RBSE Solutions Class 10 Science Chapter 3 Genetics

I. Multiple Choice Questions

Question 1. Who coined the term 'genetics'?
(a) Mendel
(b) Bateson
(c) Morgan
(d) Punette
Answer: (b) Bateson
In simple words: Bateson was the scientist who first used the word 'genetics'. This new word helped to describe how traits are passed down through generations.

🎯 Exam Tip: Remember key scientists and their contributions to the field of genetics, especially the origin of fundamental terms.

Question 2. Mendel conducted his experiments on which of the following?
(a) Sweet pea
(b) Wild pea
(c) Garden pea
(d) All of the options
Answer: (c) Garden pea
In simple words: Mendel did his science tests using garden pea plants. These plants were good for studying how different features are passed on because they are easy to grow and have clear traits.

🎯 Exam Tip: It's crucial to know the specific organism Mendel chose, as its characteristics were ideal for his experiments.

Question 3. What is the name of the branch of science which deals with heredity and variations?
(a) Heredity
(b) Geology
(c) Forestry
(d) None of the options
Answer: (a) Heredity
In simple words: The science that studies how features are passed from parents to children, and why there are differences, is called genetics. Heredity is about passing traits, and variations are the differences we see.

🎯 Exam Tip: Clearly distinguish between heredity (the process of passing traits) and genetics (the scientific study of heredity and variation).

Question 4. The green colour of pea pod is which type of character?
(a) Dominant
Answer: (a) Dominant
In simple words: In pea plants, the green color of the pod is a strong trait. This means it will show up even if another trait for pod color is present.

🎯 Exam Tip: Understand the difference between dominant and recessive traits, as it's a core concept in Mendelian genetics.

Question 5. A gene generally has how many alleles?
(a) Four
(b) Three
(c) Two
(d) One
Answer: (c) Two
In simple words: Usually, a gene has two different forms, which are called alleles. These two forms decide what trait will show up in an individual.

🎯 Exam Tip: Remember that while a gene can have multiple alleles in a population, an individual typically inherits two alleles for each gene (one from each parent).

Question 6. Mendel selected how many inheritable pairs of traits for his experiments?
(a) 34
(b) 2
(c) 12
(d) 7
Answer: (d) 7
In simple words: Mendel chose seven different pairs of features to study in his pea plants. These features were clear and easy to track over generations.

🎯 Exam Tip: Knowing the exact number of traits Mendel studied helps demonstrate a thorough understanding of his experimental design.

Question 7. Which term is used for cross of any one parent with F₁ generation?
(a) Reciprocal cross
(b) Test cross
(c) Back cross
(d) All of the options
Answer: (c) Back cross
In simple words: When you cross a plant from the first generation (F₁) with any of its original parents, it is called a back cross. This helps scientists understand the genetics better.

🎯 Exam Tip: Differentiate between a test cross (F1 with recessive parent) and a back cross (F1 with either parent), as both are used in genetic analysis.

Question 8. What will be the ratio of progenies after crossing Tt x tt?
(a) 3: 1
(b) 1:1
(c) 1:2:1
(d) 2:1
Answer: (b) 1:1
In simple words: If you cross a plant with one dominant and one recessive trait (Tt) with a plant that has two recessive traits (tt), the children plants will have an equal chance of being tall (Tt) or short (tt). This gives a 1:1 ratio.

🎯 Exam Tip: Practice drawing Punnett squares for various crosses to quickly determine genotypic and phenotypic ratios.

Question 9. What character did Mendel choose for his experiments?
(a) Colour of roots
(b) Colour of flowers
(c) Colour of seeds
(d) Colour of pods
Answer: (a) Colour of roots
In simple words: Mendel picked root color as one of the features to study in his pea plants. He looked at how this specific trait was passed on through generations.

🎯 Exam Tip: Be familiar with the specific traits Mendel studied in pea plants to answer such questions accurately.

Question 10. How many genotypes are formed in F2 generation after monohybrid cross?
(a) 2
(b) 3
(c) 4
(d) 9
Answer: (b) 3
In simple words: After a simple cross focusing on one trait (monohybrid cross), the second generation (F2) will show three different combinations of genes. These are the genetic makeups like TT, Tt, and tt.

