Test: Genetics - 1 - Class 10 MCQ

Genetics is the branch of science which deals with the study of:
- Heredity: Genetics focuses on the study of how traits are passed down from one generation to another. It explores the principles of inheritance and the transmission of genetic information through genes.
- Variation: Genetics also examines the variations that occur within a species, including the factors that contribute to genetic diversity. It explores the mechanisms of genetic mutations and how they can lead to variations in traits.
- Genes and Chromosomes: Genetics delves into the structure and function of genes, which are segments of DNA that contain the instructions for building and maintaining an organism. It also studies chromosomes, which are structures within cells that carry genes.
- Genetic Disorders: Genetics investigates the causes and mechanisms of genetic disorders, such as inherited diseases and conditions that can be passed down from parents to their offspring. It aims to understand the underlying genetic factors and develop strategies for diagnosis, treatment, and prevention.
- Genetic Engineering: Genetics explores the field of genetic engineering, which involves manipulating and modifying the genetic material of organisms. It investigates techniques such as gene editing, gene therapy, and genetic modification, with the aim of improving human health, agriculture, and other areas.
- Evolution: Genetics plays a crucial role in the study of evolution, as it helps explain how populations change over time and how new species arise. It provides insights into the mechanisms of natural selection, genetic drift, and other factors that drive evolutionary processes.
Overall, genetics is a broad field that encompasses the study of heredity, variation, genes, chromosomes, genetic disorders, genetic engineering, and evolution. It provides valuable insights into the fundamental principles of life and has significant implications for various fields, including medicine, agriculture, and conservation.

Explanation:
The term 'genetics' was coined by William Bateson. Here is a detailed explanation:
1. Introduction:
- The term 'genetics' refers to the branch of biology that deals with the study of genes, heredity, and variation in living organisms.
- The term was first used in the early 20th century to describe the study of inheritance and the mechanisms by which traits are passed from parents to offspring.
2. William Bateson:
- William Bateson, an English biologist, is credited with coining the term 'genetics.'
- He introduced the term in his book "Mendel's Principles of Heredity" published in 1905.
- Bateson was one of the early pioneers in the field of genetics and played a crucial role in popularizing the work of Gregor Mendel, an Austrian monk who is considered the father of modern genetics.
3. Gregor Mendel:
- Although Gregor Mendel is known for his groundbreaking work on pea plants and the discovery of fundamental laws of inheritance, he did not coin the term 'genetics.'
- Mendel's work laid the foundation for the field of genetics, but it was William Bateson who gave it a distinct name.
4. Other Contributions:
- While Thomas Hunt Morgan and W. Johannsen made significant contributions to the field of genetics, they did not coin the term 'genetics.'
- Thomas Hunt Morgan is known for his research on fruit flies and the discovery of sex-linked inheritance, while W. Johannsen introduced the concept of genes as discrete units of heredity.
Conclusion:
- In conclusion, the term 'genetics' was coined by William Bateson, an English biologist, in the early 20th century.
- Bateson's work and the introduction of this term helped establish genetics as a distinct field of study within biology.

Introduction:
The term 'gene' is a fundamental concept in genetics, and it refers to a specific sequence of DNA or RNA that is responsible for the inheritance of a particular trait. In this question, we are asked to identify the person who introduced the term 'gene.'
Answer:
The correct answer is D. Johannsen.
Explanation:
Wilhelm Johannsen, a Danish botanist, introduced the term 'gene' in the early 20th century. He used this term to describe the units of hereditary information that determine the characteristics of an organism. Johannsen's work focused on studying the inheritance of traits in plants, particularly in relation to their observable variations.
Additional Information:
While Johannsen coined the term 'gene,' it is important to note that the concept of inheritance and the study of genetics had been developing for many years before him. Key contributors to the field of genetics include:
- Gregor Mendel (A): Mendel, an Austrian monk, is often referred to as the father of genetics. In the mid-19th century, he conducted groundbreaking experiments on pea plants and formulated the laws of inheritance that laid the foundation for modern genetics.
- William Bateson (B): Bateson, an English biologist, was a prominent early advocate of Mendel's work. He played a crucial role in popularizing Mendel's laws of inheritance and promoting the study of genetics in the early 20th century.
- Thomas Hunt Morgan (C): Morgan, an American geneticist, made significant contributions to the field of genetics, particularly in understanding the role of chromosomes in inheritance. His work with fruit flies led to the discovery of sex-linked traits and the concept of gene linkage.
In conclusion, while Johannsen is credited with introducing the term 'gene,' it is important to recognize the contributions of other scientists in the development of genetics as a field of study.

