Principles of Inheritance and Variation MCQ

Principles of Inheritance and Variation MCQ. Test your understanding of Class 12 Inheritance & Variation with MCQs on Mendel’s work, gene linkage, sex linkage, mutation & genetic diseases.

Principles of Inheritance and Variation MCQ – Mock Online Test

Question 1: What is the term for the process by which characters are passed on from parent to progeny?

A. Variation
B. Inheritance
C. Mutation
D. Selection

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Correct Answer: B. Inheritance. It is the basis of heredity.

Question 2: Which of the following is NOT a contrasting trait in pea plants that Mendel studied?

A. Tall/dwarf plants
B. Yellow/green seeds
C. Smooth/wrinkled seeds
D. Purple/white flowers

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Correct Answer: C. Smooth/wrinkled seeds. While Mendel did study seed shape, he focused on round/wrinkled, not smooth/wrinkled.

Question 3: What type of plants did Mendel use in his hybridization experiments?

A. Tomato plants
B. Pea plants
C. Rose plants
D. Corn plants

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Correct Answer: B. Pea plants. They were ideal due to their distinct traits and ease of controlled pollination.

Question 4: What is the term for the degree to which progeny differ from their parents?

A. Inheritance
B. Variation
C. Dominance
D. Segregation

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Correct Answer: B. Variation. It contributes to the diversity within a species.

Question 5: Why did Mendel select pea plants for his experiments?

A. They were easy to grow.
B. They had a short generation time.
C. They exhibited contrasting traits.
D. All of the above.

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Correct Answer: D. All of the above. These characteristics made pea plants suitable for genetic studies.

Question 6: What is a true-breeding line?

A. A line that shows stable trait inheritance for several generations.
B. A line that produces offspring with a mix of traits.
C. A line that cannot self-pollinate.
D. A line that is always heterozygous.

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Correct Answer: A. A line that shows stable trait inheritance for several generations. This is achieved through continuous self-pollination.

Question 7: Which of the following did Mendel NOT introduce to the field of biology?

A. Statistical analysis
B. Mathematical logic
C. Microscopic observation of chromosomes
D. Laws of inheritance

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Correct Answer: C. Microscopic observation of chromosomes. Chromosome studies came after Mendel’s work.

Question 8: What is the difference between inheritance and variation?

A. Inheritance is the passing of traits, while variation is the differences in those traits.
B. Inheritance is caused by mutations, while variation is caused by the environment.
C. Inheritance is random, while variation is predictable.
D. There is no difference; they are the same concept.

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Correct Answer: A. Inheritance is the passing of traits, while variation is the differences in those traits.

Question 9: Why are contrasting traits important in genetic studies?

A. They make it easier to observe patterns of inheritance.
B. They are more common than other types of traits.
C. They are only found in pea plants.
D. They are always dominant.

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Correct Answer: A. They make it easier to observe patterns of inheritance.

Question 10: How did Mendel ensure that his pea plants were true-breeding?

A. He cross-pollinated them with different varieties.
B. He grew them in different environments.
C. He allowed them to self-pollinate for several generations.
D. He treated them with chemicals.

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Correct Answer: C. He allowed them to self-pollinate for several generations.

Question 11: What is the significance of Mendel’s work?

A. He discovered the basic principles of inheritance.
B. He developed the theory of evolution.
C. He invented the microscope.
D. He discovered DNA.

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Correct Answer: A. He discovered the basic principles of inheritance.

Question 12: What is the expected phenotypic ratio in the F2 generation of a monohybrid cross?

A. 1:1
B. 2:1
C. 3:1
D. 4:1

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Correct Answer: C. 3:1 This ratio represents the dominant to recessive phenotype.

Question 13: What is the purpose of a test cross?

A. To determine the genotype of an individual with a dominant phenotype.
B. To determine the phenotype of an individual with a recessive genotype.
C. To create a new hybrid variety.
D. To study the effects of the environment on traits.

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Correct Answer: A. To determine the genotype of an individual with a dominant phenotype.

Question 14: Which of the following is an example of a recessive trait in humans?

