: C – Trinucleotide repeat mutation
Trinucleotide repeat mutations involve dynamic amplification of a sequence of three nucleotides (often guanine and cytosine), with the degree of amplification increasing at gametogenesis.
Correct answer: C – Fragile X syndrome
Fragile X syndrome is the classic example of a trinucleotide repeat mutation, involving expansion of CGG repeats in the FMR1 gene.
Correct answer: B – Mutant genes, multifactorial inheritance, chromosomal aberrations
The three major categories of genetic disorders are: diseases related to mutant genes of large effect, diseases with multifactorial (polygenic) inheritance, and diseases arising from chromosomal aberrations.
Correct answer: B – Mutations transmitted to progeny causing inherited diseases
Mutations affecting germ cells are transmitted to progeny and cause inherited diseases, unlike somatic mutations which are not transmitted to offspring.
Correct answer: C – Cancers and some congenital malformations
Mutations affecting somatic cells are not transmitted to progeny but can cause cancers and some congenital malformations in the affected individual.
Correct answer: B – Starting with known affected protein to isolate and clone normal gene
Functional cloning starts with a known affected protein (clinical phenotype), then isolates and clones the normal gene, and determines molecular changes affecting the gene.
Correct answer: C – Mapping disease phenotype to chromosome location and cloning DNA from region
Positional cloning involves mapping a disease phenotype to a particular chromosome location, cloning several DNA pieces from the region in vitro, and identifying aberrant proteins from mutated genes.
Correct answer: B – Growth hormone and erythropoietin
Human biologically active agents like soluble TNF receptor, tissue plasminogen activator, growth hormone, and erythropoietin are produced by inserting requisite genes into bacteria or suitable cells in tissue culture.
Correct answer: B – Treating genetic diseases by transfer of somatic cells transfected with normal genes
Gene therapy involves treating genetic diseases by transferring somatic cells that have been transfected with normal genes, though questions remain about whether benefits outweigh risks.
Correct answer: B – Point mutation resulting in amino acid substitution
A missense mutation is a type of point mutation where nucleotide substitution results in a different amino acid being incorporated into the protein, potentially affecting protein function.
Correct answer: B – Point mutation creating premature stop codon
A nonsense mutation is a point mutation that creates a premature stop codon, leading to truncated protein production and usually loss of protein function.
Correct answer: B – Cardiovascular diseases, immunity disorders, cancers
Beyond classic genetic disorders, cardiovascular diseases, disorders of immunity, and cancers are now recognized to have significant genetic components.
Correct answer: B – Multiple genes plus environmental factors
Diseases with multifactorial or polygenic inheritance result from the interaction of multiple genes along with environmental factors, rather than a single gene defect.
Correct answer: B – They are dynamic with amplification increasing at gametogenesis
Trinucleotide repeat mutations are dynamic, meaning the degree of amplification increases during gametogenesis, which can lead to anticipation (worsening severity in successive generations).
Correct answer: B – Epigenetic influences where gene expression depends on parent of origin
Genomic imprinting is an epigenetic phenomenon where the expression of certain genes depends on whether they were inherited from the mother or father, affecting disease transmission.
Correct answer: B – Other category beyond three major types
Diseases resulting from mutations in mitochondrial DNA constitute a separate category beyond the three major categories, with unique maternal inheritance patterns.
Correct answer: B – For both genetic and nongenetic (e.g., infectious) diseases
Molecular probes can be used in diagnosis of both genetic diseases and nongenetic diseases such as infectious diseases, making them versatile diagnostic tools.