When a gene exists in more than one form, the different forms are termed:
The correct answer is alleles.
Explanation:
- Alleles are alternative forms of a gene that occupy the same position on a chromosome.
- They can be different versions of a gene that result in different traits or characteristics.
- Alleles can be dominant or recessive, with dominant alleles being expressed in the phenotype when present and recessive alleles only being expressed when two copies are present.
- Alleles can also be co-dominant, where both alleles are expressed in the phenotype.
- The presence of multiple alleles for a gene in a population contributes to genetic variation.
- The term "heterozygotes" refers to individuals who have two different alleles for a particular gene.
- "Genotypes" refer to the genetic makeup of an individual, which includes the combination of alleles they possess.
- "Complementary genes" refer to a pair of genes that interact to produce a specific phenotype.
In summary, when a gene exists in more than one form, these different forms are called alleles.

The contrasting pairs of factors on Mendelian crosses are called allelomorphs. Alleles or allelomorphs are the different forms of a gene, having the same locus on homologous chromosome. 

An allele is a variant form of a given gene, meaning it is one of two or more versions of a known mutation at the same place on a chromosome.

Homologs/ homologous chromosomes have the same genes i.e. alleles in the same loci where they provide points along each chromosome which enable a pair of chromosomes to align correctly with each other before separating during meiosis.

An allele is a variant form of a given gene. On a chromosome, genes are encoded through different nucleotide sequences in DNA, and thus have a specific spot on the chromosome. The spot where a gene is located is called the locus. Genes may possess multiple variants known as alleles, and an allele may also be said to reside at a particular locus.

Organism receiving identical alleles of a particular gene from both parents is a homozygote.
Explanation:
- Homozygote: An organism that receives identical alleles for a particular gene from both parents is called a homozygote.
- Homozygotes can be either homozygous dominant (having two dominant alleles) or homozygous recessive (having two recessive alleles).
- In a homozygote, both alleles are the same, resulting in the expression of the same trait or characteristic.
- The alleles received from each parent can be either dominant or recessive, but they are always identical.
- Homozygotes are often used in genetic studies to understand the inheritance patterns of specific traits.
- The opposite of a homozygote is a heterozygote, where an organism receives different alleles for a particular gene from each parent.
- Homozygotes can be advantageous in some cases, such as when the identical alleles provide resistance to a particular disease or increase fitness in a specific environment.

Genetic Complement of an Organism
The genetic complement of an organism refers to the complete set of genes or genetic material that an organism possesses. It determines the characteristics and traits of an individual.
Options:
A. Genotype
- The correct answer is A. Genotype. The term "genotype" specifically refers to the genetic makeup or genetic constitution of an organism. It encompasses all the genes, including dominant and recessive alleles, that an individual carries.
B. Physiotype
- Physiotype is not the correct answer. The term "physiotype" is not commonly used in genetics. It may be confused with the term "phenotype," which refers to the observable physical and biochemical characteristics of an organism.
C. Phenotype
- Phenotype is not the correct answer. While phenotype is an important concept in genetics, it does not represent the genetic complement of an organism. Phenotype refers to the physical manifestation of an organism's genotype, including its observable traits and characteristics.
D. Morphotype
- Morphotype is not the correct answer. The term "morphotype" is not commonly used in genetics. It may be confused with the term "phenotype," which represents the physical characteristics of an organism.
In conclusion, the correct answer is A. Genotype, as it accurately represents the genetic complement of an organism.