A. Brown eyes
B. Attached earlobes
C. Freckles
D. Cystic fibrosis

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Correct Answer: D. Cystic fibrosis. This genetic disorder is only expressed when an individual inherits two recessive alleles.

Question 15: What is the law of segregation?

A. Alleles of a gene separate from each other during gamete formation.
B. One allele always dominates the other.
C. Genes located on the same chromosome are always inherited together.
D. The environment determines which traits are expressed.

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Correct Answer: A. Alleles of a gene separate from each other during gamete formation.

Question 16: What is a monohybrid cross?

A. A cross between two individuals that differ in one character.
B. A cross between two individuals that differ in two characters.
C. A cross between two individuals that are identical for all characters.
D. A cross between two different species.

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Correct Answer: A. A cross between two individuals that differ in one character.

Question 17: What is the F1 generation?

A. The first generation of offspring from a cross.
B. The second generation of offspring from a cross.
C. The parents in a cross.
D. The offspring of a test cross.

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Correct Answer: A. The first generation of offspring from a cross.

Question 18: What is the F2 generation?

A. The first generation of offspring from a cross.
B. The second generation of offspring from a cross.
C. The parents in a cross.
D. The offspring of a test cross.

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Correct Answer: B. The second generation of offspring from a cross.

Question 19: What is a dominant trait?

A. The trait that is expressed in the F1 generation.
B. The trait that is not expressed in the F1 generation.
C. The trait that is only expressed in the homozygous condition.
D. The trait that is only expressed in the heterozygous condition.

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Correct Answer: A. The trait that is expressed in the F1 generation.

Question 20: What is a recessive trait?

A. The trait that is expressed in the F1 generation.
B. The trait that is not expressed in the F1 generation but may reappear in the F2 generation.
C. The trait that is only expressed in the homozygous condition.
D. The trait that is only expressed in the heterozygous condition.

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Correct Answer: B. The trait that is not expressed in the F1 generation but may reappear in the F2 generation.

Question 21: What are genes?

A. The observable characteristics of an organism.
B. The units of inheritance, containing information to express a particular trait.
C. The different forms of a trait.
D. Environmental factors that affect traits.

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Correct Answer: B. The units of inheritance, containing information to express a particular trait.

Question 22: What are alleles?

A. The observable characteristics of an organism.
B. The units of inheritance, containing information to express a particular trait.
C. Different forms of the same gene, responsible for contrasting traits.
D. Environmental factors that affect traits.

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Correct Answer: C. Different forms of the same gene, responsible for contrasting traits.

Question 23: What is a genotype?

A. The genetic makeup of an organism.
B. The observable characteristics of an organism.
C. The physical location of a gene on a chromosome.
D. The process of gamete formation.

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Correct Answer: A. The genetic makeup of an organism.

Question 24: What is a phenotype?

A. The genetic makeup of an organism.
B. The observable characteristics of an organism.
C. The physical location of a gene on a chromosome.
D. The process of gamete formation.

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Correct Answer: B. The observable characteristics of an organism.

Question 25: What does it mean for an organism to be homozygous?

A. Having two identical alleles for a gene.
B. Having two different alleles for a gene.
C. Having only one allele for a gene.
D. Having no alleles for a gene.

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Correct Answer: A. Having two identical alleles for a gene.

Question 26: What does it mean for an organism to be heterozygous?

A. Having two identical alleles for a gene.
B. Having two different alleles for a gene.
C. Having only one allele for a gene.
D. Having no alleles for a gene.

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Correct Answer: B. Having two different alleles for a gene.

Question 27: What is the purpose of a Punnett square?

A. To visualize the possible genotypes and phenotypes of offspring from a cross.
B. To determine the actual outcome of a cross.
C. To show the physical location of genes on chromosomes.
D. To illustrate the process of meiosis.

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Correct Answer: A. To visualize the possible genotypes and phenotypes of offspring from a cross.

Question 28: What is a test cross used for?

A. To determine the genotype of an individual with a dominant phenotype.
B. To determine the phenotype of an individual with a recessive genotype.
C. To identify new mutations.
D. To study the effects of the environment on traits.

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Correct Answer: A. To determine the genotype of an individual with a dominant phenotype.

Question 29: What is the law of dominance?

