48 past paper MCQs on Mendel's Laws of Inheritance, from the Inheritance unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.A test cross is made to check the genotype of a trait. Which of the following crosses is a test cross? (MDCAT 2022)
Correct answer: (b) unknown $\times$ tt
The homozygous recessive parent contributes no dominant allele, so the offspring reveal what the unknown carried.
2.A test cross is made to check the genotype of a trait. Which of the following crosses is a test cross? (MDCAT 2023)
Correct answer: (b) unknown $\times$ tt
Crossing with the homozygous recessive lets the unknown's alleles show in the offspring.
3.According to Mendel's law of segregation, one individual out of four in the $F_2$ generation had a phenotype that failed to express in which generation? (MDCAT 2023)
Correct answer: (a) $F_1$
The recessive phenotype is hidden in the $F_1$ and reappears in a quarter of the $F_2$.
4.Only those genes can assort independently whose loci are on: (MDCAT 2023)
Correct answer: (c) non-homologous chromosomes
Genes on different chromosomes are dealt out independently at meiosis; genes on one chromosome tend to travel together.
5.Self-fertilization in plants through successive generations can lead to the development of: (UHS MDCAT 2025)
Correct answer: (c) True breeding plants
Selfing raises homozygosity generation by generation until the line breeds true.
6.Mendel crossed a plant with round yellow seeds (RRYY) and a plant with wrinkled green seeds (rryy), what was the phenotype of all F1 offspring? (UHS MDCAT 2025)
Correct answer: (b) All round yellow
Round and yellow are dominant, so every RrYy offspring of the F1 shows both.
7.Which of Mendel's laws can best explain why a child may inherit brown eyes even if one parent has blue eyes? (KMU MDCAT 2025)
Correct answer: (a) Law of Dominance
The brown allele is dominant, so one copy is enough to show it.
8.What is the significance of the 9:3:3:1ratio in a dihybrid cross? (KMU MDCAT 2025)
Correct answer: (b) It demonstrates that traits assort independently
A 9:3:3:1 ratio is what two unlinked pairs of alleles give when each assorts independently.
9.If a round seeded pea plant is self-fertilized and all of its offspring are also round seeded: (SIBA MDCAT 2025)
Correct answer: (a) Both parents and offspring must be true breed
A plant that breeds true for a trait on selfing is homozygous for it, and so is its offspring.
10.The genetic makeup that your parents have transferred to you for your hair color, makes up your: (KMU MDCAT 2024)
Correct answer: (a) Genotype
The alleles inherited are the genotype; what shows is the phenotype.
11.Which term best describes an organism's physical characteristic. (KMU MDCAT 2024)
Correct answer: (d) Trait
A trait is a physical characteristic; the genotype is the alleles behind it.
12.What will be the probability of purple and terminal flower in Pea plant in F2 generation, if we cross true breeding purple axial with white terminal? (NUMS MDCAT 2024)
Correct answer: (b) 3/16
Purple and axial are dominant, so purple with terminal is $3/4\times1/4$, that is $3/16$.
13.Mode of inheritance in humans can be traced through: (UHS MDCAT 2023)
Correct answer: (c) Pedigree Analysis
Human families cannot be bred to order, so the record of a trait through the generations is what is read.
14.Mendelian inheritance follows which form of dominance relation? (SZABMU MDCAT 2023)
Correct answer: (a) Complete dominance
In each of Mendel’s pairs one allele masked the other completely.
15.When both the alleles of a gene pair are same, the organism is said to be: (NUMS MDCAT 2023)
Correct answer: (c) Homozygous
Two identical alleles make the organism homozygous for that gene.
16.According to Mendel Law of Segregation, the one individual out of four in F2 generation had phenotype that failed to express in generation. (UHS MDCAT 2023)
Correct answer: (a) F1
The recessive phenotype is hidden in the F1 and reappears in a quarter of the F2.
17.Test cross is made to check the genotype of a trait. Which of the following crosses is a test cross? (UHS MDCAT 2023)
Correct answer: (b) Unknown x tt
A test cross is with the homozygous recessive, whose gametes carry nothing to mask the unknown allele.
18.What is the ratio of homozygous dominant to homozygous recessive genotypes in F2 generation of monohybrid cross? (PMC MDCAT 2022)
Correct answer: (a) 1:1
The F2 is $1:2:1$, so the two homozygotes are in the ratio one to one.
19.Relatives who have children together have a much higher risk of having children affected by: (PMC MDCAT 2022)
Correct answer: (c) Recessive condition
Relatives share alleles, so a rare recessive is far more likely to meet its like.
20.If a heterozygous round pea plant is crossed with a wrinkled pea plant, what is the probability of homozygous phenotypes in the progeny? (PMC MDCAT 2022)
Correct answer: (b) 50%
A heterozygote crossed with the recessive gives half round and half wrinkled, and the wrinkled half is homozygous.
21.The traits that show autosomal inheritance have: (PMC MDCAT 2022)
Correct answer: (a) Equal probabilty in both male and female individuaIs
An autosome is inherited alike by both sexes, so the trait falls equally on sons and daughters.
22.Two phenotypically normal individuals have an affected child.What can we conclude about the parents? (PMC MDCAT 2022)
Correct answer: (a) Both parent carried the disease allele
The condition is recessive and neither parent shows it, so each must carry one copy.