🎯 Exam Tip: For a monohybrid cross, the F2 generation typically has 3 genotypes (e.g., TT, Tt, tt) and 2 phenotypes (e.g., Tall, Short).

Genetics Very Short Answer Type Questions

Question 11. Who is called as father of genetics?
Answer: Gregor Mendel is known as the father of genetics. He was a monk who did important experiments with pea plants and discovered the basic rules of heredity.
In simple words: Gregor Mendel is known as the father of genetics. He was a monk who did important experiments with pea plants.

🎯 Exam Tip: Always remember Gregor Mendel's name when discussing the basic principles of heredity.

Question 12. Mendel conducted his experiments on which plants?
Answer: Mendel carried out all his famous experiments on pea plants. These plants were chosen because they had clear traits and grew quickly, making them ideal for genetic studies.
In simple words: Mendel carried out all his famous experiments on pea plants. These plants were chosen because they had clear traits and grew quickly.

🎯 Exam Tip: It's vital to know that Mendel's choice of pea plants was a key factor in the success of his experiments.

Question 13. What is a dominant trait?
Answer: A dominant trait is a character that shows up or expresses itself in the first generation (F₁). Even if only one copy of the gene for this trait is present, it will still appear. For instance, in pea plants, tallness is a dominant trait over short stature.
In simple words: A dominant trait is a strong feature that always shows up in a living thing, even if there's only one instruction for it. It covers up other weaker features.

🎯 Exam Tip: Explain that dominant traits are observed phenotypically even in heterozygous conditions.

Question 14. What is inheritance?
Answer: Inheritance is the process where features and characteristics are passed down from parents to their children. This is how family traits continue through generations, ensuring genetic continuity.
In simple words: Inheritance is how children get features like eye color or height from their parents. It is the way traits are passed down.

🎯 Exam Tip: Use simple terms to explain that inheritance is the transmission of genetic information from one generation to the next.

Question 15. Who rediscovered the Mendel's laws?
Answer: Hugo de Vries, Carl Correns, and Erick von Tschermak were the three scientists who independently rediscovered Mendel's laws many years after his initial publication. Their work confirmed the importance of Mendel's findings.
In simple words: Three scientists named Hugo de Vries, Carl Correns, and Erick von Tschermak found Mendel's laws again many years later. They worked separately but came to the same findings.

🎯 Exam Tip: Note the three scientists independently rediscovered Mendel's work, which highlights the scientific validity and reproducibility of his findings.

Question 16. What is the full name of Mendel?
Answer: Mendel's complete name was Gregor John Mendel. He is globally recognized for his pivotal work in genetics.
In simple words: Mendel's complete name was Gregor John Mendel. He was very important for understanding how traits are passed on.

🎯 Exam Tip: Make sure to include both first and last names when asked for the full name of a prominent scientist.

Question 17. Write the names of laws proposed by Mendel.
Answer: Following laws were proposed by Mendel:
• Law of dominance
• Law of segregation
• Law of independent assortment
These three laws form the cornerstone of Mendelian genetics.
In simple words: Mendel gave three main rules about how traits are passed down. These are the Law of Dominance, the Law of Segregation, and the Law of Independent Assortment. Each rule helps us understand different parts of heredity.

🎯 Exam Tip: List all three of Mendel's laws clearly and concisely.

Question 18. What is test cross?
Answer: When an F₁ generation organism is crossed with a parent that has recessive traits, this specific type of cross is called a test cross. This helps to find out the unknown genotype of the F₁ organism, especially if it shows a dominant phenotype.
In simple words: A test cross is when you breed the first generation offspring (F₁) with a parent that only shows weaker traits. It helps to check what genes the F₁ has.

🎯 Exam Tip: Emphasize that a test cross specifically uses a recessive parent to determine the genotype of an unknown dominant phenotype.

Question 19. What do you understand by out cross?
Answer: When the F₁ generation is crossed with its parent's generation that shows dominant traits, this is known as an out cross. This type of cross helps to introduce new desirable traits into a population by increasing genetic variation.
In simple words: An out cross happens when you breed the first generation offspring (F₁) with a parent that shows strong, dominant traits. It helps to mix new genes into a family line.