A. One allele always dominates the other.
B. Alleles of a gene separate from each other during gamete formation.
C. Genes located on the same chromosome are always inherited together.
D. The environment determines which traits are expressed.

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Correct Answer: A. One allele always dominates the other.

Question 30: In a monohybrid cross between a homozygous dominant (TT) and a homozygous recessive (tt) individual, what is the expected genotype of the F1 offspring?

A. All Tt
B. All TT
C. All tt
D. Half TT and half tt

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Correct Answer: A. All Tt. The offspring inherit one ‘T’ allele from the dominant parent and one ‘t’ allele from the recessive parent.

Question 31: In a monohybrid cross, if the F1 generation exhibits only the dominant trait, what does this indicate about the parents?

A. Both parents were homozygous dominant.
B. Both parents were homozygous recessive.
C. One parent was homozygous dominant, and the other was homozygous recessive.
D. Both parents were heterozygous.

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Correct Answer: C. One parent was homozygous dominant, and the other was homozygous recessive.

Question 32: In a monohybrid cross, if the F2 generation exhibits a 3:1 ratio of dominant to recessive phenotypes, what does this indicate about the F1 generation?

A. The F1 generation was homozygous dominant.
B. The F1 generation was homozygous recessive.
C. The F1 generation was heterozygous.
D. The F1 generation had a mix of homozygous dominant and homozygous recessive individuals.

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Correct Answer: C. The F1 generation was heterozygous.

Question 33: What is the expected phenotypic ratio in the F2 generation of a monohybrid cross where incomplete dominance is observed?

A. 3:1
B. 1:2:1
C. 9:3:3:1
D. 1:1

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Correct Answer: B. 1:2:1. This ratio reflects the blending of traits seen in incomplete dominance.

Question 34: What is an example of a trait that exhibits incomplete dominance?

A. Flower color in snapdragons
B. Seed shape in pea plants
C. Human blood type
D. Human height

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Correct Answer: A. Flower color in snapdragons. A cross between red and white snapdragons produces pink offspring.

Question 35: What is co-dominance?

A. When both alleles in a heterozygote are fully expressed.
B. When one allele is completely dominant over the other.
C. When the phenotype of the heterozygote is intermediate between the two homozygotes.
D. When the environment determines the expression of a trait.

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Correct Answer: A. When both alleles in a heterozygote are fully expressed.

Question 36: What is an example of a trait that exhibits co-dominance?

A. Flower color in snapdragons
B. Seed shape in pea plants
C. Human blood type
D. Human height

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Correct Answer: C. Human blood type. The AB blood type is a result of both A and B alleles being expressed.

Question 37: What is the difference between incomplete dominance and co-dominance?

A. In incomplete dominance, the heterozygote has a blended phenotype; in co-dominance, both alleles are distinctly expressed.
B. Incomplete dominance involves multiple alleles; co-dominance involves only two alleles.
C. Incomplete dominance is only observed in plants; co-dominance is only observed in animals.
D. There is no difference; they are the same concept.

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Correct Answer: A. In incomplete dominance, the heterozygote has a blended phenotype; in co-dominance, both alleles are distinctly expressed.

Question 38: What is the purpose of a test cross?

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Correct Answer: A. To determine the genotype of an individual with a dominant phenotype.

Question 39: In a test cross, an individual with a dominant phenotype is crossed with which of the following?

A. A homozygous dominant individual
B. A heterozygous individual
C. A homozygous recessive individual
D. Any of the above

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Correct Answer: C. A homozygous recessive individual.

Question 40: If the offspring of a test cross all exhibit the dominant phenotype, what does this indicate about the genotype of the unknown parent?

A. It is homozygous dominant.
B. It is heterozygous.
C. It is homozygous recessive.
D. It cannot be determined from this information.

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Correct Answer: A. It is homozygous dominant.

Question 41: If the offspring of a test cross exhibit a 1:1 ratio of dominant to recessive phenotypes, what does this indicate about the genotype of the unknown parent?

A. It is homozygous dominant.
B. It is heterozygous.
C. It is homozygous recessive.
D. It cannot be determined from this information.

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Correct Answer: B. It is heterozygous.

