Human Genetics & Heredity MCQs 2026

Why does an X-linked recessive disorder like hemophilia predominantly affect males rather than females

1. A Males have only one X chromosome, so a single recessive allele is sufficient to cause the disorder ✓
2. B Females cannot carry the gene for this disorder at all ✓
3. C The disorder only affects Y chromosomes, which only males have ✓
4. D Males are simply more susceptible for unrelated biological reasons ✓

What inherited disorder, caused by a mutation on the X chromosome, impairs normal blood clotting and predominantly affects males

1. A Cystic fibrosis (an autosomal recessive disorder, different inheritance pattern) ✓
2. B Hemophilia ✓
3. C Down syndrome (a chromosomal disorder, different category) ✓
4. D Sickle cell disease (an autosomal recessive disorder, different inheritance pattern) ✓

What is the term for genetic disorders caused by abnormalities in the number or structure of chromosomes

1. A Monogenic disorders (caused by a single gene, a different category) ✓
2. B Polygenic disorders (caused by multiple genes, a different category) ✓
3. C Chromosomal disorders ✓
4. D Multifactorial disorders (caused by combination of genes and environment, a different category) ✓

What is the term for genetic disorders caused by an abnormality in a single gene

1. A Monogenic disorders ✓
2. B Polygenic disorders (caused by multiple genes, a different category) ✓
3. C Chromosomal disorders (caused by abnormal chromosome number/structure, a different category) ✓
4. D Multifactorial disorders (caused by combination of genes and environment, a different category) ✓

In humans, which parent's chromosome determines the biological sex of their child

1. A The mother's (X chromosome only) ✓
2. B The father's (contributes either X or Y) ✓
3. C Both parents equally determine sex through combined contribution ✓
4. D Neither parent; sex is randomly determined independent of chromosomes ✓

If a child inherits brown eye alleles from both parents, and brown is dominant over blue, what genotype do they have for this trait

1. A Heterozygous ✓
2. B Homozygous dominant ✓
3. C Homozygous recessive ✓
4. D Codominant ✓

What is the term for the specific version or form of a gene that determines a particular trait

1. A Chromosome (the broader structure carrying many genes) ✓
2. B Allele ✓
3. C Genotype (relates to the overall genetic makeup, a broader concept) ✓
4. D Phenotype (relates to observable characteristics, a different concept) ✓

What term describes an individual carrying two different alleles for a particular gene, such as one brown-eye allele and one blue-eye allele

1. A Homozygous dominant ✓
2. B Homozygous recessive ✓
3. C Heterozygous ✓
4. D Hemizygous ✓

What famous, historically significant royal family lineage is often cited as an example of hemophilia's spread through European nobility, tracing back to Queen Victoria

1. A The British/European royal houses descended from Queen Victoria ✓
2. B The French Bourbon dynasty (a different royal lineage, not primarily associated with this specific hemophilia case study) ✓
3. C The Spanish Habsburg dynasty (associated with different genetic issues, primarily from inbreeding) ✓
4. D The Russian Romanov dynasty exclusively (though affected, the condition traces back through the broader Victorian lineage, not originating there) ✓

What term describes the phenomenon where one gene's expression masks or influences the expression of a different gene at another location

1. A Pleiotropy (relates to one gene affecting multiple traits, the opposite relationship) ✓
2. B Polygenic inheritance (relates to multiple genes affecting one trait, a different concept) ✓
3. C Codominance (relates to simultaneous allele expression, a different concept) ✓
4. D Epistasis ✓

What term describes the phenomenon where a gene affects multiple, seemingly unrelated traits

1. A Pleiotropy ✓
2. B Polygenic inheritance (relates to multiple genes affecting one trait, the opposite relationship) ✓
3. C Codominance (relates to simultaneous allele expression, a different concept) ✓
4. D Epistasis (relates to one gene masking the effect of another, a different concept) ✓