🎯 Exam Tip: Distinguish an out cross from a back cross by noting that an out cross specifically involves a dominant parent from the parental generation.

Genetics Short Answer Type Questions

Question 21. What is the difference between phenotype and genotype?
Answer: The set of all observable physical characteristics of an organism, like its height or flower color, is called its phenotype. On the other hand, the genotype refers to the specific genetic makeup of an organism, which determines these traits. Two plants might look the same (same phenotype) but have different genes (different genotype). For example, a tall plant could be TT or Tt. Understanding this difference is key to studying heredity.
In simple words: Phenotype is how a living thing looks on the outside, like its color or size. Genotype is the hidden genetic code inside that makes it look that way.

🎯 Exam Tip: Clearly define both terms and provide a simple example to illustrate the distinction.

Question 22. Briefly explain dihybrid cross.
Answer: A dihybrid cross is a genetic experiment where two different pairs of contrasting traits are studied at the same time. For instance, if a pea plant is studied for both its flower color (e.g., purple or white) and its pod color (e.g., green or yellow), this would be considered a dihybrid cross. It helps to understand how different traits are inherited together and independently.
In simple words: A dihybrid cross looks at two different features at the same time, like the color of flowers and the color of pods. This helps us see how these two features are passed down together.

🎯 Exam Tip: Highlight that a dihybrid cross involves tracking the inheritance patterns of two distinct traits simultaneously.

Question 23. What were the reasons for success of Mendel?
Answer: Following are the reasons for Mendel's success:
• Mendel studied only one set of character at a time, making his observations clear and easy to analyze.
• He carefully performed statistical analysis of his findings, which gave his work a strong scientific basis and accuracy.
• He chose the garden pea plant specifically for his study because it had many desirable characteristics for genetic experiments.
These systematic approaches helped him uncover the laws of inheritance.
In simple words: Mendel was successful for a few reasons. He looked at one feature at a time, he used math to check his results, and he chose the perfect plant (pea plant) for his tests.

🎯 Exam Tip: List and briefly explain at least three key reasons for Mendel's success, focusing on his methodological approach and choice of organism.

Question 24. Why did Mendel select pea plant for his experiments?
Answer: Mendel chose pea plants for his experiments due to the following reasons:
• Pea plants are annual, meaning they complete their life cycle in one year, allowing many generations to be studied quickly.
• They produce bisexual flowers, which enables self-pollination to obtain pure lines (homozygous plants) easily. Self-pollination simplifies breeding experiments.
• Pea plant can be easily subjected to cross pollination by emasculation, a process of removing male parts to control which plants breed.
• Pea plant shows many pairs of contrasting characters which are inheritable, such as tall/short or green/yellow seeds, making observations straightforward.
These characteristics made the pea plant an ideal model organism for his genetic studies.
In simple words: Mendel picked pea plants because they grow fast, have both male and female parts in their flowers, can be easily cross-bred, and have many clear features that are passed down.

🎯 Exam Tip: Focus on the biological advantages of pea plants for genetic studies: short life cycle, ease of controlled breeding, and distinct observable traits.

Question 26. Explain the Law of Dominance as proposed by Mendel.
Answer: The Law of Dominance states that when two different contrasting characters are crossed, only one of these characters will appear in the first generation (F₁) offspring. This character, which is expressed, is called the dominant trait. The other character remains hidden, but is not lost. For example, if a pure tall pea plant (TT) is crossed with a pure short pea plant (tt), all the plants in the F₁ generation will be tall (Tt). This happens because tallness is the dominant character, overshadowing shortness.
In simple words: Mendel's Law of Dominance means that if you cross two different traits, only the strong one (dominant) will show up in the first set of children. The weaker trait hides but is still there.

🎯 Exam Tip: Clearly define dominance and provide an illustrative example, such as the tall vs. short pea plant cross in F1 generation.

Question 27. Write the significance of Mendel's Laws of Inheritance.
Answer: The significance of Mendel's Laws of Inheritance includes:
• The presence of a dominant trait often ensures that harmful traits, which are usually recessive, are suppressed and do not appear in every generation.
• The Law of Independent Assortment confirms the idea that genes are distinct units that separate and combine freely, supporting the gene concept and how traits can assort independently.
• These laws help explain how new combinations of traits can appear, leading to variations within a species and providing raw material for evolution.
• By understanding these principles, scientists can carefully select and breed plants to create new varieties with desired characteristics, improving crops and livestock.
In simple words: Mendel's laws are important because they show how bad traits can be hidden, how genes work independently, how new features can appear, and how we can breed better plants or animals.

