101. What percentage of the F2 generation is expected to show the dominant phenotype in a standard monohybrid cross?
ⓐ. 75%
ⓑ. 50%
ⓒ. 25%
ⓓ. 100%
Correct Answer: 75%
Explanation: The F2 phenotypic ratio in a simple monohybrid cross is $3:1$. This means three out of four individuals show the dominant phenotype. Converting $\frac{3}{4}$ into percentage gives 75%. The recessive phenotype occupies the remaining 25%.
102. In the F2 generation of a monohybrid cross for plant height, what fraction of the plants are expected to be pure tall?
ⓐ. $\frac{1}{2}$
ⓑ. $\frac{3}{4}$
ⓒ. $\frac{1}{4}$
ⓓ. $\frac{2}{4}$
Correct Answer: $\frac{1}{4}$
Explanation: The F2 genotypic ratio is $1TT:2Tt:1tt$. The pure tall plants are the homozygous dominant individuals, represented by $TT$. Since only one out of four plants has this genotype, the expected fraction is $\frac{1}{4}$. This is different from the fraction of all tall plants, which is $\frac{3}{4}$.
103. Which statement best expresses the law of dominance?
ⓐ. Two different gene pairs always assort independently during gamete formation.
ⓑ. In a pair of contrasting factors, one can express itself in the heterozygote and mask the other.
ⓒ. Recessive traits are always absent from the offspring of a cross.
ⓓ. Every character is controlled by blending of parental factors.
Correct Answer: In a pair of contrasting factors, one can express itself in the heterozygote and mask the other.
Explanation: The law of dominance describes what happens when two contrasting alleles come together in a heterozygous condition. One allele expresses itself in the phenotype, while the other remains unexpressed. This explains why only one parental trait may appear in the F1 generation. The law is about expression, not about permanent loss of the recessive factor.
104. Which statement about a dominant trait is incorrect?
ⓐ. It must always be more common in a population than the recessive trait.
ⓑ. It is expressed in the heterozygous condition.
ⓒ. It can mask the expression of a recessive allele in F1.
ⓓ. It may appear in both homozygous and heterozygous individuals.
Correct Answer: It must always be more common in a population than the recessive trait.
Explanation: Dominance refers to expression in a heterozygote, not to how common a trait is in a population. A dominant trait may be rare, and a recessive trait may be common. The terms dominant and recessive describe allele interaction, not population frequency. Confusing these ideas is a common mistake in genetics.
105. A heterozygous plant for height has the genotype $Tt$. According to the law of dominance, why does it appear tall?
ⓐ. Both alleles blend to form a tall phenotype.
ⓑ. The recessive allele changes into a dominant allele.
ⓒ. The plant contains two tall alleles.
ⓓ. The dominant allele expresses itself and masks the recessive allele.
Correct Answer: The dominant allele expresses itself and masks the recessive allele.
Explanation: In the genotype $Tt$, the two alleles are different, yet only the dominant trait appears. This happens because the dominant allele determines the phenotype in the heterozygous state. The recessive allele remains present but is not expressed. The result is a tall plant that still carries the dwarf allele.
106. In a monohybrid cross, which observation is the strongest evidence against blending inheritance?
ⓐ. The parental plants show contrasting forms of a character.
ⓑ. The F1 generation is uniform for one trait.
ⓒ. The recessive trait reappears unchanged in the F2 generation.
ⓓ. The dominant phenotype is more frequent than the recessive phenotype.
Correct Answer: The recessive trait reappears unchanged in the F2 generation.
Explanation: Blending inheritance would predict that once traits mix, the original forms should not return in unchanged form. Mendel observed that the recessive trait disappeared in F1 but reappeared in F2. This showed that hereditary factors remain distinct rather than blending permanently. The result strongly supported particulate inheritance.
107. Among the tall plants in the F2 generation of a monohybrid cross, the ratio of homozygous tall to heterozygous tall is
ⓐ. $3:1$
ⓑ. $1:2$
ⓒ. $2:1$
ⓓ. $1:1$
Correct Answer: $1:2$
Explanation: In F2, the genotypic ratio is $1TT:2Tt:1tt$. If only the tall plants are considered, the relevant genotypes are $TT$ and $Tt$. Their ratio becomes $1:2$. This shows that not all tall plants in F2 are genetically identical.
108. A tall pea plant from the F2 generation is self-pollinated for several generations and always produces only tall offspring. What is the most likely genotype of the original F2 plant?