Question 42: What is the role of meiosis in the law of segregation?

A. Meiosis separates homologous chromosomes, which carry the alleles, into different gametes.
B. Meiosis causes mutations that create new alleles.
C. Meiosis combines alleles from different parents to create offspring.
D. Meiosis determines the sex of the offspring.

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Correct Answer: A. Meiosis separates homologous chromosomes, which carry the alleles, into different gametes.

Question 43: How does the law of segregation contribute to genetic variation?

A. It ensures that each gamete receives a random combination of alleles.
B. It prevents mutations from occurring.
C. It determines the sex of the offspring.
D. It controls the expression of dominant and recessive traits.

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Correct Answer: A. It ensures that each gamete receives a random combination of alleles.

Question 44: What is the relationship between genes and alleles?

A. Genes are different forms of alleles.
B. Alleles are different forms of genes.
C. Genes and alleles are the same thing.
D. Genes are located on chromosomes, while alleles are located on proteins.

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Correct Answer: B. Alleles are different forms of genes.

Question 45: How do dominant and recessive alleles interact in a heterozygous individual?

A. The dominant allele is expressed, while the recessive allele is masked.
B. The recessive allele is expressed, while the dominant allele is masked.
C. Both alleles are expressed equally.
D. Neither allele is expressed.

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Correct Answer: A. The dominant allele is expressed, while the recessive allele is masked.

Question 46: How can a recessive trait be expressed?

A. Only in a homozygous recessive individual.
B. Only in a heterozygous individual.
C. In both homozygous and heterozygous individuals.
D. Never, recessive traits are always masked.

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Correct Answer: A. Only in a homozygous recessive individual.

Question 47: What is a dihybrid cross?

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Correct Answer: B. A cross between two individuals that differ in two characters.

Question 48: What is the law of independent assortment?

A. Alleles of a gene separate from each other during gamete formation.
B. One allele always dominates the other.
C. The segregation of one pair of characters is independent of the other pair.
D. The environment determines which traits are expressed.

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Correct Answer: C. The segregation of one pair of characters is independent of the other pair.

Question 49: What is the expected phenotypic ratio in the F2 generation of a dihybrid cross?

A. 3:1
B. 1:2:1
C. 9:3:3:1
D. 1:1

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Correct Answer: C. 9:3:3:1. This ratio reflects the independent assortment of two different traits.

Question 50: In a dihybrid cross, what does the law of independent assortment imply about the inheritance of two different traits?

A. The inheritance of one trait influences the inheritance of the other trait.
B. The inheritance of one trait does not influence the inheritance of the other trait.
C. The two traits are always inherited together.
D. The two traits are always inherited separately.

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Correct Answer: B. The inheritance of one trait does not influence the inheritance of the other trait.

Question 51: What is the chromosomal theory of inheritance?

A. Genes are located on chromosomes.
B. Chromosomes are made of DNA.
C. The environment determines which traits are expresseD.
D. Traits are passed from parents to offspring through the cytoplasm.

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Correct Answer: A. Genes are located on chromosomes.

Question 52: How does the behavior of chromosomes during meiosis support Mendel’s laws?

A. Chromosomes segregate independently during meiosis, just like alleles.
B. Chromosomes blend together during meiosis, just like alleles.
C. Chromosomes are not involved in the inheritance of traits.
D. Chromosomes determine the sex of the offspring.

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Correct Answer: A. Chromosomes segregate independently during meiosis, just like alleles.

Question 53: What is linkage?

A. The physical association of genes on a chromosome.
B. The separation of alleles during gamete formation.
C. The blending of traits in incomplete dominance.
D. The expression of both alleles in co-dominance.

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Correct Answer: A. The physical association of genes on a chromosome.

Question 54: What is recombination?

A. The generation of non-parental gene combinations.
B. The formation of parental gene combinations.
C. The exchange of genetic material between sister chromatids.
D. The mutation of a gene.

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Correct Answer: A. The generation of non-parental gene combinations.

Question 55: How does linkage affect the inheritance of genes?

A. Linked genes are always inherited together.
B. Linked genes are never inherited together.
C. Linked genes are more likely to be inherited together.
D. Linkage has no effect on the inheritance of genes.