🎯 Exam Tip: Focus on the practical and theoretical implications of Mendel's laws, such as genetic counseling, selective breeding, and understanding variation.

Genetics Long Answer Type Questions

Question 29. What is Mendelism? Explain the law of independent assortment.
Answer: Mendelism refers to the entire body of principles and laws of inheritance derived from Gregor Mendel's groundbreaking work. These laws collectively form the foundation of classical genetics and explain how traits are passed from parents to offspring.
**Law of Independent Assortment:** This law states that when organisms with two or more different contrasting characters are crossed, the expression of one character does not influence the expression or inheritance of another character. In simpler terms, alleles for different traits (located on different chromosomes or far apart on the same chromosome) segregate independently of each other during the formation of gametes (sex cells). They are free to combine with any other gene from any other pair of alleles. This random assortment creates genetic diversity.
**Example:** Let us consider a dihybrid cross between a plant with round and green seeds (RRyy) and another plant with wrinkled and yellow seeds (rrYY). Here roundness (R) and yellow color (Y) are dominant traits, while wrinkles (r) and green color (y) are recessive traits. When these plants are crossed, all plants in the F₁ generation produce round and yellow seeds (RrYy).
When the F₁ generation plants are allowed to self-pollinate, the F2 generation shows various traits in specific ratios. The diagram summarizes these results:

This phenotypic ratio of 9:3:3:1 demonstrates that the trait for roundness can combine with either yellow or green color, and wrinkledness can also combine with either yellow or green color. This independent combining of traits proves the law of independent assortment.
In simple words: Mendelism is all about Mendel's rules for how features are passed down. The Law of Independent Assortment means that when parents pass on different features, like seed shape and seed color, these features are passed on separately. One feature doesn't affect how the other feature is given. So, a round seed can be green or yellow; it does not have to be yellow always.

🎯 Exam Tip: Define Mendelism clearly. For the Law of Independent Assortment, focus on the "independent segregation" of different gene pairs and use the dihybrid cross example to illustrate the 9:3:3:1 ratio.

Question 30. Explain Mendel's Laws of Inheritance.
Answer: Gregor Mendel proposed several fundamental laws that govern heredity, collectively known as Mendel's Laws of Inheritance:
**Law of Dominance:** This law states that when a pair of contrasting characteristics (alleles) is present, only one of them, the dominant trait, will be expressed in the first filial (F₁) generation. The recessive trait remains hidden. For example, if a homozygous tall plant (TT) is crossed with a homozygous short plant (tt), all the F₁ generation plants are tall (Tt) because tallness is the dominant character.
**Law of Segregation:** This law describes how the two alleles for each trait separate, or segregate, during the formation of gametes (sex cells). Each gamete receives only one allele from the pair. This ensures that a recessive character, even if hidden in the F₁ generation, can reappear in the F2 generation. This separation is a crucial step in sexual reproduction.
**Example for Law of Segregation:** When F₁ generation tall plants (Tt) are self-pollinated, the gametes T and t separate. In the F2 generation, the plants show a phenotypic ratio of 3 tall : 1 short. This demonstrates that the alleles for tallness and shortness segregated during gamete formation and then recombined randomly.

The F2 generation has a phenotypic ratio of 3 Tall : 1 Short, and a genotypic ratio of 1 TT : 2 Tt : 1 tt.
**Law of Independent Assortment:** This law states that alleles for different traits are inherited independently of each other. In other words, the inheritance of one trait does not affect the inheritance of another. This leads to new combinations of traits in the offspring. This independence explains why traits like seed color and seed shape can be inherited separately.
In simple words: Mendel made rules for how features are passed down. The Law of Dominance says that one feature can be stronger and hide another. The Law of Segregation says that the two copies of each gene separate when new life cells are made. The Law of Independent Assortment means that different features, like seed shape and color, are passed down separately and don't affect each other.

