Biology

Genetics and Plant Breeding

1,240 Questions

Genetics and Plant Breeding explores the principles of heredity, chromosomal inheritance, and hybridization techniques. It includes key concepts like Mendelian genetics, gene linkage, and polygenic inheritance. This topic is essential for students tackling advanced biology or botany sections in competitive examinations.

Mendelian InheritanceChromosome TheoryGene LinkagePolygenic InheritancePlant HybridizationPopulation Genetics Equilibrium

Genetics and Plant Breeding Questions

Multiple choice botany heredity: from parents to offsprings experiments of mendel mendel's law of inheritance works of mendel

Which law would have been violated if Mendel had chosen eight characters in garden pea?

  1. Law of dominance

  2. Law of segregation

  3. Law of independent assortment

  4. Law of purity of gametes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pea plant has 2n= 14. Mendel chose 7 characters the genes for which are present on 7 different chromosomes. The presence of different chromosomes allowed genes for two traits to assort independently during dihybrid cross and recombinant progeny, as well as parental progeny, is produced. If he had chosen eight characters, genes for any two characters must be present on the same chromosome and would exhibit linkage and the law of independent assortment is violated. Law of dominance explains the appearance of a dominant trait by heterozygous genotype and law of segregation tells about segregation of alleles of heterozygous genotype during gamete formation. Law of purity tells about the presence of a single allele of a gene in gametes. Thus, the correct answer is option C.

Multiple choice botany heredity: from parents to offsprings experiments of mendel mendel's law of inheritance works of mendel

Which one of the following is not one of Mendel's laws?

  1. Law of dominance

  2. Law of segregation

  3. Law of incomplete dominance

  4. Law of independent assortment
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Laws of Mendel:
  • Mendel's Law of Dominance states that recessive alleles will always be masked by dominant alleles. Therefore, a cross between a homozygous dominant and a homozygous recessive will always express the dominant phenotype, while still having a heterozygous genotype.
  • The law of segregation states that during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent.
  • The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. Independent assortment of genes and their corresponding traits was first observed by Gregor Mendel in 1865 during his studies of genetics in pea plants.
Multiple choice botany heredity: from parents to offsprings experiments of mendel mendel's law of inheritance works of mendel

If a plant is heterozygous for tallness, the ${F _2}$ generation has both tall and dwarf plants. This proves the principle of

  1. Dominance

  2. Segregation

  3. Independent assortment

  4. Incomplete dominance
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • According to the law of dominance, a trait is represented by two contrasting factors of a gene in a heterozygous individual; only dominant trait is expressed, irrespective of the presence of both factors, in a heterozygous individual.
  •  It does not tell about the reappearance of the missing trait in $F _2$ generation. The law of segregation states that the two factors for a trait, present together in a heterozygous individual, do not get mixed and are separated during gametogenesis. 
  • Thus each gamete receives one allele for a trait and two types of gametes are formed; 50% gametes carry factor for dominance and 50% carry the recessive factor. Random fusion of these gametes leads to the presence of both recessive and dominant individuals in $F _2$ generation. 
  • Law of independent assortment tells about segregation and distribution of factors governing two different traits; not about segregation of factors of one trait. Incomplete dominance is the condition when none of the factors of a gene is dominant and the phenotype of a heterozygous dominant individual is a blend of dominant and recessive traits. 
  • It affects the phenotype of $F _1$ individuals, not that of $F _2$. Thus, the correct answer is option B.
Multiple choice botany heredity: from parents to offsprings experiments of mendel mendel's law of inheritance works of mendel

Mendel enunciated principles of inheritance

  1. Two

  2. Three

  3. Four

  4. Five
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gregor Johann Mendel, an Austrian Monk, discovered the principles of heredity through the experiments on the pea plant. Mendel conducted hybridization experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. They are the Law of dominance, Law of segregation, Law of Independent assortment.

So, the correct option is ‘Three’.

Multiple choice botany heredity: from parents to offsprings experiments of mendel mendel's law of inheritance works of mendel

What is the blending theory of inheritance?

  1. Mendels theory of how the traits of parents are passed to offspring through the gametes

  2. Darwins theory of how traits are passed from all parts of the parents body into the gamete to be transmitted to the offspring

  3. The modern theory of how genetic information is passed from parents to offspring

  4. An old theory that said that offspring show traits intermediate between those of the parents
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The blending theory state that the inheritance of traits from two parents produces offspring with characteristics that are intermediate between those of the parents.

So, the correct option is 'An old theory that said that offspring show traits intermediate between those of the parents'.

Multiple choice biology mendel's law of inheritance experiments of mendel works of mendel mendel's laws of inheritance

Choose the incorrect pair among the Mendel choose for his experiments.

