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Free Inheritance MCQs with Answers

1,238 Inheritance MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.

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Mendel's Laws of InheritanceGene Linkage and Crossing OverX-linked Recessive Inheritance
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1,238 questions · page 22 of 62

421. Which statement about dominant and recessive alleles is not correct?

  • A. A dominant characteristic is seen in the phenotype of a heterozygote.
  • B. A homozygous genotype may be either dominant or recessive.
  • C. Recessive phenotypes always have two recessive alleles.
  • D. The phenotype of a homozygote is always dominant.

Explanation: Phenotype of a homozygote can be dominant or recessive both AA or aa. Hence statement D is incorrect and our answer.

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Correct answer: The phenotype of a homozygote is always dominant.

422. Pick the correct option for Drosophila.

  • A. The Male is larger with a pointed abdomen
  • B. The female has sex combs on its front legs
  • C. It has a generation time of just eight weeks
  • D. Salivary gland cells have giant chromosomes in their nuclei

Explanation: Polytene chromosomes form in the Drosophila giant salivary gland during development by multiple rounds of genome replication without cell…

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Correct answer: Salivary gland cells have giant chromosomes in their nuclei

423. J. Seiler in 1914 discovered which type of sex determination in moths?

  • A. XO - XX
  • B. XY - XX
  • C. ZZ - ZW
  • D. None of the given options

Explanation: Even when two W chromosomes are paired to one Z chromosome in W 1W 2Z/ZZ systems, sex chromosome separation appears to be precise.

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Correct answer: ZZ - ZW

424. Discontinuous variations in a population were first observed by:

  • A. Mendel
  • B. Correns
  • C. Nilsson
  • D. Darwin

Explanation: Mendel's concept of the gene was based on the analysis of hereditary variants-organisms that show identifiable and persistent differences…

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Correct answer: Mendel

425. The genotype of blood group 'AB' in humans is _.

  • A. IA IB
  • B. IB Io
  • C. IA IA
  • D. IoIo

Explanation: ABO blood type in humans is determined by 3 alleles IA, IB (Dominant), and i (Recessive) Genotype IA shows blood group A.

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Correct answer: IA IB

426. An X to A ratio of ⅖ in drosophila produces:

  • A. Sterile female
  • B. Fertile female
  • C. Male
  • D. Both male and female but sterile

Explanation: An X to A ratio of 1.00 or higher produces females whereas an X : A ratio of 0.5 or less produces males.

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Correct answer: Male

427. Linked genes with closer loci _ Mendel's law of independent assortment as they _ assort independently.

  • A. Don't obey:cannot
  • B. Don't obey:can
  • C. obey:cannot
  • D. obey:can

Explanation: Mendel's law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of…

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Correct answer: Don't obey:cannot

428. Ahmed's blood could not clot properly; he was diagnosed with hemophilia A. He passed this trait to his grandson through his:

  • A. Wife
  • B. Son
  • C. Daughter
  • D. Brother

Explanation: X chromosome of the father is only transferred to the daughter, a son takes the Y chromosome and hemophilia is an X-linked disease Ahmed…

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Correct answer: Daughter

429. A continuously varying trait is encoded by alleles of two or more different genes located at different loci, all influencing the same trait in an additive way is known as _.

  • A. Polytraits
  • B. Polygenes
  • C. Multiple alleles
  • D. Different genes
  • E. Allele frequency

Explanation: Polygenic inheritance is a type of inheritance where a continuously varying trait is influenced by alleles of two or more different genes…

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Correct answer: Polygenes

430. The type of gene interaction in which the effect caused by a gene at one locus interferes with the effect caused by another gene at another locus is known as:

  • A. Pleiotropy
  • B. Epistasis
  • C. Polygenic inheritance
  • D. Gene linkage
  • E. Crossing over

Explanation: Option A: Pleiotropy is a gene interaction in which a single gene affects multiple traits.

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Correct answer: Epistasis

431. A pea plant has purple-colored flowers (dominant trait). To check the genotype, which of the following cross is performed

  • A. Test cross with homozygous white-flowered plant
  • B. Test cross with homozygous purple-flowered plant
  • C. Test cross with heterozygous purple-flowered plant
  • D. Hybird cross

Explanation: Option A: Test cross with homozygous white-flowered plant: This is the best option to determine the genotype of the plant with…

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Correct answer: Test cross with homozygous white-flowered plant

432. Two parents, one hemophilic and the other carrier female, chances among the male offspring to be hemophilic:

  • A. 25%
  • B. 50%
  • C. 75%
  • D. 100%

Explanation: In the extremely rare event that both the mother and father have the affected X chromosomes, there is a 50% chance that their sons will be…

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Correct answer: 50%

433. Which of the following blood transfusions can be made safely?

  • A. Group A to group B
  • B. Group B to group AB
  • C. Group AB to group O
  • D. Group A to group O

Explanation: Blood Group B can easily be transfused to the person having blood group AB, the reason being the person having blood group AB will have…

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Correct answer: Group B to group AB

434. Blood group AB is an example of _ .

  • A. Complete dominance
  • B. Recessive alleles
  • C. Co-dominance
  • D. Incomplete dominance

Explanation: Option A describes one allele being completely dominant over the other allele i.e.