Phenotype:
- The physical appearance of an individual is known as the phenotype.
- It refers to the observable characteristics or traits of an organism.
- These traits can include physical features such as height, eye color, hair type, and skin color.
- Phenotype is determined by a combination of genetic factors (genotype) and environmental influences.
- It is the result of the expression of genes, which can be influenced by various factors such as nutrition, lifestyle, and exposure to certain substances.
- The phenotype can vary among individuals, even if they have the same genotype, due to differences in gene expression and environmental factors.
- Studying the phenotype is important in fields such as genetics, medicine, and anthropology to understand the relationship between genes, traits, and diseases.
- The phenotype can be observed and measured through various methods, including physical examination, imaging techniques, and genetic testing.

Introduction:
The terms 'genotype' and 'phenotype' are commonly used in the field of genetics to describe different aspects of an organism's genetic makeup and observable characteristics. These terms were introduced by different scientists who made significant contributions to the understanding of genetics.
Johannsen and the term 'phenotype':
- Wilhelm Johannsen, a Danish botanist, introduced the term 'phenotype' in 1911.
- Johannsen used this term to describe the observable characteristics of an organism, such as its physical appearance, behavior, and other traits.
- He emphasized that the phenotype is the result of the interaction between the genotype (the genetic information) and the environment.
Mendel and the term 'genotype':
- Gregor Mendel, an Austrian monk and scientist, conducted groundbreaking experiments with pea plants in the mid-19th century.
- Although Mendel did not use the term 'genotype' explicitly, his experiments laid the foundation for understanding the concept.
- Mendel's work focused on the inheritance of traits and the idea that these traits are determined by discrete units of inheritance, which he called 'factors'. These factors are now known as genes.
- The genotype refers to the specific combination of genes an organism possesses.
Bateson and the popularization of the terms:
- William Bateson, an English biologist, played a crucial role in popularizing the terms 'genotype' and 'phenotype'.
- Bateson was a strong supporter of Mendel's principles of inheritance and worked to promote Mendel's ideas in the scientific community.
- He used the terms 'genotype' and 'phenotype' in his writings to describe the underlying genetic information and the observable traits, respectively.
Conclusion:
- The terms 'genotype' and 'phenotype' were introduced by different scientists who made significant contributions to the field of genetics.
- Wilhelm Johannsen introduced the term 'phenotype' to describe the observable characteristics of an organism.
- Gregor Mendel's experiments laid the foundation for understanding the concept of 'genotype', referring to the specific combination of genes an organism possesses.
- William Bateson played a crucial role in popularizing these terms and promoting Mendel's principles of inheritance.

Mendel's Most Important Contribution to the Modern Understanding of Biology:

• The concept that hereditary information comes in discrete units:




• Mendel's experiments with pea plants led him to propose that hereditary traits are determined by discrete units of information.


• He called these units "factors" or "genes."


• This concept laid the foundation for the understanding of inheritance and the study of genetics.






• The concept of meiosis:




• Mendel's work indirectly contributed to the understanding of meiosis.


• Meiosis is the process by which cells divide to produce gametes (sex cells) with half the number of chromosomes.


• Mendel's observations of inheritance patterns in pea plants hinted at the existence of a mechanism that ensures the separation and recombination of genetic material during gamete formation.






• The concept of chromosome:




• Mendel's experiments did not directly involve the concept of chromosomes.


• However, his work laid the groundwork for understanding the relationship between genes and chromosomes.


• Later discoveries confirmed that genes are located on chromosomes, which are thread-like structures that carry genetic information.






• The concept that genes are ordered along chromosomes:




• Mendel's experiments did not directly address the concept of gene order along chromosomes.


