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Genetics: Principles of Inheritance and Variation MCQ Test

Test your comprehensive knowledge of genetics, including Mendelian inheritance, deviations, chromosomal theory, and genetic disorders, drawing from key biological principles.

Test Your Knowledge

Showing questions 1 - 20 of 44

1. What is the branch of biology that scientifically deals with the inheritance and variation of characters from parents to offspring?

Ecology
Physiology
Genetics
Biotechnology

The subject of Genetics deals with the inheritance, as well as the variation of characters from parents to offspring.

2. Who first applied statistical analysis and mathematical logic to problems in biology while investigating inheritance patterns?

James Watson
Francis Crick
Gregor Mendel
Thomas Hunt Morgan

During Mendel’s investigations into inheritance patterns, it was for the first time that statistical analysis and mathematical logic were applied to problems in biology.

3. A true-breeding line, as used by Mendel in his experiments, is characterized by:

Producing offspring with varied traits in each generation.
Showing stable trait inheritance and expression for several generations after continuous self-pollination.
Being the result of cross-pollination between two different varieties.
Always exhibiting the recessive trait.

A true-breeding line is one that, having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations.

4. In Mendel's monohybrid cross between true-breeding tall and dwarf pea plants, what was observed in the first hybrid generation (F1 progeny)?

All plants were dwarf.
All plants were tall.
Plants showed an intermediate height.
Both tall and dwarf plants appeared in a 1:1 ratio.

Mendel observed that all the F1 progeny plants were tall, like one of its parents; none were dwarf.

5. What was the phenotypic ratio observed in the F2 generation of a Mendelian monohybrid cross?

1:2:1
3:1
9:3:3:1
1:1

In the F2 generation, 3/4th of the plants were tall while 1/4th were dwarf, leading to a phenotypic ratio of 3:1.

6. Which of the following statements accurately describes 'factors' as proposed by Mendel?

They are unstable units that blend during inheritance.
They are currently known as genes and are units of inheritance.
They always express themselves whether homozygous or heterozygous.
They are only found in dominant forms.

Mendel proposed that something was being stably passed down, unchanged, from parent to offspring through the gametes, over successive generations. He called these things as 'factors'. Now we call them as genes. Genes, therefore, are the units of inheritance.

7. If 'TT' represents the genotype for a tall pea plant, and 'tall' is its phenotype, what would be the phenotype of a plant with genotype 'Tt' according to Mendel's observations on pea height?

Dwarf
Intermediate height
Tall
Cannot be determined

As Mendel found the phenotype of the F1 heterozygote Tt to be exactly like the TT parent in appearance, he proposed that in a pair of dissimilar factors, one dominates the other (as in the F1) and hence is called the dominant factor.

8. The Law of Segregation is based on which of the following facts regarding alleles during gamete formation?

Alleles blend completely.
Both alleles are transmitted to every gamete.
Alleles segregate from each other, and each gamete receives only one allele.
Alleles are always expressed, regardless of their pairing.

This law is based on the fact that the alleles do not show any blending and that both the characters are recovered as such in the F2 generation though one of these is not seen at the F1 stage. Though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors.

9. What is the primary purpose of a test cross?

To determine the genotypic ratio of the F2 generation.
To confirm the dominance of a trait.
To determine the genotype of an organism showing a dominant phenotype.
To obtain a true-breeding line.

To determine the genotype of a tall plant at F2, Mendel crossed the tall plant from F2 with a dwarf plant. This he called a test cross. In a typical test cross an organism showing a dominant phenotype (and whose genotype is to be determined) is crossed with the recessive parent instead of self-crossing.

10. In snapdragon (Antirrhinum sp.) flowers, a cross between true-breeding red (RR) and white (rr) flowered plants produces F1 progeny with pink flowers. This phenomenon is an example of:

Co-dominance
Complete Dominance
Incomplete Dominance
Pleiotropy

When experiments on peas were repeated using other traits in other plants, it was found that sometimes the F1 had a phenotype that did not resemble either of the two parents and was in between the two. The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance.