  1. Pod shape - Elongated/constricted

  2. Seed color - Yellow/green

  3. Seed shape - Round/wrinkled

  4. Flower position - Axial/terminal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The incorrect pair here is the contrasting feature of the pod shape is "Elongated/constricted" which should be smooth/constricted in reality.

Multiple choice botany unravelling genetic mysteries experiments of mendel mendel's law of inheritance works of mendel

Which of the following characteristics represent inheritance of dihybrid crosses in pea :
a) Incomplete dominance
b) Dominance
c) Law of segregation 
d) Co - dominance
e) Polygenic inheritance
f) Law of independent assortment 

  1. b and f

  2. a, d and f

  3. b, c and f

  4. b , c and e
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A dihybrid cross involves the inheritance of two traits. Mendel's experiments with dihybrid crosses demonstrated the Law of Dominance (b) and the Law of Independent Assortment (f).

Multiple choice biology mendel's law of inheritance experiments of mendel works of mendel mendel's laws of inheritance

The main reason for the success of Mendel was that

  1. He made statistical analysis of the offsprings.

  2. He first took only one character at a time in his crosses.

  3. He kept pedigree records.

  4. He selected pea plants.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Main reasons for the success of Gregor Mendel: 

1. Mendel concentrated in one or few characters at a time.
2. He made controlled crosses and kept careful numerical records of the results.
3. He suggested 'factors' as a cause of characters.
4. The experimental material Pisum sativum was a wise choice.

Multiple choice biology mendel's law of inheritance experiments of mendel works of mendel mendel's laws of inheritance

Correct reason of Mendel's success was

  1. He repeated each experiment several times.

  2. Traits chosen by him had genes far apart so that linkage was absent.

  3. He kept record of all experiments.

  4. He used statistical techniques.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mendel chose seven pairs of contrasting traits, the gene for each of which is present on seven different chromosomes of pea plant. Due to the presence on different chromosomes, Mendel's trait followed independent assortment during meiosis and produced the expected parental and recombinant phenotypes. If genes of these traits would have present together showing linkage, Mendel would not have got the expected results. Repeating the experiment, keeping records and use of statistical analysis were the secondary factors; major being the chosen traits not showing linkage. 

So, the correct answer is 'Traits chosen by him had genes far apart so that linkage was absent'.

Multiple choice biology mendel's law of inheritance experiments of mendel works of mendel mendel's laws of inheritance

Mendel was lucky, because

  1. He was born in Austria which is a nice country.

  2. He used pea plant for his experiment which is rich in protein.

  3. The genes for different characters are located on different chromosomes in Pisum sativum.

  4. The Pisum sativum is short-lived plant.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mendel was lucky because he used pea plant i.e. Pisum sativum, they are bisexual, they had pure breeding varieties with observable characters, & each character is regulated by one type of gene, whether it is tall, dwarf, round or wrinkled etc. It was an ideal choice for him.

So, the correct answer is "The genes for different characters are located on different chromosomes in Pisum sativum".

Multiple choice biology mendel's law of inheritance experiments of mendel works of mendel mendel's laws of inheritance

When two genes control a single character and have cumulative effect the ratio is _______

  1. $1:1:1:1$
  2. $1:4:6:4:1$
  3. $1:2:1$
  4. $1:6:15:20:15:6:1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
When two genes present on the same loci give an additive or cumulative effect like the spotted and Dotted seed of Lens sps the ratio is 1:2:1
So, the correct answer is '1:2:1'
Multiple choice botany unravelling genetic mysteries experiments of mendel mendel's law of inheritance works of mendel

Successive exploitation of heterocyst depends upon the ______________.

  1. Presence of heterotic effect in the hybrid

  2. Availability of male sterility

  3. Out crossing nature of the flower

  4. Heterotic effect and availability
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The success of hybrid seed production often relies on the heterotic effect (hybrid vigor), which is the tendency of a crossbred individual to show qualities superior to those of both parents.

Multiple choice botany unravelling genetic mysteries experiments of mendel mendel's law of inheritance works of mendel

If mendel had studied the 7 traits using a plant with 12 chromosomes instead of 14 ,in what way this interpretation have been different 

  1. He would have mapped the chromosomes

  2. He would have discovered blending or incomplete dominance

  3. He would not have discovered law of independent assortement

  4. He would have discovered sex linkage
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice botany unravelling genetic mysteries experiments of mendel mendel's law of inheritance works of mendel

Choose the correct answer from the alternatives given.

Among the seven pairs of contrasting traits in pea plant as studied by Mendel, the number of traits related to flower, pod, and seed respectively were

  1. 2, 2, 2

  2. 2, 2, 1

  3. 1, 2, 2

  4. 1, 1, 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mendel's seven traits were: flower color, flower position, stem height, pod shape, pod color, seed shape, and seed color. Categorizing these: flower (2), pod (2), and seed (2), with stem height as the remaining one.