🎯 Exam Tip: For explaining Mendel's laws, define each law clearly and provide a concise example for Law of Dominance and Law of Segregation. Refer to the dihybrid cross for Independent Assortment.

Genetics Additional Questions Solved

I. Multiple Choice Questions

Question 1. Which of the following is a totally impossible outcome of Mendel's Experiment (cross breeding pure bred tall and short pea plants)?
(a) 3 tall 1 short plant
(b) 24 tall and 8 short plants
(c) 8 tall and 0 short plants
(d) 4 tall plants and 1 medium-height plant
Answer: (d) 4 tall plants and 1 medium-height plant
In simple words: Mendel's experiments with pure tall and short pea plants never resulted in medium-height plants. This outcome would be impossible based on his findings, which showed clear dominant and recessive traits without intermediate forms.

🎯 Exam Tip: Mendel's experiments showed complete dominance, meaning intermediate traits like "medium-height" were not observed for the characters he studied. This is a key principle of Mendelian inheritance.

Question 2. Among the following which is not one of the direct conclusions that can be drawn from Mendel's experiment?
(a) Only one parental trait is expressed in F₁ generation.
(b) Two copies of each trait is inherited in sexually reproducing organism
(c) For recessive trait to be expressed, both copies should be identical.
(d) Natural selection can alter frequency of an inherited trait.
Answer: (d) Natural selection can alter frequency of an inherited trait.
In simple words: Mendel's work showed how traits are passed down and expressed, but it did not directly talk about how natural selection changes how often certain traits appear in a group of living things over time. This concept was developed by Darwin.

🎯 Exam Tip: Mendel's laws describe the mechanics of inheritance, while natural selection (a concept from Darwin) describes how trait frequencies change in populations due to environmental pressures.

Question 4. Which of the following shows homozygous genotype?
(a) TT
(b) Tt
(c) Rr
(d) Yy
Answer: (a) TT
In simple words: A homozygous genotype means that an organism has two identical copies of a gene for a specific trait. Among the given options, 'TT' shows two identical capital 'T' alleles.

🎯 Exam Tip: Remember that homozygous genotypes have two identical alleles (e.g., TT or tt), while heterozygous genotypes have two different alleles (e.g., Tt).

Question 5. Which trait will contrast with green colour?
(a) Tall plant
(b) Yellow colour
(c) Round seed
(d) Wrinkled seed
Answer: (b) Yellow colour
In simple words: In pea plants, the color that is opposite to green is yellow. So, yellow color is the contrasting trait for green color when discussing seed or pod colors.

🎯 Exam Tip: For contrasting traits in Mendel's experiments, remember the pairs he studied, such as yellow vs. green seeds or tall vs. dwarf plants.

Question 6. How many pairs of contrasting traits are studied in trihybrid cross?
(a) One
(b) Two
(c) Three
(d) Six
Answer: (c) Three
In simple words: A trihybrid cross is a genetic study where three different pairs of opposite traits are observed at the same time. This means you are looking at three characteristics, like height, seed color, and seed shape.

🎯 Exam Tip: The prefix "tri-" in trihybrid cross indicates that three distinct pairs of contrasting traits are being studied.

Question 8. After monohybrid cross, what is the genotypic ratio in F2 generation?
(a) 3:1
(b) 1:2:1
(c) 1:3:1
(d) 3:2:1
Answer: (b) 1:2:1
In simple words: When a simple cross (monohybrid) is done, and the second generation (F2) is formed, the genetic makeup (genotypic) ratio will be 1:2:1. This means you will have one pure dominant, two mixed, and one pure recessive genetic types.

🎯 Exam Tip: For a monohybrid cross in F2, the genotypic ratio is always 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive.

Genetics Very Short Answer Type Questions

Question 1. Define heredity.
Answer: Heredity is the process that deals with how characteristics and traits are passed from one generation to the next generation, ensuring continuity of features within a species. This is the biological transmission of genetic information.
In simple words: Heredity is about how features from parents, like eye color or height, are passed on to their children. It explains why family members look similar.

🎯 Exam Tip: Define heredity as the transmission of traits from parents to offspring, emphasizing the biological process of passing genetic information.