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Correct Answer: C. Linked genes are more likely to be inherited together.

Question 56: How does recombination affect the inheritance of genes?

A. Recombination increases the number of parental gene combinations.
B. Recombination increases the number of non-parental gene combinations.
C. Recombination prevents the inheritance of linked genes.
D. Recombination has no effect on the inheritance of genes.

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Correct Answer: B. Recombination increases the number of non-parental gene combinations.

Question 57: What is a linkage map?

A. A map showing the physical location of genes on a chromosome.
B. A map showing the evolutionary relationships between different species.
C. A map showing the inheritance patterns of traits in a family.
D. A map showing the distribution of alleles in a population.

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Correct Answer: A. A map showing the physical location of genes on a chromosome.

Question 58: How are linkage maps constructed?

A. By analyzing the frequency of recombination between genes.
B. By sequencing the DNA of an organism.
C. By observing the behavior of chromosomes during meiosis.
D. By studying the inheritance patterns of traits in a family.

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Correct Answer: A. By analyzing the frequency of recombination between genes.

Question 59: What is the significance of linkage maps?

A. They provide information about the relative distances between genes on a chromosome.
B. They can be used to predict the outcome of crosses.
C. They can be used to identify genes that cause diseases.
D. All of the above.

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Correct Answer: D. All of the above.

Question 60: What is the relationship between linkage and recombination?

A. Linkage increases the frequency of recombination.
B. Linkage decreases the frequency of recombination.
C. Linkage and recombination are independent of each other.
D. Linkage and recombination are the same thing.

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Correct Answer: B. Linkage decreases the frequency of recombination.

Question 61: What are polygenic traits?

A. Traits controlled by a single gene.
B. Traits controlled by two genes.
C. Traits controlled by three or more genes.
D. Traits that are not influenced by genes.

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Correct Answer: C. Traits controlled by three or Mmore genes.

Question 62: What is the additive effect in polygenic inheritance?

A. Each allele contributes equally to the phenotype.
B. One allele dominates all the others.
C. The environment determines the expression of the trait.
D. The trait is only expressed in the homozygous condition.

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Correct Answer: A. Each allele contributes equally to the phenotype.

Question 63: How does the environment influence polygenic traits?

A. The environment does not affect polygenic traits.
B. The environment can affect the expression of polygenic traits.
C. The environment determines the genotype of an individual.
D. The environment causes mutations that create new alleles.

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Correct Answer: B. The environment can affect the expression of polygenic traits.

Question 64: What is an example of a polygenic trait in humans?

A. Blood type
B. Seed shape in pea plants
C. Skin color
D. Eye color

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Correct Answer: C. Skin color. Human skin color is influenced by multiple genes and the environment.

Question 65: What is the difference between polygenic inheritance and Mendelian inheritance?

A. Polygenic inheritance involves multiple genes; Mendelian inheritance involves a single gene.
B. Polygenic inheritance is not influenced by the environment; Mendelian inheritance is influenced by the environment.
C. Polygenic inheritance results in continuous variation; Mendelian inheritance results in discrete variation.
D. Both A and C.

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Correct Answer: D. Both A and C.

Question 66: What is pleiotropy?

A. When one gene affects multiple traits.
B. When multiple genes affect one trait.
C. When the environment determines the expression of a trait.
D. When a mutation occurs in a gene.

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Correct Answer: A. When one gene affects multiple traits.

Question 67: What is a pleiotropic gene?

A. A gene that is only expressed in the homozygous condition.
B. A gene that is only expressed in the heterozygous condition.
C. A gene that affects multiple traits.
D. A gene that is not influenced by the environment.

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Correct Answer: C. A gene that affects multiple traits.

Question 68: How does a pleiotropic gene affect multiple traits?

A. By coding for a protein that is involved in multiple metabolic pathways.
B. By being located on the sex chromosomes.
C. By being influenced by the environment.
D. By mutating at a high frequency.

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Correct Answer: A. By coding for a protein that is involved in multiple metabolic pathways.

Question 69: What is an example of a pleiotropic gene in humans?