11. ABO blood grouping in humans is a classic example of:

Incomplete dominance
Multiple alleles
Co-dominance
Both B and C

ABO blood groups are controlled by the gene I, which has three alleles IA, IB and i. The alleles IA and IB are completely dominant over i, but when IA and IB are present together they both express their own types of sugars, which is co-dominance. Since there are more than two alleles, it also provides a good example of multiple alleles.

12. According to the sources, a recessive trait is seen because the modified allele typically produces:

A more efficient enzyme.
A non-functional enzyme or no enzyme.
The same phenotype as the unmodified allele.
An enzyme that enhances the substrate transformation.

The unmodified (functioning) allele, which represents the original phenotype is the dominant allele and the modified allele is generally the recessive allele. Hence, in the example above the recessive trait is seen due to non-functional enzyme or because no enzyme is produced.

13. Which of the following human diseases is given as an example of pleiotropy, where a single gene mutation results in multiple phenotypic expressions like mental retardation and reduced hair/skin pigmentation?

Sickle-cell anaemia
Haemophilia
Thalassemia
Phenylketonuria

An example of pleiotropy is the disease phenylketonuria, which occurs in humans. The disease is caused by mutation in the gene that codes for the enzyme phenyl alanine hydroxylase. This manifests itself through phenotypic expression characterised by mental retardation and a reduction in hair and skin pigmentation.

14. In Mendel's dihybrid cross, the phenotypic ratio observed in the F2 generation was:

1:2:1
3:1
9:3:3:1
1:1:1:1

In the dihybrid cross, the phenotypes round, yellow; wrinkled, yellow; round, green and wrinkled, green appeared in the ratio 9:3:3:1.

15. Mendel's Law of Independent Assortment states that:

Factors blend in the F1 generation.
When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters.
Dominant traits always mask recessive traits.
Each gamete receives two alleles for each gene.

The law states that 'when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters'.

16. Which of the following was NOT a reason for Mendel's work remaining unrecognised until 1900?

Lack of easy communication at the time.
His concept of discrete units not accepted due to continuous variation.
His use of mathematics in biology was novel and unacceptable.
He failed to provide any experimental evidence for his laws.

Mendel's work was unrecognised until 1900 due to poor communication, his concept of genes as stable and discrete units was not accepted due to apparent continuous variation, and his mathematical approach was new and unacceptable to biologists. While he could not provide physical proof for 'factors', his inferences were confirmed by experiments on successive generations, indicating strong experimental evidence for his results.

17. The Chromosomal Theory of Inheritance was proposed by:

James Watson and Francis Crick
Gregor Mendel
Walter Sutton and Theodore Boveri
Thomas Hunt Morgan

Walter Sutton and Theodore Boveri noted that the behaviour of chromosomes was parallel to the behaviour of genes and used chromosome movement to explain Mendel’s laws. Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it the chromosomal theory of inheritance.

18. Which of the following is NOT an advantage of using Drosophila melanogaster (fruit flies) for genetic studies?

They have a long life cycle, allowing for observation of many generations.
They can be grown on simple synthetic medium in the laboratory.
A single mating produces a large number of progeny flies.
There is a clear differentiation of sexes.

Drosophila melanogaster is suitable because they complete their life cycle in about two weeks (a short life cycle), not a long one. They also can be grown on simple medium, produce large progeny, and have clear sex differentiation.

19. The term 'linkage' describes the physical association of genes on a chromosome, while 'recombination' describes:

The blending of parental traits.
The independent assortment of all genes.
The generation of non-parental gene combinations.
The process of gamete formation.

Morgan coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of non-parental gene combinations.

20. Who used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and 'mapped' their position on the chromosome?

T.H. Morgan
Alfred Sturtevant
Gregor Mendel
Walter Sutton

Morgan's student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and 'mapped' their position on the chromosome.

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Reproductive Health: MCQ Test

Molecular Basis of Inheritance: MCQ Test

biology

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