Question 2. Define variations.
Answer: Variations are the differences that can be observed among organisms of the same species. Even though they share basic features, individuals show unique differences in various traits, contributing to diversity.
In simple words: Variations are the small differences we see between living things of the same type. For example, some people have brown eyes and some have blue eyes.

🎯 Exam Tip: Emphasize that variations are the differences within a species and are crucial for evolution and adaptation.

Question 3. What is a trait?
Answer: A trait is a specific characteristic or feature that can be inherited from parents. These characteristics can be physical, like height or eye color, or behavioral, like certain habits. Traits are determined by genes.
In simple words: A trait is a special feature or quality that a living thing has, like being tall or having curly hair. These features are passed down from parents.

🎯 Exam Tip: Explain that a trait is any observable characteristic determined by genes.

Question 4. Name two human traits that show variations.
Answer: Two human traits that show variations are eye color and hair color. For example, eye color can range from blue to brown, and hair color can be black, brown, blonde, or red, showing great diversity within the human population.
In simple words: Two human features that are different among people are eye color and hair color. Everyone has eyes and hair, but the colors can be very different.

🎯 Exam Tip: When asked for examples, choose clear and easily observable human traits that exhibit polymorphism.

Question 5. What is a gene?
Answer: A gene is the basic unit of inheritance. It is a specific segment or part of a chromosome that contains instructions to control the appearance and expression of one or more hereditary characteristics in an organism. Genes are essentially the blueprints of life.
In simple words: A gene is like a tiny instruction book inside our bodies. It tells our body what features to have, like our eye color or how tall we grow. It's a small part of our DNA.

🎯 Exam Tip: Define a gene as the fundamental unit of heredity, a segment of DNA that codes for a specific trait or protein.

Question 6. What is genetics?
Answer: Genetics is the branch of biology dedicated to the study of heredity and the variations observed in living organisms. It explores how traits are passed down from parents to offspring and why individuals differ, from molecular to population levels.
In simple words: Genetics is the study of how living things get their features from their parents and why they are not exactly the same. It is the science of family traits and differences.

🎯 Exam Tip: Combine the definitions of heredity and variation to explain genetics as the study of both.

Question 7. What are hereditary traits?
Answer: Hereditary traits are specific characteristics that are transmitted or passed down from parents to their offspring across generations. These traits are encoded in an organism's genes and are the foundation of family resemblances.
In simple words: Hereditary traits are the features that children get from their parents, like the shape of their nose or their blood type. These features are passed on through families.

🎯 Exam Tip: Emphasize that hereditary traits are genetically determined and passed across generations.

Question 8. Mendel belonged to which country?
Answer: Gregor Mendel, the father of genetics, was from the country of Austria. This is where he conducted his famous experiments with pea plants.
In simple words: Gregor Mendel, the father of genetics, was from the country of Austria. This is where he did his famous experiments.

🎯 Exam Tip: Knowing the origin of key scientists helps contextualize their work within a historical framework.

Question 9. What is the scientific name of garden pea?
Answer: The scientific name for the garden pea, which Mendel used for his experiments, is *Pisum sativum*. This special name is used by scientists all over the world to identify the plant precisely.
In simple words: The scientific name for the garden pea, which Mendel used for his experiments, is Pisum sativum. This special name is used by scientists all over the world.

🎯 Exam Tip: Always provide the correct binomial nomenclature (Genus species) for scientific names, ensuring proper capitalization and italics.

Question 10. What are alleles?
Answer: Alleles are different forms of a gene that control a particular trait. For example, for the trait of height, there is an allele for tallness and an allele for shortness. They are also known as allelomorphs, representing variations in a gene.
In simple words: Alleles are like different versions of the same instruction. For example, for hair color, one allele might say "brown" and another might say "blonde."

🎯 Exam Tip: Define alleles as alternative forms of a gene, located at the same locus on homologous chromosomes.

Question 11. What do you understand by homozygous?
Answer: Homozygous refers to a genetic condition where an individual has two identical alleles for a particular gene. For instance, a pea plant could be homozygous tall (TT) or homozygous short (tt). This means both inherited copies of the gene are the same.
In simple words: Homozygous means having two of the exact same genes for one feature. Like having two instructions for "tall" or two for "short".

🎯 Exam Tip: Contrast homozygous (two identical alleles) with heterozygous (two different alleles) for clarity.