• However, his work paved the way for understanding the principles of genetic linkage and mapping.


• Subsequent studies revealed that genes are arranged in a linear fashion along chromosomes.

Therefore, Mendel's most significant contribution to the modern understanding of biology is his concept that hereditary information comes in discrete units, which are now known as genes.

Gregor Mendel was a scientist, Augustinian friar and Abbot of St. Thomas ' Abbey in Brno, of Moravia. Mendel was born in a German speaking family in the part of Austrian Empire. 

Mendelism is related with:
- Heredity in living beings: Mendelism is primarily concerned with the study of heredity, which is the passing of traits from parents to offspring. It explores the patterns and principles of inheritance in living organisms.
- Meiosis during sexual reproduction: Mendelism is closely associated with the process of meiosis, which occurs during sexual reproduction. Meiosis is the cell division that produces gametes (sex cells) with half the number of chromosomes as the parent cell. Mendel's experiments with pea plants involved the study of traits passed down through the process of sexual reproduction.
- Mutations in living organisms: While Mendelism primarily focuses on the principles of inheritance, it does not directly deal with mutations. Mutations are changes in the DNA sequence that can lead to variations in traits. However, Mendel's work laid the foundation for the understanding of genetic mutations and their inheritance patterns in subsequent studies.
- None of the above: This option is incorrect as Mendelism is indeed related to heredity and the process of meiosis during sexual reproduction.
In conclusion, Mendelism is primarily concerned with the study of heredity and the principles of inheritance in living organisms, particularly through the process of sexual reproduction. While it does not directly deal with mutations, it laid the groundwork for understanding genetic variations and their inheritance patterns.

Answer:
Mendel published the results of his experiments in the year:
- Mendel published the results of his experiments in the year 1866.
- This is denoted by option C in the given choices.
- Mendel's experiments were focused on studying the inheritance of traits in pea plants.
- He conducted his experiments between 1856 and 1863.
- After analyzing his results, Mendel published his findings in 1866 under the title "Experiments on Plant Hybridization".
- In his publication, Mendel described the principles of inheritance and introduced the concept of dominant and recessive traits.
- However, Mendel's work was initially overlooked and it was not until the early 20th century that his experiments gained recognition and became the foundation of modern genetics.
- Mendel's publication in 1866 laid the groundwork for the understanding of genetic inheritance and the development of the field of genetics.

The three biologists who independently rediscovered Mendel's principles in 1900 AD were Hugo de Vries, Carl Correns, and Erich Tschermak. Let's break down the answer into headings and bullet points for a clear and organized explanation:
Rediscovery of Mendel's Principles:
- In 1865, Gregor Mendel, an Austrian monk, published his groundbreaking work on the principles of inheritance, now known as Mendelian genetics.
- However, Mendel's work went largely unnoticed until the turn of the 20th century when three biologists independently rediscovered his principles.
The Three Biologists:
1. Hugo de Vries:
- Hugo de Vries was a Dutch botanist who rediscovered Mendel's laws of inheritance in 1900.
- He was studying the inheritance patterns of evening primroses (Oenothera lamarckiana) when he noticed the occurrence of distinct traits in the offspring, which aligned with Mendel's principles.
- De Vries coined the term "mutation" and proposed the theory of mutationism, which suggested that new species arise from sudden, large-scale changes in genetic material.
2. Carl Correns:
- Carl Correns was a German botanist who also independently rediscovered Mendel's principles in 1900.
- Correns was working with the plant species Four o'clock (Mirabilis jalapa) and observed patterns of inheritance that were consistent with Mendel's laws.
- He conducted experiments to verify the laws of segregation and independent assortment proposed by Mendel.
3. Erich Tschermak:
- Erich Tschermak, an Austrian botanist, was the third biologist to rediscover Mendel's principles in 1900.
- Tschermak was conducting experiments with peas similar to Mendel's original work when he independently arrived at Mendel's laws of inheritance.
- He published his findings, acknowledging the prior work of Mendel.
Conclusion:
In summary, the three biologists who independently rediscovered Mendel's principles in 1900 AD were Hugo de Vries, Carl Correns, and Erich Tschermak. Their rediscovery played a crucial role in establishing the field of modern genetics and solidifying the importance of Mendel's work.