A. The gene that controls blood type.
B. The gene that controls seed shape in pea plants.
C. The gene that causes phenylketonuria.
D. The gene that causes Down’s syndrome.

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Correct Answer: C. The gene that causes phenylketonuria. This gene affects mental development, hair color, and skin pigmentation.

Question 70: What is the significance of pleiotropy?

A. It can explain how a single mutation can have multiple effects on an organism.
B. It can help us understand the relationship between genes and traits.
C. It can provide insights into the evolution of complex traits.
D. All of the above.

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Correct Answer: D. All of the above.

Question 71: What are sex chromosomes?

A. Chromosomes that determine the sex of an organism.
B. Chromosomes that are the same in both sexes.
C. Chromosomes that carry only recessive alleles.
D. Chromosomes that are not involved in inheritance.

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Correct Answer: A. Chromosomes that determine the sex of an organism.

Question 72: What are autosomes?

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Correct Answer: B. Chromosomes that are the same in both sexes.

Question 73: What is the XO type of sex determination?

A. Females have two X chromosomes, males have one.
B. Females have two X chromosomes, males have one X and one Y.
C. Females have one Z and one W chromosome, males have two Z chromosomes.
D. Females have one X and one Y chromosome, males have two X chromosomes.

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Correct Answer: A. Females have two X chromosomes, males have one.

Question 74: What is the XY type of sex determination?

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Correct Answer: B. Females have two X chromosomes, males have one X and one Y.

Question 75: What is the ZW type of sex determination?

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Correct Answer: C. Females have one Z and one W chromosome, males have two Z chromosomes.

Question 76: What type of sex determination is found in humans?

A. XO type
B. XY type
C. ZW type
D. None of the above

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Correct Answer: B. XY type.

Question 77: What type of sex determination is found in honey bees?

A. XO type
B. XY type
C. ZW type
D. Haplodiploid system

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Correct Answer: D. Haplodiploid system.

Question 78: In humans, which parent determines the sex of the offspring?

A. The mother
B. The father
C. Both parents equally
D. It is random

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Correct Answer: B. The father. The sex of the offspring depends on whether the sperm carries an X or a Y chromosome.

Question 79: In honey bees, how are males produced?

A. From fertilized eggs
B. From unfertilized eggs
C. From a combination of fertilized and unfertilized eggs
D. None of the above

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Correct Answer: B. From unfertilized eggs.

Question 80: What is the difference between male heterogamety and female heterogamety?

A. In male heterogamety, the male produces two types of gametes; in female heterogamety, the female produces two types of gametes.
B. Male heterogamety is found in humans; female heterogamety is found in birds.
C. Male heterogamety results in an equal number of males and females; female heterogamety results in more females than males.
D. Both A and B.

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Correct Answer: D. Both A and B.

Question 81: What is a mutation?

A. The process of passing traits from parents to offspring.
B. The generation of non-parental gene combinations.
C. The alteration of DNA sequences.
D. The division of cells.

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Correct Answer: C. The alteration of DNA sequences.

Question 82: What are chromosomal aberrations?

A. Abnormalities in the number of chromosomes.
B. Abnormalities in the structure of chromosomes.
C. Changes in a single base pair of DNA.
D. All of the above.

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Correct Answer: D. All of the above.

Question 83: What is a point mutation?

A. A change in the number of chromosomes.
B. A change in the structure of chromosomes.
C. A change in a single base pair of DNA.
D. A change in the environment.

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Correct Answer: C. A change in a single base pair of DNA.

Question 84: What is a mutagen?

A. An agent that induces mutations.
B. A gene that causes mutations.
C. A protein that repairs mutations.
D. An organism that is resistant to mutations.

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Correct Answer: A. An agent that induces mutations.

Question 85: What is an example of a mutagen?

A. UV radiation
B. X-rays
C. Certain chemicals
D. All of the above.

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Correct Answer: D. All of the above.

Question 86: What is the significance of mutations?

A. They can lead to genetic variation.
B. They can cause diseases.
C. They can be beneficial to an organism.
D. All of the above.

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Correct Answer: D. All of the above.

Question 87: What is the difference between a mutation and a chromosomal aberration?