Question 12. What do you understand by heterozygous?
Answer: When an individual has two different forms (alleles) of a gene for a specific trait, this condition is called heterozygous. For example, 'Tt' for tallness and 'Yy' for yellow seeds represent heterozygous genotypes. In this case, the dominant allele's trait will usually be expressed.
In simple words: Heterozygous means having two different genes for one feature. For example, having one instruction for "tall" and one for "short" means the plant is heterozygous.

🎯 Exam Tip: Remember that in a heterozygous condition, the dominant allele typically expresses its phenotype.

Question 13. What is parental generation?
Answer: The parental generation, often denoted as the 'P' generation, refers to the initial set of organisms that are used in a genetic cross. These parents are typically purebred for the traits being studied and are bred to produce the first set of offspring.
In simple words: The parental generation is the first set of parents that are bred together in a genetics experiment. They are the original mother and father plants.

🎯 Exam Tip: Define the parental generation as the original pure-breeding individuals used to initiate a cross.

Question 14. What is F₁ generation?
Answer: The F₁ generation, also known as the first filial generation, consists of the first set of offspring produced directly from the cross of two parental generation organisms. These offspring typically inherit traits from both parents and often show only the dominant trait.
In simple words: The F₁ generation is the first group of children that come from the original parents. They are the first set of offspring from the breeding experiment.

🎯 Exam Tip: Explain that F1 stands for "first filial" and represents the immediate progeny of the parental cross.

Question 15. What is monohybrid cross?
Answer: A monohybrid cross is a genetic experiment specifically designed to study the inheritance pattern of only one pair of contrasting characters or traits. For example, crossing a tall pea plant with a short pea plant is a monohybrid cross, focusing solely on the height trait.
In simple words: A monohybrid cross is a type of breeding where scientists only look at one single feature, like height, at a time. It helps to understand how just that one feature is passed on.

🎯 Exam Tip: Emphasize that a monohybrid cross tracks the inheritance of a single gene or trait.

Question 16. What is dihybrid cross?
Answer: A dihybrid cross is a genetic experiment conducted to study the inheritance patterns of two different pairs of contrasting characters or traits simultaneously. For example, crossing a plant that has round yellow seeds with one that has wrinkled green seeds involves tracking two traits at once, like seed shape and seed color.
In simple words: A dihybrid cross is when scientists study two different features, like seed shape and seed color, at the same time. This helps to see how these two features are passed down together.

🎯 Exam Tip: Clearly state that a dihybrid cross involves the simultaneous inheritance of two distinct traits.

Genetics Short Answer Type Questions

Question 1. What term did Mendel use for genes? Where are the genes located?
Answer: Mendel used the term 'factors' to refer to what we now call genes. Genes are specific portions of DNA, which are located on chromosomes within the nucleus of a cell. These DNA segments carry the genetic code for producing a particular protein, influencing an organism's traits.
In simple words: Mendel called genes 'factors'. These 'factors' or genes are found on long strands of DNA inside the cell's control center, the nucleus. They hold the instructions for making different parts of the body.

🎯 Exam Tip: Remember that "factors" was Mendel's term before the concept of "genes" and DNA was fully developed. Genes are located on chromosomes.

Question 3. A true breeding tall plant is crossed with a true breeding short plant. All the off springs of the F₁ generation are tall. Of these two characters which one is dominant and which is reverse.
Answer: When a pure tall plant (TT) is crossed with a pure short plant (tt), all the plants in the F₁ generation are tall (Tt). This shows that the tall trait (T) is dominant, and the short trait (t) is recessive. Dominant traits are always seen when both types of genes are present.
In simple words: When a tall plant and a short plant are bred, all the baby plants are tall. This means 'tall' is the strong trait (dominant) and 'short' is the hidden trait (recessive).

🎯 Exam Tip: Focus on stating which trait is seen in the first generation (F₁) to identify dominance clearly.

Question 4. The tall plant of the F₁ generation with allele, Tt is selfed. What is the outcome or ratio of the F2 progeny?
Answer: When the F₁ generation tall plant (Tt) is selfed, it means a cross of Tt x Tt. The Punnett square below shows the possible genetic combinations for the F₂ progeny.