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Correct answer: Co-dominance

435. Red-green color-blindness is an X-linked recessive disorder. Jacob's paternal grandfather and father are both color-blind, but his mother has two normal alleles. What is the probability that Jacob is red-green color-blind?

  • A. 0%
  • B. 25%
  • C. 50%
  • D. 75%

Explanation: In humans, red-green color-blindness is an X-linked recessive trait. Males (XY) will be color-blind if the gene is present on only their…

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Correct answer: 0%

436. The type of gene interaction in which the effect caused by a gene at one locus interfere with the effect caused by another gene at another locus is known as:

  • A. Pleiotropy
  • B. Epistasis
  • C. Polygenic inheritance
  • D. Gene linkage
  • E. Crossing over

Explanation: Option A refers to the phenomenon in which one gene has multiple phenotypic expressions.

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Correct answer: Epistasis

437. Read the passage below to answer the question: Haemophilia is a disorder in which blood fails to clot. Saad, a male haemophiliac, marries Sara, a normal woman and together they have four children, two boys (Ahmed and Ali) and two girls (Alia and Ayesha). None of the children displays the symptoms of Haemophilia. Ahmed, Ali, Ayesha, and Ali all marry normal individuals and have children. None of Ahmed's or Ali's children, male or female, display symptoms of haemophilia, but the sons of Alia and Ayesha display symptoms of haemophilia while the daughters of Alia and Ayesha do not. Which of the following best explains the reason that Ahmed, Ali, Ayesha and Alia do not display symptoms of haemophilia, even though their father, Saad, is a haemophiliac?

  • A. Haemophilia is an X-linked disorder, and Saad can only pass on his Y chromosome
  • B. Haemophilia is an X-linked disorder, and even though Alia and Ayesha received a hemophiliac X-chromosome from Saad, Sara gave them a normal X-chromosome
  • C. Haemophilia is a Y-linked disorder, and therefore cannot be displayed in females
  • D. Haemophilia is a Y-linked disorder ,and Ahmed and Ali must have received an X Chromosome from Saad
  • E. Haemophilia is an X-linked disorder, and even though Ahmed and All received a Hemophilia X chromosome from Saad, Sara gave them a normal X chromosome

Explanation: Haemophilia is an X-linked chromosome, not a Y-linked chromosome. Daughters of Sara and Saad, Alia and Ayesha receive an X chromosome from…

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Correct answer: Haemophilia is an X-linked disorder, and even though Alia and Ayesha received a hemophiliac X-chromosome from Saad, Sara gave them a normal X-chromosome

438. Read the passage below to answer the question: Hemophilia is a disorder in which blood fails to clot. Saad, a male hemophiliac, marries Sara, a normal woman and together they have four children, two boys (Ahmed and Ali) and two girls (Alia and Ayesha). None of the children display the symptoms of Hemophilia. Ahmed, Ali, Ayesha, and Ali all marry normal individuals and have children. None of Ahmed or Ali's children, male or female, display symptoms of hemophilia, but the sons of Alia and Ayesha display symptoms of hemophilia while the daughters of Alia and Ayesha do not. Which of the following individuals are heterozygous for hemophilia:

  • A. Saad, Ahmed, and Ali
  • B. Ahmed, Ali, Alia, and Ayesha
  • C. Saad and Sara
  • D. Alia and Ayesha
  • E. Ahmed and Ali

Explanation: Male can't be heterozygous or homozygous because they can only have one allele. Females can possibly be homozygous or heterozygous.

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Correct answer: Alia and Ayesha

439. Hybrid black Guinea pigs are crossed with each other. The resulting offspring will be:

  • A. All black
  • B. All white
  • C. 3 black, 1 white
  • D. 3 white, 1 black

Explanation: From the word hybrid we assume that the guinea pigs are heterozygous and because they are black so black is the dominant allele

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Correct answer: 3 black, 1 white

440. _ are more common in human males than females.

  • A. X-linked dominant traits
  • B. X-linked recessive traits
  • C. Y-linked dominant traits
  • D. Autosomal linked recessive traits

Explanation: Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much…

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Correct answer: X-linked recessive traits
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