What is the term for fraternal twins, who develop from two separate eggs fertilized by two separate sperm

1. A Monozygotic twins (develop from a single fertilized egg, a different type) ✓
2. B Dizygotic twins ✓
3. C Conjoined twins (a rare condition where twins remain physically connected, a different concept) ✓
4. D Identical twins (a common name for monozygotic twins, a different type) ✓

What is the term for identical twins, who develop from a single fertilized egg that splits into two separate embryos

1. A Monozygotic twins ✓
2. B Dizygotic twins (develop from two separately fertilized eggs, a different type) ✓
3. C Fraternal twins (a common name for dizygotic twins, a different type) ✓
4. D Conjoined twins (a rare condition where twins remain physically connected, a different concept) ✓

What term describes traits controlled by multiple genes working together, producing a continuous range of possible outcomes, such as human height or skin color

1. A Monogenic traits (controlled by a single gene, a different category) ✓
2. B Polygenic traits ✓
3. C Sex-linked traits (controlled by genes on sex chromosomes specifically, a different, related category) ✓
4. D Codominant traits (relates to simultaneous expression of two alleles, a different concept) ✓

What is the term for treating or preventing disease by directly introducing, altering, or removing genetic material within a patient's cells

1. A Genetic screening (relates to identifying disorders, a different practice) ✓
2. B Genetic counseling (relates to providing advisory guidance, a different practice) ✓
3. C Gene therapy ✓
4. D Selective breeding (a broader agricultural/animal breeding concept, a different practice) ✓

What is the term for the professional guidance provided to individuals or families regarding genetic risks, testing options, and disease implications

1. A Genetic screening (a related, but distinct practice, focused on the testing itself) ✓
2. B Genetic counseling ✓
3. C Genetic engineering (relates to directly modifying genes, a different practice) ✓
4. D Gene therapy (relates to treating disorders by altering genes directly, a different practice) ✓

What is the term for the branch of medicine and testing specifically focused on identifying genetic disorders before or shortly after birth

1. A Genetic screening/testing ✓
2. B Genetic engineering (relates to directly modifying genes, a different practice) ✓
3. C Genetic counseling (a related, but distinct practice, focused on advising individuals/families about genetic risk) ✓
4. D Gene therapy (relates to treating disorders by altering genes directly, a different practice) ✓

What inherited disorder causes red blood cells to take on an abnormal crescent shape, more common in populations of African descent

1. A Cystic fibrosis (more common in populations of European descent, different disorder) ✓
2. B Thalassemia (a related, but distinct disorder, more common in different populations) ✓
3. C Sickle cell disease ✓
4. D Tay-Sachs disease (a different inherited disorder, with different symptoms/population prevalence) ✓

What inherited disorder causes thick, sticky mucus buildup, particularly affecting the lungs and digestive system, more common in populations of European descent

1. A Cystic fibrosis ✓
2. B Thalassemia (a different inherited disorder, more common in different populations) ✓
3. C Sickle cell disease (a different inherited disorder, more common in different populations) ✓
4. D Tay-Sachs disease (a different inherited disorder, with different symptoms/population prevalence) ✓

What inherited disorder, common in some Mediterranean and Asian populations, results in abnormal hemoglobin production

1. A Cystic fibrosis (a different inherited disorder, more common in populations of European descent) ✓
2. B Thalassemia ✓
3. C Hemophilia (a different inherited disorder, with a different inheritance pattern) ✓
4. D Huntington's disease (a different inherited disorder, dominant rather than recessive, with different symptoms) ✓

What term describes a female who carries one copy of a recessive X-linked disorder allele but does not show symptoms, due to having a second, normal X chromosome

1. A Carrier ✓
2. B Affected individual (would show symptoms, a different status) ✓
3. C Homozygous recessive (would require two copies of the allele, a different genetic status) ✓
4. D Hemizygous (a term specifically describing males with only one X chromosome, a different concept) ✓