23.When Mendel conducted his experiments, he needed to transfer pollen grains from a male reproductive organ to the female reproductive organ of the same plant. What is this process called: (PMC MDCAT 2022)
Correct answer: (b) Self polination
Pollinating a flower with its own pollen is self-pollination.
24.Homozygous dominants are represented with a : (PMC MDCAT 2022)
Correct answer: (c) Capital letter
A dominant allele is written as a capital letter, the recessive as the small one.
25.The alternative form of a given gene is called: (PMC MDCAT 2022)
Correct answer: (c) Allele
The alternative forms of a gene are its alleles.
26.Physical appearance of a trait is called: (PMC MDCAT 2022)
Correct answer: (c) Phenotype
What shows is the phenotype; what is carried is the genotype.
27.Albinism is an autosomal recessive trait. A woman with albino father marries an albino man. What Is the probability of albinism in her children? (PMC MDCAT 2022)
Correct answer: (b) 50%
Her father was albino, so she is a carrier; with an albino husband half the children are affected.
28.Phenotype represents: (PMC MDCAT 2022)
Correct answer: (a) Physical appereance of the trait
The phenotype is what shows; the genotype is what is carried.
29.Mendel’s idea that pair of characters separate during gamete formation is called: (PMC MDCAT 2022)
Correct answer: (b) Law of segregation
The law of segregation says the two alleles of a pair separate into different gametes.
30.A test cross is performed: (PMC MDCAT 2022)
Correct answer: (d) To determine whether an organism Is heterozygous or homozygous dominant
Crossing with the homozygous recessive shows at once whether the unknown carries a recessive allele.
31.What is the ratio of homozygous to heterozygous individuals in F2 generation of monohybrid cross? (PMC MDCAT 2022)
Correct answer: (a) 1 : 1
The F2 is $1:2:1$, so the two homozygotes together match the heterozygotes.
32.If both the alleles are same with respect to genes, then they are called? (PMC Practice 2021)
Correct answer: (c) Homozygous
Two identical alleles make the organism homozygous.
33.All of the following are continuously varying traits except? (PMC Practice 2021)
Correct answer: (d) Tongue rolling in humans
Tongue rolling is either present or absent; the other three vary continuously.
34.True breeding variety is produced by which of the following? (PMC Practice 2021)
Correct answer: (b) Self-fertilization
Selfing raises homozygosity generation by generation until the line breeds true.
35.In ‘Complete Dominance’: (PMC MDCAT 2020)
Correct answer: (b) One allele (R) is completely dominant over the other (r) and the presence of the recessive allele is functionally hidden, so the heterozygote (Rr) has the same round phenotype as (RR) homozygote.
Under complete dominance the heterozygote looks exactly like the dominant homozygote.
36.“Law of independent assortment” states: (PMC MDCAT 2020)
Correct answer: (a) That each pair of alleles assort independently of other pairs of alleles during gamete formation
Each pair of alleles goes into the gametes independently of every other pair.
37.______ alleles both have an effect on the phenotype of a heterozygous organism: (PMC MDCAT 2020)
Correct answer: (c) Co-dominant
Codominant alleles are both expressed in the heterozygote.
38.Phenotype is: (PMC MDCAT 2020)
Correct answer: (c) The form of appearance of a trait
The phenotype is what shows; the genotype is what is carried.
39.Homozygous means: (UHS MDCAT 2019)
Correct answer: (d) having two identical alleles of a gene.
Homozygous means the two alleles of the gene are alike.
40.A person was married to his cousin and both are heterozygous for Sickle Cell anemia. Among their four kids, what will be proportion of homozygotes? (UHS MDCAT 2019)
Correct answer: (b) 50%
The cross gives $1:2:1$, so half the children are homozygous, one way or the other.
41.Blood group AB is an example of __________ . (UHS MDCAT 2019)
Correct answer: (c) Co-dominance
Both alleles are expressed, so both antigens appear on the cells.
42.When two or more alleles do not show complete dominance or both the alleles are expressing independently in heterozygotic condition. Such a condition is called: (UHS MDCAT 2018)
Correct answer: (c) Codominance
Codominant alleles are both expressed in the heterozygote.
43.Which one of the following is Multiple allelic characters? (UHS MDCAT 2018)
Correct answer: (b) Blood group of the human being
The ABO system has three alleles, so it is an example of multiple alleles.
44.The phenotype of heterozygote is distinct from those of the two homozygotes, not an intermediate expression, this is termed as: (UHS MDCAT 2017)
Correct answer: (d) Codominance
Codominance shows both alleles in the heterozygote rather than a blend.
45.When an effect caused by a gene or gene pair at one locus interferes with or or hides the effect caused by another gene or gene pair at another locus, the phenomena is called (UHS MDCAT 2017)
Correct answer: (c) Epistasis
One gene masking the effect of another at a different locus is epistasis.
46.A character determined by three alleles is: (UHS MDCAT 2016)
Correct answer: (b) Human blood group
The ABO system has three alleles, of which each person carries two.
47.Human skin colour is a good example of? (UHS MDCAT 2015)
Correct answer: (b) Polygenic inheritance
Skin colour is set by several genes together, which is polygenic inheritance.
48.ABO blood system is an example of: (UHS MDCAT 2015)
Correct answer: (c) Multiple Alleles
The ABO system has three alleles, of which each person carries two.