Contrasting Traits Studied by Mendel:
Mendel's experiments with pea plants involved the study of several contrasting traits. He meticulously observed and recorded the characteristics of the plants and their offspring. The traits studied by Mendel can be summarized as follows:
1. Seed Color:
- Contrasting traits: Yellow seeds vs. Green seeds.
2. Seed Shape:
- Contrasting traits: Round seeds vs. Wrinkled seeds.
3. Flower Color:
- Contrasting traits: Purple flowers vs. White flowers.
4. Flower Position:
- Contrasting traits: Axial flowers (along the stem) vs. Terminal flowers (at the tip of the stem).
5. Pod Color:
- Contrasting traits: Green pods vs. Yellow pods.
6. Pod Shape:
- Contrasting traits: Inflated pods vs. Constricted pods.
7. Stem Length:
- Contrasting traits: Tall stems vs. Dwarf stems.
Therefore, Mendel studied a total of seven contrasting traits in pea plants. These traits played a crucial role in his formulation of the laws of inheritance and laid the foundation for modern genetics.

Answer:
Mendel studied various traits of garden pea plants and conducted experiments to understand their inheritance patterns. Out of the traits he studied, the recessive feature was the green seed color. Here is a detailed explanation of each trait and why green seed color is the recessive feature:
1. Green seed color:
- Pea plants typically have yellow seed color, but some plants have green seeds.
- When Mendel crossed true-breeding yellow seed plants with true-breeding green seed plants, all the offspring had yellow seeds.
- In the next generation (F2), when he crossed the yellow-seeded plants from the previous generation, he observed a 3:1 ratio of yellow to green seeds, indicating that the green seed color is a recessive trait.
2. Green pod color:
- Mendel also studied the pod color of pea plants.
- However, the pod color trait he studied was yellow (dominant) versus green (recessive).
- Green pod color was not a trait specifically studied by Mendel.
3. Round seed shape:
- Mendel also investigated the shape of the pea seeds.
- He found that round seed shape was dominant over wrinkled seed shape.
- Therefore, round seed shape was not a recessive trait.
4. Axial flower position:
- Mendel examined the position of flowers on the plant.
- He observed that flowers could be either axial (located along the stem) or terminal (located at the end of the stem).
- Axial flower position was found to be dominant over terminal flower position.
- Thus, axial flower position was not a recessive trait.
In conclusion, out of the traits studied by Mendel, the recessive feature was the green seed color.

Contributions to the success of Mendel:
1. His knowledge of biology:
- Mendel's background in biology allowed him to understand the basic principles of inheritance and genetics.
- He was knowledgeable about the reproductive processes of plants, which allowed him to perform experiments and make accurate observations.
2. Qualitative analysis of data:
- Mendel meticulously collected and analyzed data from his experiments.
- He focused on qualitative traits, such as flower color or seed texture, rather than just counting the number of offspring.
- This approach allowed him to identify distinct patterns of inheritance and formulate his laws of genetics.
3. Observation of distinct inherited traits:
- Mendel chose to study traits that were easily distinguishable and occurred in distinct forms, such as tall vs. short plants or yellow vs. green peas.
- By selecting traits with clear-cut variations, he was able to easily track their inheritance patterns and make accurate predictions.
4. Consideration of one character at a time:
- Instead of studying multiple traits simultaneously, Mendel focused on one trait, such as flower color, in each experiment.
- This allowed him to establish clear and consistent patterns of inheritance for each trait and avoid confusion or overlap between different traits.
In conclusion, Mendel's success can be attributed to his knowledge of biology, his qualitative analysis of data, his observation of distinct inherited traits, and his consideration of one character at a time. These factors enabled him to make significant discoveries in the field of genetics and lay the foundation for modern understanding of inheritance.

