RBSE Solutions For Class 10 Science Chapter 3: Genetics | Textbook Important Questions & Answers

The branch of biology which deals with the study of heredity and variation is called genetics. RBSE Class 10 solution of Science Chapter 3 is helpful for students to grasp the basics concepts and lay a strong foundation for the subject Science. These solutions can be used by the students not only to find the right method but also for verifying if their answers are correct or not. Helping the students to understand the topics and concepts comprehensively is the ultimate aim of providing the perfect RBSE Solutions.

By going through the solutions, students will get to know a better way of representing their answers, which will help them in scoring high marks in the annual exam. Whenever students find themselves stuck somewhere, they can refer to these RBSE Class 10 Science Chapter 3 solutions.

Students can also get all subjects Class 10 solutions for Rajasthan Board here.

RBSE Class 10 Science Chapter 3: Objective Textbook Questions and Solutions

Q1. Who coined the term ‘genetics’?

(A) Mendel

(B) Bateson

(C) Morgan

(D) Punette

Answer: B

Q2. Experiments of Mendel were on?

(A) Sweet pea

(B) Wild pea

(C) Garden pea

(D) All of these

Answer: C

Q3. Study of heredity and variation is called.

(A) Heredity

(B) Geology

(C) Forestry

(D) None of the above

Answer: A

Q4. Green colour of pea pod is which type of character?

(A) Dominant

(B) Recessive

(C) Incomplete dominance

(D) Codominance.

Answer: A

Q5.Usually number of alleles of a gene are?

(A) Four

(B) Three

(C) Two

(D) One

Answer: C

Q6. Mendel selected how many inheritable pairs of traits for his experiments?

(A) 34

(B) 2

(C) 12

(D) 7

Answer: D

Q7. When F1 generation is crossed with anyone parent, then it is called?

(A) Reciprocal cross

(B) Test cross

(C) Back cross

(D) All of these

Answer: C

Q8. Ratio of offspring from Tt x tt cross is?

(A) 3: 1

(B) 1: 1

(C) 1 : 2 : 1

(D) 2 : 1

Answer: B

Q9. Which contrasting character was not selected by Mendel for his experiment

(A) Colour of root

(B) Colour of flower

(C) Colour of seed

(D) Colour of pod

Answer: A

Q10. How many genotypes formed in F2 generation of monohybrid cross

(A) 2

(B) 3

(C) 4

(D) 9

Answer: B

RBSE Class 10 Science Chapter 3: Very Short Answer Type Questions and Solutions

Q11. Who is called father of genetics?

Answer: The father of genetics is Mendel

Q12. Which plant was selected by Mendel for his experiments?

Answer: Mendel selected Pea plant for his experiments.

Q13. What is dominant character?

Answer: A character which expresses itself in generation is called dominant character.

Q14. Which is known as the transmission of genetic characters from one generation to another generation?

Answer: Inheritance is known as the transmission of genetic characters from one generation to another generation.

Q15. Who discovered Mendel’s Law?

Answer: Hugo de Vries, Carl Correns and Erick von Tschermak.

Q16. What is the full name of Mendel?

Answer: Gregor John Mendel

Q17. Write the names of laws proposed by Mendel.

Answers: The laws proposed by Mendel are as follows:

  • Law of dominance
  • Law of segregation
  • Law of independent assortment

Q18. What is test cross?

Answer: When F1 generation is crossed with recessive then it is called as test cross.

Q19. What do you understand by out cross.

Answer: When F1 generation is crossed with its parent’s generation with dominant traits it is called out cross.

Q20. Which law of Mendel cannot be explained by monohybrid cross?

Answer: Law of independent assortment law of Mendel cannot be explained by monohybrid cross

RBSE Class 10 Science Chapter 3: Short Answer Type Questions and Solutions

Q21. What is the difference between phenotype and genotype?

Answer: Phenotype – External appearance of an individual is called phenotype. Eg: Tall plant which genotypically may be homozygous (TT) or heterozygous (Tt).

Genotype – Genetic constitution of an individual is called genotype. Eg: Pure or homozygous (TT) or heterozygous (Tt).

Q22. Explain the dihybrid cross.

Answer: Dihybrid cross – Such type of cross in which two contrasting characters (Traits) are considered is called dihybrid cross.

Q23. Write the reasons of successfulness of Mendel?

Answer: Following are the reasons for success of Mendel:

  • Mendel studied the inheritance of one character at a time.
  • Mendel maintained the statistical record of the experiments and analysed them carefully.
  • Mendal selected the plant material for his experiments carefully.