ⓐ. $TT$
ⓑ. $Tt$
ⓒ. $tt$
ⓓ. It cannot be either homozygous or heterozygous
Correct Answer: $TT$
Explanation: A plant that continues to produce only tall offspring on repeated selfing is behaving as a true-breeding tall line. That is expected when the genotype is homozygous dominant, $TT$. A heterozygous tall plant would eventually produce some dwarf offspring on selfing. Stable uniform tall progeny therefore point to the $TT$ genotype.
109. Which statement is the best illustration of the law of dominance?
ⓐ. In a heterozygous condition, one factor expresses itself while the other remains masked.
ⓑ. The two alleles of a gene always move together into the same gamete.
ⓒ. Every dominant trait is more common in nature than the recessive trait.
ⓓ. Contrasting parental traits permanently blend in the offspring.
Correct Answer: In a heterozygous condition, one factor expresses itself while the other remains masked.
Explanation: The law of dominance explains what happens when two contrasting factors are present together in one individual. In such a case, one factor is expressed in the phenotype, while the other does not appear externally. This is why the F1 generation of a simple monohybrid cross shows only one parental trait. The masked factor is still present and can reappear later.
110. Which statement about dominance is incorrect?
ⓐ. A dominant allele may be present in both homozygous and heterozygous conditions.
ⓑ. A dominant trait can appear in the F1 generation of a monohybrid cross.
ⓒ. Dominance refers to expression in a heterozygous condition.
ⓓ. A dominant trait is always superior or more useful than a recessive trait.
Correct Answer: A dominant trait is always superior or more useful than a recessive trait.
Explanation: Dominance does not mean better, stronger, or more useful. It only means that one allele expresses itself in the presence of another allele in a heterozygous individual. A recessive trait is not inferior simply because it is masked in that condition. The term describes expression, not biological value.
111. In the genotype $Tt$, the allele $T$ is called dominant because it
ⓐ. occurs in larger numbers in the species
ⓑ. expresses itself in the presence of $t$
ⓒ. can never be separated from $t$
ⓓ. always produces true-breeding offspring
Correct Answer: expresses itself in the presence of $t$
Explanation: A dominant allele is identified by its ability to appear in the phenotype even when paired with an alternative allele. In the heterozygous genotype $Tt$, the trait controlled by $T$ is visible, while the effect of $t$ is masked. This definition depends on expression pattern, not on frequency in the population. Dominance is therefore a functional term in inheritance.
112. Which statement best expresses the law of segregation?
ⓐ. One allele always becomes stronger than the other during fertilisation.
ⓑ. Two different gene pairs always assort independently of each other.
ⓒ. The two alleles of a gene separate during gamete formation, so each gamete receives only one allele.
ⓓ. Dominant and recessive alleles combine permanently in the offspring.
Correct Answer: The two alleles of a gene separate during gamete formation, so each gamete receives only one allele.
Explanation: The law of segregation states that the two alleles present in a diploid organism do not remain together in the same gamete. They separate when gametes are formed, and each gamete receives only one allele of the pair. This idea is sometimes called the purity of gametes. It explains how hidden alleles can pass unchanged to the next generation.
113. Which phrase is most closely associated with the law of segregation?
ⓐ. Purity of gametes
ⓑ. Blending of characters
ⓒ. Superiority of dominant traits
ⓓ. Continuous variation
Correct Answer: Purity of gametes
Explanation: The law of segregation is closely linked with the idea that gametes are pure for a character. A diploid organism carries two alleles, but only one of them enters a given gamete. Because of this separation, alleles do not blend or lose their identity. The concept helps explain the reappearance of recessive traits in later generations.
114. A pea plant with genotype $Tt$ forms gametes. Which statement is correct?
ⓐ. Every gamete carries both $T$ and $t$.
ⓑ. Half the gametes carry $TT$, and half carry $tt$.
ⓒ. All gametes carry only $T$ because it is dominant.
ⓓ. Some gametes carry $T$, and others carry $t$.
Correct Answer: Some gametes carry $T$, and others carry $t$.
Explanation: A heterozygous plant contains two different alleles for the same gene, but they separate during gamete formation. As a result, one type of gamete carries $T$ and the other carries $t$. A gamete is haploid, so it cannot carry both alleles of the pair together. This is a direct consequence of segregation.
115. If the law of segregation did not operate, what would be expected during gamete formation in a diploid organism?
ⓐ. All gametes would be identical in every trait.