Reasons why pea plants were more suitable than dogs for Mendel's experiments:
1. Pea plants can be self-fertilized:
- Pea plants have both male and female reproductive organs, allowing them to self-fertilize.
- This characteristic allowed Mendel to control the breeding process and ensure the traits he wanted to study were passed on to the next generation.
2. Dogs have many genetic traits:
- Dogs exhibit a wide range of genetic traits, making it difficult to isolate and study specific traits.
- Mendel needed a plant species with easily distinguishable and contrasting traits to observe the patterns of inheritance, which pea plants provided.
3. There are no pedigree records of dogs:
- Pedigree records, which document the lineage and genetic information of individuals, were not available for dogs during Mendel's time.
- Pea plants, on the other hand, were easier to track and study due to their simple genetic makeup and the ability to control their breeding.
4. The pea plants favor cross-fertilization:
- Pea plants naturally undergo cross-fertilization, where pollen from one plant is transferred to the female reproductive organ of another plant.
- This allowed Mendel to intentionally cross-pollinate plants with different traits, leading to the observation of predictable patterns of inheritance.
In conclusion, Mendel chose pea plants for his experiments because they could be easily self-fertilized, had distinct and observable traits, had available pedigree records, and naturally favored cross-fertilization. These characteristics made pea plants a more suitable choice for his groundbreaking studies on inheritance.

Reasons why Mendel chose pea plants:
1. Contrasting characters: Pea plants have distinct and easily observable traits that exhibit clear-cut variations. Mendel specifically selected pea plants with well-defined and contrasting characteristics, such as tall vs. short height, yellow vs. green seed color, and smooth vs. wrinkled seed texture. This allowed him to easily analyze and track the inheritance patterns of these traits.
2. Ease of cultivation: Pea plants are relatively easy to grow and maintain, making them suitable for conducting experiments. They have a short life cycle, allowing Mendel to observe multiple generations in a relatively short period of time. Additionally, pea plants are self-fertilizing, which means they can reproduce through self-pollination, ensuring the purity of the traits being studied.
3. Abundance and availability: Pea plants are widely available and can be easily obtained from various sources. This accessibility allowed Mendel to conduct his experiments on a large scale and obtain sufficient data for statistical analysis.
4. Structural features: Pea plants have certain structural features that facilitated Mendel's experiments. For example, their flowers have both male and female reproductive organs, making it possible to cross-pollinate different plants and control the breeding process. The prominent position of the reproductive organs also made it easier for Mendel to perform controlled crosses.
5. Generalizability: Mendel believed that the principles of inheritance he discovered in pea plants could be applied to other organisms as well. By studying a widely recognized and commonly studied plant, Mendel aimed to establish a foundation for understanding the inheritance patterns and laws that govern all living organisms.
In conclusion, Mendel chose pea plants for their contrasting characters, ease of cultivation, abundance and availability, structural features, and the potential to generalize his findings to other organisms. These factors made pea plants an ideal choice for his groundbreaking experiments in genetics.

