Genetic Disorders MCQ Examination | MCQ Quiz | OmpathStudy Kenya

Question 1

A couple has a child with an autosomal recessive disorder. Neither parent is affected. What is the probability that their next child will be affected?

Accepted Answer

25% — In autosomal recessive inheritance, two carrier parents have a 25% chance with each pregnancy of having an affected child (homozygous recessive), 50% chance of a carrier, and 25% chance of being unaffected and not a carrier.

Question 2

An estimated 50% of early pregnancy miscarriages have which underlying cause?

Accepted Answer

Demonstrable chromosomal abnormalities — Approximately 50% of early pregnancy miscarriages are associated with demonstrable chromosomal abnormalities, highlighting the importance of genomic integrity in fetal development.

Question 3

What percentage of human DNA codes for proteins?

Accepted Answer

Less than 2% — Less than 2% of human DNA actually codes for proteins. More than half consists of repetitive nucleotide sequences whose functions are not fully understood.

Question 4

A patient has a genetic condition that shows different severity among affected family members despite having the same mutation. This phenomenon is called

Accepted Answer

Variable expressivity — Variable expressivity occurs when a trait is seen in all individuals with the mutation but is expressed differently in terms of severity or manifestation. Reduced penetrance refers to some individuals not showing the trait at all.

Question 5

Sickle cell anemia results from which type of mutation?

Accepted Answer

Point mutation (non-conservative missens — Sickle cell anemia results from a single nucleotide substitution (point mutation) that causes a non-conservative missense mutation, replacing glutamic acid with valine in the beta-globin chain.

Question 6

Which approach to understanding genetic disease starts with identifying a known affected protein, then isolating the normal gene?

Accepted Answer

Functional cloning — Functional cloning (classic approach) begins with a known affected protein from the clinical phenotype, then isolates and clones the normal gene before determining molecular changes.

Question 7

A mutation that changes an amino acid codon to a chain terminator is classified as

Accepted Answer

Nonsense mutation — Nonsense mutations convert an amino acid codon into a stop codon (chain terminator), resulting in premature termination of protein synthesis and usually a non-functional truncated protein.

Question 8

How many deleterious genes does the average person carry?

Accepted Answer

5-8 — It is estimated that every person carries 5 to 8 deleterious genes, most being recessive. About 80% are familial and the remainder are acquired de novo.

Question 9

In X-linked recessive disorders, an affected male will

Accepted Answer

Not transmit to sons; daughters will be carriers — In X-linked recessive disorders, affected males pass their Y chromosome to sons (who are unaffected) and their X chromosome to daughters (who become carriers).

Question 10

Fragile X syndrome is caused by which type of mutation?

Accepted Answer

Trinucleotide repeat mutation — Fragile X syndrome results from dynamic amplification of a trinucleotide repeat sequence (typically CGG repeats), with the degree of amplification increasing during gametogenesis.

Question 11

What percentage of individuals under 25 years develop a serious disease with significant genetic component?

Accepted Answer

25% — Approximately 5% of individuals under 25 years develop a serious disease with a significant genetic component, demonstrating the considerable impact of genetic disorders in young populations.

Question 12

A single mutant gene leading to multiple, seemingly unrelated effects is an example of

Accepted Answer

Pleiotropy — Pleiotropy occurs when a single mutant gene leads to many different end effects, affecting multiple organ systems or producing various manifestations from one genetic defect.

Question 13

Which category represents the largest group of Mendelian disorders?

Accepted Answer

Autosomal recessive — Autosomal recessive disorders constitute the largest category of Mendelian disorders and include almost all inborn errors of metabolism.

Question 14

Mutations in promoter and enhancer sequences primarily affect

Accepted Answer

Binding of transcription factors and gene transcription — Mutations in regulatory sequences (promoters and enhancers) interfere with binding of transcription factors, leading to reduced or absent transcription of the gene, as seen in some hereditary hemolytic anemias.

Question 15

In 2020, how many deaths worldwide were attributed to cancer?

Accepted Answer

10 million — In 2020, there were approximately 10 million cancer deaths globally (representing 1 in 6 deaths), up from 6 million in 2000, showing an increasing cancer burden.

Question 16

A deletion or insertion of two base pairs in a coding sequence would most likely result in

Accepted Answer

Frameshift mutation — Insertion or deletion of one or two base pairs (not divisible by 3) causes a frameshift mutation, altering the reading frame and typically producing a non-functional protein.