ⓑ. Both alleles of a gene pair would enter the same gamete together.
ⓒ. Dominant alleles would vanish after one generation.
ⓓ. Recessive alleles would be unable to enter gametes.
Correct Answer: Both alleles of a gene pair would enter the same gamete together.
Explanation: Segregation ensures that the two alleles of a gene pair separate and move into different gametes. If that did not happen, gametes would carry both alleles together, which is not the normal pattern in Mendelian inheritance. The transmission of hereditary factors would then be fundamentally different. The law is important because it preserves one-allele-per-gamete inheritance.
116. Which statement correctly distinguishes the law of dominance from the law of segregation?
ⓐ. Dominance explains separation of alleles, while segregation explains expression in F1.
ⓑ. Dominance applies only to animals, while segregation applies only to plants.
ⓒ. Dominance explains expression of one allele in a heterozygote, while segregation explains separation of alleles during gamete formation.
ⓓ. Dominance and segregation are two names for the same genetic principle.
Correct Answer: Dominance explains expression of one allele in a heterozygote, while segregation explains separation of alleles during gamete formation.
Explanation: These two laws describe different parts of inheritance. Dominance deals with which allele is seen in the phenotype when unlike alleles are present together. Segregation deals with how those alleles separate when gametes are formed. Keeping the two ideas distinct is essential for understanding monohybrid inheritance correctly.
117. Which observation from Mendel’s experiments is best explained by the law of segregation?
ⓐ. A recessive trait that disappears in F1 reappears in F2.
ⓑ. All F1 plants show the dominant phenotype.
ⓒ. Dominant traits are always more common than recessive traits.
ⓓ. A heterozygote produces only one type of gamete.
Correct Answer: A recessive trait that disappears in F1 reappears in F2.
Explanation: The return of the recessive trait in F2 shows that its factor was not destroyed in the F1 generation. It remained present and was transmitted through gametes because the alleles separated during gamete formation. When two recessive alleles came together again in F2, the recessive phenotype reappeared. This is one of the clearest outcomes supporting segregation.
118. Which set correctly represents the kinds of gametes produced by the three genotypes $TT$, $Tt$, and $tt$?
ⓐ. $TT \rightarrow T,T$ ; $Tt \rightarrow TT,tt$ ; $tt \rightarrow t,t$
ⓑ. $TT \rightarrow TT$ ; $Tt \rightarrow Tt$ ; $tt \rightarrow tt$
ⓒ. $TT \rightarrow T,t$ ; $Tt \rightarrow T,t$ ; $tt \rightarrow T,t$
ⓓ. $TT \rightarrow T$ only ; $Tt \rightarrow T$ and $t$ ; $tt \rightarrow t$ only
Correct Answer: $TT \rightarrow T$ only ; $Tt \rightarrow T$ and $t$ ; $tt \rightarrow t$ only
Explanation: A homozygous dominant individual can contribute only the dominant allele to its gametes, and a homozygous recessive individual can contribute only the recessive allele. A heterozygous individual produces two types of gametes because its unlike alleles separate during gamete formation. This pattern follows directly from the law of segregation. It also forms the basis of Punnett square analysis in monohybrid crosses.
119. Which statement directly follows from the law of segregation for a heterozygous individual $Tt$?
ⓐ. It produces two kinds of gametes, $T$ and $t$.
ⓑ. It produces only one kind of gamete because $T$ is dominant.
ⓒ. It produces gametes carrying both $T$ and $t$ together.
ⓓ. It produces only recessive gametes in the next generation.
Correct Answer: It produces two kinds of gametes, $T$ and $t$.
Explanation: A heterozygous individual carries two unlike alleles for the same gene. During gamete formation, these alleles separate from each other. As a result, one set of gametes receives $T$, while the other receives $t$. This is the basic meaning of segregation in a monohybrid situation.
120. In Mendelian genetics, the phrase “purity of gametes” means that
ⓐ. every gamete contains both alleles of a gene pair
ⓑ. each gamete carries only one allele of a gene pair
ⓒ. gametes always carry only dominant alleles
ⓓ. recessive alleles cannot enter gametes
Correct Answer: each gamete carries only one allele of a gene pair
Explanation: The idea of purity of gametes comes from the separation of alleles during gamete formation. A diploid organism has two alleles for a gene, but a gamete receives only one of them. This keeps the hereditary units distinct instead of mixed. The concept is central to the law of segregation.