A. A mutation is a change in a single base pair of DNA; a chromosomal aberration is a change in the number or structure of chromosomes.
B. A mutation is caused by the environment; a chromosomal aberration is inherited.
C. A mutation is always harmful; a chromosomal aberration can be beneficial.
D. There is no difference; they are the same thing.

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Correct Answer: A. A mutation is a change in a single base pair of DNA; a chromosomal aberration is a change in the number or structure of chromosomes.

Question 88: What is pedigree analysis?

A. Analyzing the inheritance patterns of traits in a family over generations.
B. Analyzing the DNA sequence of an individual.
C. Analyzing the chromosomes of an individual.
D. Analyzing the proteins of an individual.

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Correct Answer: A. Analyzing the inheritance patterns of traits in a family over generations.

Question 89: What are Mendelian disorders?

A. Disorders caused by environmental factors.
B. Disorders caused by multiple genes.
C. Disorders caused by alteration or mutation in a single gene.
D. Disorders that are not inherited.

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Correct Answer: C. Disorders caused by alteration or mutation in a single gene.

Question 90: What are examples of Mendelian disorders?

A. Haemophilia
B. Cystic fibrosis
C. Sickle-cell anaemia
D. All of the above.

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Correct Answer: D. All of the above.

Question 91: What are chromosomal disorders?

A. Disorders caused by alteration or mutation in a single gene.
B. Disorders caused by absence, excess, or abnormal arrangement of one or more chromosomes.
C. Disorders caused by environmental factors.
D. Disorders that are not inherited.

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Correct Answer: B. Disorders caused by absence, excess, or abnormal arrangement of one or more chromosomes.

Question 92: What are examples of chromosomal disorders?

A. Down’s syndrome
B. Turner’s syndrome
C. Klinefelter’s syndrome
D. All of the above.

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Correct Answer: D. All of the above.

Question 93: What is the difference between Mendelian disorders and chromosomal disorders?

A. Mendelian disorders are caused by mutations in a single gene; chromosomal disorders are caused by abnormalities in the number or structure of chromosomes.
B. Mendelian disorders are inherited in a predictable pattern; chromosomal disorders are not inherited.
C. Mendelian disorders are always recessive; chromosomal disorders are always dominant.
D. There is no difference; they are the same thing.

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Correct Answer: A. Mendelian disorders are caused by mutations in a single gene; chromosomal disorders are caused by abnormalities in the number or structure of chromosomes.

Question 94: What is haemophilia?

A. A genetic disorder that affects blood clotting.
B. A genetic disorder that affects the lungs.
C. A genetic disorder that affects the brain.
D. A genetic disorder that affects the skin.

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Correct Answer: A. A genetic disorder that affects blood clotting.

Question 95: What is cystic fibrosis?

A. A genetic disorder that affects blood clotting.
B. A genetic disorder that affects the lungs.
C. A genetic disorder that affects the brain.
D. A genetic disorder that affects the skin.

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Correct Answer: B. A genetic disorder that affects the lungs.

Question 96: What is sickle-cell anaemia?

A. A genetic disorder that affects blood clotting.
B. A genetic disorder that affects the lungs.
C. A genetic disorder that affects the shape of red blood cells.
D. A genetic disorder that affects the skin.

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Correct Answer: C. A genetic disorder that affects the shape of red blood cells.

Question 97: What is Down’s syndrome?

A. A chromosomal disorder caused by an extra copy of chromosome 21.
B. A chromosomal disorder caused by a missing X chromosome.
C. A chromosomal disorder caused by an extra X chromosome.
D. A chromosomal disorder caused by an extra Y chromosome.

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Correct Answer: A. A chromosomal disorder caused by an extra copy of chromosome 21.

Question 98: What is Turner’s syndrome?

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Correct Answer: B. A chromosomal disorder caused by a missing X chromosome.

Question 99: What is Klinefelter’s syndrome?

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Correct Answer: C. A chromosomal disorder caused by an extra X chromosome.

Question 100: What is the significance of genetic disorders?

A. They can help us understand the relationship between genes and traits.
B. They can provide insights into the development of new treatments.
C. They can raise ethical concerns about genetic testing and screening.
D. All of the above.

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Correct Answer: D. All of the above.