Question 17

When mutations at several different genetic loci produce the same clinical trait, this is called

Accepted Answer

Genetic heterogeneity — Genetic heterogeneity occurs when mutations at different genetic loci can produce the same phenotype or disease trait, explaining why the same disease can result from different genetic defects.

Question 18

Which inheritance pattern typically shows that the trait does not affect parents but may affect siblings?

Accepted Answer

Autosomal recessive — Autosomal recessive inheritance typically shows unaffected parents (both carriers) with affected siblings, as the trait requires two copies of the mutant allele to manifest.

Question 19

Complete penetrance is most commonly seen in

Accepted Answer

Autosomal recessive disorders — Complete penetrance is common in autosomal recessive disorders, where expression of the defect tends to be more uniform than in autosomal dominant disorders which often show variable penetrance.

Question 20

The lifetime frequency of genetic disease is estimated to be

Accepted Answer

670 per 1000 — The lifetime frequency of genetic disease is thought to be approximately 670 per 1000, which is higher than widely appreciated, including cardiovascular diseases, immune disorders, and cancers with genetic components.

Question 21

Individuals share what percentage of their DNA sequence with other humans?

Accepted Answer

99.9% — Humans share 99.9% of their DNA sequence, with only 0.1% (about 3 million base pairs) accounting for genetic diversity among individuals in the human race.

Question 22

A frameshift mutation would NOT occur with an insertion or deletion of

Accepted Answer

3 base pairs — Insertions or deletions of 3 base pairs (or multiples of 3) do not cause frameshift mutations because they maintain the reading frame, though they result in abnormal proteins missing or gaining amino acids.

Question 23

In autosomal dominant disorders, de novo mutations are more commonly associated with

Accepted Answer

Older fathers — De novo mutations in autosomal dominant disorders are more frequently associated with relatively older fathers, as mutations accumulate in spermatogonial cells over time.

Question 24

Which statement about autosomal recessive disorders is INCORRECT?

Accepted Answer

Parents are usually affected — In autosomal recessive disorders, parents are typically NOT affected but are carriers. The trait manifests in children who inherit two mutant alleles.

Question 25

Positional cloning approach involves

Accepted Answer

Mapping disease phenotype to chromosome location first — Positional cloning (candidate gene approach) starts by mapping the disease phenotype to a particular chromosome location, then cloning DNA pieces from that region to identify aberrant proteins.

Question 26

Conservative missense mutations differ from non-conservative ones in that they

Accepted Answer

Substitute chemically similar amino acids — Conservative missense mutations substitute an amino acid with another that has similar chemical properties, potentially having less severe effects than non-conservative mutations that substitute chemically different amino acids.

Question 27

Vitamin D-resistant rickets represents which unusual inheritance pattern?

Accepted Answer

X-linked dominant — Vitamin D-resistant rickets is one of the few X-linked dominant conditions, making it an exception to the rule that almost all X-linked disorders are recessive.

Question 28

Gene therapy aims to treat genetic diseases by

Accepted Answer

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.

Question 29

In Kenya (2018), cancer was which leading cause of death?

Accepted Answer

3rd — In Kenya in 2018, cancer was the 3rd leading cause of death, with 47,887 new cases and 32,987 deaths reported, showing a significant increase from 2012 figures.

Question 30

Mutations affecting somatic cells result in

Accepted Answer

Cancers and some congenital malformations — Somatic cell mutations are not transmitted to progeny but can result in cancers and some congenital malformations in the affected individual.

Question 31

The term "reduced penetrance" means

Accepted Answer

Some percentage show the trait, others are phenotypically normal despite having the mutation — Reduced penetrance refers to the phenomenon where a certain percentage of individuals with a mutation are affected while others remain phenotypically normal despite carrying the mutation.

Question 32

Which biologically active agent can be produced by inserting requisite genes into bacteria?

Accepted Answer

Erythropoietin — Human biologically active agents like erythropoietin, growth hormone, tissue plasminogen activator, and soluble TNF receptor can be produced by inserting genes into bacteria or cultured cells.

Question 33

Approximately how many genes do humans have?

Accepted Answer

30,000 — Human beings have approximately 30,000 genes, though less than 2% of total DNA codes for proteins, with much of the genome consisting of repetitive sequences.

Question 34

In autosomal dominant inheritance, both males and females

Accepted Answer

Can be affected and can transmit the disorder — Autosomal dominant disorders affect both males and females equally, and both sexes can transmit the disorder to their offspring, requiring only one copy of the mutant allele.