Q24. Why did Mendel select pea plant for his experiments?

Answer: Mendel selected pea plants for his experiments due to following reasons:

  • Pea plant is annual, therefore, it was possible to study many generations in a short duration.
  • It was easy to get pure line of homozygous plants by self pollination because of bisexual flowers.
  • Artificial cross pollination can be easily done by emasculation technique.
  • Various contrasting characters are present in pea plants.

Q25. Write a brief life introduction of the Mendel.

Answer: Gregor Johann Mendel is called father of genetics because Mendel proposed the laws of inheritance in plants for the first time. Mendel was born on 22 July 1822 in Silision village of Heizendarf province in Austria. In 1842, after receiving a degree in philosophy, he became a priest in the church at Brunn in Austria. He began his study on garden pea in church’s garden and continued his studies for seven years. He presented his findings in the form of research paper in front of Brunn Society of Natural History. His paper was published in the annual magazine of the society.

Q26. Explain the Mendel’s Law of Dominance.

Answer: According to this law, when a cross takes place in between homozygous contrasting plants, the character which express itself in F1 generation is called dominant and the character which does not express itself in F1 generation is called recessive. Example: When a pure or homozygous tall (TT) plant is crossed with pure or homozygous dwarf (tt) plant then in F1 generation all plants (100%) were tall (Tt).

Q27. Write the importance of Mendel’s laws of inheritance.

Answer: Mendel proposed some important laws through hybridization experiments on garden pea, which are called Mendel’s Law of Inheritance. These laws are follows:

  • Law of dominance.
  • Law of segregation or law of purity of gametes.
  • Law of independent assortment.

Q28. Difference between homozygous and heterozygous.

Answer:

Homozygous Heterozygous
Homozygous consists of two copies of the same allele that codes for a particular trait. Heterozygous consists of two different copies of alleles that code for a particular trait.
Consist of either dominant or recessive allele pairs but not both Consist of both dominant and recessive allele pairs
Self-breeding results in the same traits over generations Self-breeding results in the combination of traits
Produces a single gamete Produces two types of gametes
The two types of homozygous alleles are homozygous-dominant and homozygous-recessive The three types of heterozygous alleles complete dominance, incomplete dominance, and codominance

Q29. What is genetics? Who coined the term genetics?

Answer: The exploration of the working and major codes of variation and heredity is termed as Genetics. The groundwork on which heredity stands is known as inheritance. It is defined as the procedure by which characteristics are handed down from one generation to the other. Gregor Johann Mendel is known as the “Father of Modern Genetics” for his discoveries on the basic principles of heredity. The term genetics was coined by Bateson.

Q30. What is back cross? Define test cross and out cross.

Answer: When generation is crossed with any one of both the parents called as back cross. It is of two types.

Out Cross – If F1 generation (Tt) is crossed with dominant parent (TT) called as out cross. The offspring obtained from this cross were all tall plants, out of these 50% were homozygous tall (TT) and 50% were heterozygous tall (Tt) plants.

Test Cross – When generation is crossed with recessive then it is called as test cross. The phenotypic and genotypic ratio of offspring obtained from this cross was same i.e. 1:1. 50% heterozygous tall (Tt) and 50% homozygous dwarf (tt) plants are obtained.

Q31. Why was Pea Plant Selected for Mendel’s Experiments?

Answer: Mendel selected a pea plant for his experiments:

  1. The pea plant can be easily grown and maintained.
  2. They are naturally self-pollinating but can also be cross-pollinated.
  3. It is an annual plant, therefore, many generations can be studied within a short period of time.
  4. It has several contrasting characters.

Mendel conducted 2 main experiments to determine the laws of inheritance. These experiments were:

  1. Monohybrid Cross Experiment
  2. Dihybrid Cross Experiment

While experimenting, Mendel found that certain factors were always being transferred down to the offsprings in a stable way. Those factors are now called genes i.e. genes can be called as the units of inheritance.

Q32. Explain key points on Mendel’s experiment.

Answer: Key Points on Mendel’s Laws are as follows.

  • The law of inheritance was proposed by Gregor Mendel after conducting experiments on pea plants for seven years.
  • The Mendel’s laws of inheritance include law of dominance, law of segregation and law of independent assortment.
  • The law of segregation states that every individual possesses two alleles and only one allele is passed on to the offspring.
  • The law of independent assortment states that the inheritance of one pair of genes is independent of inheritance of another pair.