The outcome for the F₂ progeny is: 1 TT (pure tall), 2 Tt (hybrid tall), and 1 tt (pure short). This gives a phenotypic ratio of 3 Tall : 1 Short. The Punnett square helps visualize all possible gene combinations from the parents.
In simple words: When two tall plants from the first generation (that have both tall and short genes) breed together, their children will be tall and short. The table shows how their genes mix, giving 3 tall plants for every 1 short plant.

🎯 Exam Tip: Remember to clearly label parents, gametes, and the F₂ progeny genotypes and phenotypes for full marks when drawing a Punnett square.

Question 6. What is the difference between dominant and recessive traits?
Answer: A dominant trait is a characteristic that expresses itself in the F₁ generation. This means it masks the presence of any recessive allele. A recessive trait, however, does not express itself in the F₁ generation when a dominant allele is present but reappears in the F₂ generation when two hybrid parents are crossed. Many human traits, like eye color or handedness, also follow dominant and recessive patterns.
In simple words: A dominant trait is the one you see, even if there's another trait hiding. A recessive trait only shows up if there are two copies of it, otherwise, it stays hidden.

🎯 Exam Tip: Clearly explain how each trait is expressed in both F₁ and F₂ generations to show complete understanding.

Question 7. Make a Punnette square to show a cross between plants with yellow pod (Yy) and green pod (yy).
Answer: This cross is between a plant with yellow pods (Yy) and a plant with green pods (yy). The Punnett square for this cross is shown below:

From the Punnett square, the offspring will have a phenotypic ratio of 1 Yellow pod (Yy) : 1 Green pod (yy). This type of cross is often used to determine the unknown genotype of a dominant phenotype.
In simple words: We are mixing a plant with mixed yellow and green pod genes (Yy) with a plant that only has green pod genes (yy). The square shows all the possible baby plants, which will be half yellow pods and half green pods.

🎯 Exam Tip: Clearly label the gametes and use a Punnett square to show all possible genetic combinations in the offspring. Also, remember to state the expected phenotypic ratio.

Genetics Long Answer Type Questions

Question 1. (i) What is genetics?
(ii) Give the common name of the plant on which Mendel performed its experiments.
(iii) What for did Mendel use the term factors and what are these factors called now?
Answer:
(i) Genetics is the branch of biology that studies heredity and variation in living organisms. Understanding genetics helps us study how living things pass traits to their children.
(ii) Pea plant.
(iii) Mendel used the term 'factors' to describe the units that pass traits from parents to offspring. These factors are now called genes.
In simple words: Genetics is the study of how traits are passed down from parents. Mendel did his experiments on pea plants. He called the parts that carry traits "factors," which we now call genes.

🎯 Exam Tip: Remember the scientific name for the pea plant (Pisum sativum) to show a deeper understanding.

Question 2. How do Mendel's experiments show that the (a) traits may be dominant or recessive, (b) traits are inherited independently.
Answer:
(a) Mendel's experiments demonstrated dominant and recessive traits through his monohybrid crosses. When he crossed pure tall pea plants with pure dwarf pea plants, only tall plants were seen in the F₁ generation. This showed that the tall trait was dominant. When he self-pollinated the F₁ progeny, both tall and dwarf plants appeared in the F₂ generation in a 3:1 ratio. The reappearance of the dwarf trait in F₂ showed that it was recessive, remaining hidden in F₁.
(b) Mendel showed that traits are inherited independently through his dihybrid crosses. When he studied two pairs of contrasting characters (like seed color and seed shape) simultaneously, he found that the inheritance of one trait did not affect the inheritance of the other. The F₂ generation showed a phenotypic ratio of 9:3:3:1 for these two traits, indicating new combinations of traits that were not present in the parents. These simple experiments laid the foundation for modern genetics, helping scientists understand heredity.
In simple words: Mendel showed some traits are strong (dominant) and some are hidden (recessive) by seeing which traits appeared in the first and second generations of plants. He also showed that different traits, like plant height and seed color, are passed down separately, not always together.

🎯 Exam Tip: For part (a), describe the F₁ and F₂ generations and the reappearance of the recessive trait. For part (b), mention the dihybrid cross and the 9:3:3:1 ratio to illustrate independent inheritance.