Question 35

Trinucleotide repeat mutations are described as "dynamic" because

Accepted Answer

The degree of amplification increases during gametogenesis — Trinucleotide repeat mutations are dynamic because the degree of amplification (expansion) of the repeat sequence increases during gametogenesis, often leading to more severe disease in successive generations (anticipation).

Question 36

Which category of genetic disorders involves visible structural changes in chromosomes?

Accepted Answer

Chromosome mutations — Chromosome mutations involve rearrangement of genetic material resulting in visible structural changes in chromosomes, distinct from gene mutations or whole chromosome gains/losses.

Question 37

A mutation in an enhancer sequence would most likely affect

Accepted Answer

Gene transcription levels — Enhancer sequences are regulatory elements that increase transcription. Mutations in enhancers affect the level of gene transcription by interfering with transcription factor binding.

Question 38

Monosomies and trisomies are examples of

Accepted Answer

Genome mutations — Monosomies (loss of a chromosome) and trisomies (gain of a chromosome) are genome mutations involving the loss or gain of whole chromosomes.

Question 39

Which mechanism is NOT typically involved in autosomal dominant disorders?

Accepted Answer

Requirement for two mutant alleles — Autosomal dominant disorders manifest with only one mutant allele (heterozygous state). Requiring two mutant alleles is characteristic of recessive disorders.

Question 40

The concept of delayed onset is particularly characteristic of

Accepted Answer

Many autosomal dominant disorders — Many autosomal dominant conditions have delayed onset, manifesting in adulthood rather than early in life, which is an important feature distinguishing them from many recessive disorders.

Question 41

What percentage of deleterious genes carried by individuals are familial versus de novo?

Accepted Answer

80% familial, 20% de novo — Of the 5-8 deleterious genes carried by each person, approximately 80% are familial (inherited) and the remainder (20%) are acquired de novo.

Question 42

Molecular probes in disease diagnosis can be used for

Accepted Answer

Both genetic and non-genetic diseases including infections — Molecular probes are used in diagnosis of both genetic diseases and non-genetic diseases, including infectious diseases, making them versatile diagnostic tools.

Question 43

In which type of disorder would consanguinity most likely increase disease prevalence?

Accepted Answer

Autosomal recessive — Consanguinity (marriage between related individuals) significantly increases the risk of autosomal recessive disorders because related individuals are more likely to carry the same recessive mutations.

Question 44

A silent mutation would most likely result from

Accepted Answer

Nucleotide change that doesn't alter amino acid due to genetic code degeneracy — Silent mutations are nucleotide substitutions that don't change the amino acid due to the degeneracy of the genetic code (multiple codons for same amino acid), having no effect on the protein.

Question 45

Almost all inborn errors of metabolism follow which inheritance pattern?

Accepted Answer

Autosomal recessive — Almost all inborn errors of metabolism are autosomal recessive disorders, where enzyme deficiencies manifest only in the homozygous recessive state.

Question 46

Between 2000 and 2020, global new cancer cases increased by approximately

Accepted Answer

8 million — New cancer cases increased from 10 million in 2000 to 18.1 million in 2020, representing an increase of approximately 8 million cases, highlighting the growing cancer burden globally.

Question 47

Which biochemical/molecular basis is NOT listed as a mechanism for Mendelian disorders?

Accepted Answer

Prion protein misfolding — The listed mechanisms include enzyme defects, receptor defects, transport defects, structural protein alterations, hemostasis defects, and growth regulation defects. Prion diseases are not typical Mendelian disorders.

Question 48

Gene expression in Mendelian disorders may be

Accepted Answer

Dominant, recessive, or co-dominant — Gene expression in Mendelian disorders can be dominant (one mutant allele sufficient), recessive (two mutant alleles needed), or co-dominant (both alleles expressed).

Question 49

A patient has a disorder that shows genetic heterogeneity. This means

Accepted Answer

Multiple genes can cause the same disease — Genetic heterogeneity means that mutations at several different genetic loci can produce the same trait or disease phenotype, explaining why clinically similar diseases can have different genetic causes.

Question 50

The main difference between benign and malignant neoplasms is

Accepted Answer

Ability to invade and metastasize — The fundamental difference is that malignant neoplasms can invade adjacent tissues and metastasize to distant sites, while benign tumors remain localized despite potentially growing large.

Genetic Disorders MCQ Examination | MCQ Quiz | OmpathStudy Kenya

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