Q33. What are dominant and recessive traits?

Answer: When Mendel crossed one tall and one short pea plant, all the offsprings (F1 generation) were tall. When he self-crossed the F1 generation, among them 3/4th of the progenies were tall whereas 1/4th were short. Thus he concluded that although the F1 progeny had both tall and short traits, only tall plants were observed in the F1 generation, this means that tallness is a dominant trait.

Q34. Discuss the main aim of Mendel’s experiments?

Answer: The main aim of Mendel’s experiments was:

  • to determine whether the traits would always be recessive.
  • whether traits affect each other as they are inherited.
  • whether traits could be transformed by DNA.

Q35. State the universally accepted law of inheritance?

Answer: Law of segregation is the universally accepted law of inheritance. It is the only law without any exceptions. It states that each trait consists of two alleles which segregate during the formation of gametes and one allele from each parent combines during fertilization.

Q36. Explain the difference between Difference Between Monohybrid And Dihybrid.

Answer:

Properties Monohybrid Dihybrid
Means Mono refers to single and hybrid means mixed breed Di refers to two or double and hybrid means breed
Cross Monohybrid cross is used to study the inheritance of a single pair of alleles Dihybrid cross is used to study the inheritance of 2 different alleles
Used to study the dominance of genes Offspring assortment
Genotype ratio 1:2:1 1:2:1:2:4:2:1:2:1
Phenotype ratio 3:1 9:3:3:1
Ratio cross test -1:1 -1:1:1:1

Q37. Explain Monohybrid ratio and Dihybrid ratio?

Answer: The ratio obtained from monohybrid cross is called monohybrid ratio. The ratio obtained from dihybrid cross is called dihybrid ratio.

Q38. What is hybridization?

Answer: The process of crossing genes or different genotype of two organisms is known as hybridization.

  • Genotype: Genotype is the set of genes found in an individual. Ex: Genes responsible for colour of eye, complexion etc.
  • Phenotype: Phenotype is the all observable or expressed characteristics in an individual. Ex: Tallness or shortness, color of eyes etc.

Q39. Explain two laws of inheritance?

Answer: Law of Dominance – Distinct elements termed as factors control the characteristics. These factors at all times exist as a couple. One of the constituent genes of the couple dominates over the former.

Law of Segregation – Alleles don’t blend and the two characteristics are recuperated all through the gamete formation (in the F2 generation). The characters apart from each other and pass on to diverse gametes. Comparable types of gametes are produced by Homozygous and heterozygous produces diverse sorts of a gamete with varied characteristics.

RBSE Class 10 Science Chapter 3: Essay Type Questions and Solutions

Q40. Explain the Mendel’s Law of Segregation with example.

Answer: Law of Segregation – Mendel’s law of segregation states that:

During the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene. Example: If homozygous tall (TT) plant is crossed with homozygous dwarf (tt) plant then in F1 generation all plants were hybrid or heterozygous tall (Tt). In heterozygous condition, both alleles are not contaminated with one another, at the time of gamete formation both alleles segregate from each other and enter in different gametes. Due to this segregation dwarfism (tt) character reappear again in F2 generation phenotypic ratio obtained from F2 generation is 3:1 and the genotypic ratio is 1:2:1.

Law of segregation is the second law of inheritance. This law explains that the pair of alleles segregate from each other during meiosis cell division (gamete formation) so that only one allele will be present in each gamete.

In a monohybrid cross, both the alleles are expressed in the F2 generation without any blending. Thus, the law of segregation is based on the fact that each gamete contains only one allele.

This law is based on four basic concepts:

  • A gene exists in more than one form of an allele.
  • When gametes are produced by meiosis, the allelic pairs separate leaving each gamete with a single allele.
  • Every organism inherits two alleles for each trait.
  • The two alleles of a pair are different, i.e., one is dominant and one is recessive.

RBSE Class 10 Science Chapter 3 - 40

Q41. What is Mendelism? Explain law of independent assortment in detail.

Answer: The Laws of inheritance were derived on the basis of finding by Mendel. These laws are collectively known as Mendelism.

According to the law of independent assortment, the alleles of two more genes get sorted into gametes independent of each other. The allele received for one gene does not influence the allele received for another gene. Mendel’s experiment always portrayed that the combinations of traits of the progeny are always different from their parental traits. Based on this, he formulated the Law of Independent Assortment.