Selection of homozygous plant is:
There are several methods used for the selection of homozygous plants, but the most common and effective method is pure line selection.
- Pure line selection: This method involves selecting and breeding plants that exhibit homozygosity for the desired traits. The process includes the following steps:
- Identify plants with desirable traits: Select plants that exhibit the desired characteristics such as disease resistance, high yield, or specific agronomic traits.
- Self-pollination: Allow the selected plants to self-pollinate, ensuring that the offspring inherit the same set of genes.
- Observe uniformity: Observe the progeny of the self-pollinated plants and select those that show uniformity in the desired traits.
- Repeated cycles: Repeat the process of self-pollination and selection for several generations to achieve a stable homozygous line.
- Mass selection: Although mass selection is a commonly used breeding method, it does not specifically target the production of homozygous plants. Mass selection involves selecting and breeding plants based on overall performance without considering homozygosity.
- Mixed selection: Mixed selection is not a method used for the selection of homozygous plants. It refers to a breeding method where different breeding techniques, such as mass selection and hybridization, are combined.
- None of the above: This option is incorrect as pure line selection is the most suitable method for selecting homozygous plants.
In conclusion, the correct answer is pure line selection when it comes to selecting homozygous plants. This method ensures the production of plants with stable and uniform traits through multiple generations of self-pollination and selection.

When a cross is made between two parents with respect to a single character, it is called Monohybrid Cross.
Explanation:
A monohybrid cross is a genetic cross between two individuals that differ in a single trait or character. In this type of cross, only one trait is considered and its inheritance is studied. The parents involved in the cross are called the P generation (parental generation).
Here is a detailed explanation of the monohybrid cross:
1. P Generation: The two parents with contrasting traits are selected for the cross. For example, let's consider the trait of flower color in pea plants - one parent has white flowers (recessive trait) and the other parent has purple flowers (dominant trait).
2. Gamete Formation: Each parent produces gametes, which are the reproductive cells (eggs and sperm). The white-flowered parent will produce gametes with the allele for white flowers (recessive allele), while the purple-flowered parent will produce gametes with the allele for purple flowers (dominant allele).
3. F1 Generation: The gametes from the two parents combine to form the first filial (F1) generation. The resulting offspring will all have the same genotype, with one allele from each parent. In the example, all the F1 generation plants will have the genotype Pp (one dominant allele and one recessive allele).
4. Phenotypic Ratio: The phenotypic ratio of the F1 generation will depend on the dominance and recessiveness of the traits. In this case, since purple flowers are dominant over white flowers, all the F1 plants will have purple flowers.
5. F2 Generation: To study the inheritance pattern, a cross is made between two F1 plants. The resulting offspring are called the second filial (F2) generation. In the F2 generation, the genotype and phenotype ratios can be determined.
6. Genotypic and Phenotypic Ratios: In the F2 generation, the genotypic ratio will be 1:2:1 (1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive). The phenotypic ratio will be 3:1 (3 plants with purple flowers and 1 plant with white flowers).
In conclusion, when a cross is made between two parents with respect to a single character, it is called a monohybrid cross. This type of cross helps in understanding the inheritance pattern of a specific trait.

Monohybrid Ratio:
The monohybrid ratio refers to the ratio of phenotypes that result from a cross between two individuals heterozygous for a single gene. It is used to predict the outcome of a single trait inheritance.
Options:
A: 3 : 1
B: 9 : 7
C: 1 : 2
D: 9 : 3

To determine the correct monohybrid ratio, we need to consider the genotypes of the parents and the possible combinations of alleles that can be inherited by their offspring.
- The monohybrid ratio is determined by the inheritance pattern of a single gene.
- In this case, we are not given any specific information about the parents or the gene being considered.
- However, based on the options provided, we can eliminate options B, C, and D as they do not represent a typical monohybrid ratio.
Explanation:
A monohybrid cross involves the inheritance of a single gene from each parent. The possible combinations of alleles that can be inherited are:
- Homozygous dominant (AA)
- Heterozygous (Aa)
- Homozygous recessive (aa)
Based on these combinations, the expected phenotypic ratio for a monohybrid cross is:
- 3 individuals with the dominant phenotype (AA or Aa)
- 1 individual with the recessive phenotype (aa)
Therefore, the correct monohybrid ratio is option A: 3 : 1.

The reason is simple, it was due to the Monohybrid cross that Mendel could find that characters that we are not expressed in the To generation where expressed in F2 generation. This could mean gametes independently contains alleles.