Mendel’s Experiment on Law of Independent Assortment

The Law of Independent Assortment states that during a dihybrid cross (crossing of two pairs of traits), an assortment of each pair of traits is independent of the other. In other words, during gamete formation, one pair of trait segregates from another pair of traits independently. This gives each pair of characters a chance of expression.

In the dihybrid cross, he chose round-yellow seed and wrinkled green seed and crossed them. He obtained only round yellow seeds in the F1 generation. Later, self-pollination of F1 progeny gave four different combinations of seeds in the F2 generation. He obtained round-yellow, wrinkled-yellow, round green and wrinkled green seeds in the phenotypic ratio 9:3:3:1.

The phenotypic ratio 3:1 of yellow: green colour and the ratio 3:1 of the round: wrinkled seed shape during monohybrid cross was retained in the dihybrid cross as well. Thus, he concluded that characters are distributed independently and inherited independently. Based on this observation, he developed his third law – Law of Independent Assortment.

The dihybrid crosses between the parental genotype RRYY (round yellow seeds) and rryy (green wrinkled seeds) explains the law. Here the chances of formation of gametes with the gene R and the gene r are 50:50. Also, the chances of formation of gametes with the gene Y and the gene y are 50:50. Thus, each gamete should have either R or r and Y or y.

The Law of Independent Assortment states that the segregation of R and r is independent of the segregation of Y and y. This results in four types of gametes RY, Ry, rY, and ry. These combinations of alleles are different from their parental combination (RR, YY, rr and yy).

Q42. Explain the Mendel’s Law of Inheritance?

Answer: Mendel proposed some important laws through hybridization experiments on garden pea, which are called Mendel’s law of inheritance. These laws are follows:

  • Law of dominance
  • Law of segregation or Law of purity of gametes
  • Law of independent assortment.

Law of Dominance

This is also called Mendel’s first law of inheritance. According to the law of dominance, hybrid offsprings will only inherit the dominant trait in the phenotype. The alleles that are suppressed are called as the recessive traits while the alleles that determine the trait are known as the dormant traits.

Law of Segregation

The law of segregation states that during the production of gametes, two copies of each hereditary factor segregate so that offspring acquire one factor from each parent. In other words, allele (alternative form of the gene) pairs segregate during the formation of gamete and re-unite randomly during fertilization. This is also known as Mendel’s third law of inheritance.

Law of Independent Assortment

Also known as Mendel’s second law of inheritance, the law of independent assortment states that a pair of trait segregates independently from another pair during gamete formation. As the individual heredity factors assort independently, different traits get equal opportunity to occur together.

Q43. Explain importance of Mendel’s Law of Inheritance.

Answer: The importance of Menedel’s Law of Inheritance are:

  • It is important to find dominant character in living organisms because many harmful and lethal recessive genes are not able to express themselves in the presence of dominant gene.
  • Gene concept was proved by Mendel’s law of segregation.
  • According to the law of segregation one gene has two alleles and they control two contrasting characters.
  • With the help of Mendel’s law, we know about the new characters develop in hybrid offspring.
  • Useful characters can be brought into species and harmful characters can be removed by the method of hybridisation.
  • With the help of Mendel’s laws disease resistant and high yielding varieties of crop plants can be developed.
  • A branch of Science Eugenics related with the improvement of human race is based on Mendel’s laws.

Q44. Discuss how Mendel’s experiments show that traits are inherited independently?

Answer: Mendel was successful in showing that traits were inherited independently with the help of pea plants. He chose two different pea plants that had following traits:

  • Pea shape: Round or wrinkled
  • Pea colour: Yellow or green
  • Flower colour: Purple or white
  • Flower position: Terminal or axial
  • Plant height: Tall or short
  • Pod shape: Inflated or constricted
  • Pod colour: Yellow or green

Following are the principles of inheritance that were developed based on Mendel’s experiments:

  • Fundamental theory of heredity: According to the theory, offspring have their genes inherited from their parents.
  • Principle of segregation: It was studied that during reproduction, the factors determining the traits get separated into reproductive cells and this process is known as meiosis and reunite during fertilization.
  • Principle of independent assortment: Different chromosomes have different genes located on them that can be inherited independently of each other.

Therefore, the result of his experiment when he crossed a pea plant with yellow colour, round seed with green colour wrinkled seed were two parental and two recombinant phenotype. The parental were yellow, round and green wrinkled. While the recombinant were yellow wrinkled and green round. This result explains that the traits are separate from their parental combinations and are inherited independently.

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