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

Which one of the following is the main cause of the lower yield of F2 generation than the F1 generation following hybridization between two inbred lines of maize?

  1. Heterosis

  2. Luxuriance

  3. Inbreeding depression

  4. Heterobeltiosis
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When two inbred maize lines are crossed, the F1 generation exhibits heterosis (hybrid vigor), resulting in superior yield and performance. However, when F1 plants are self-pollinated to produce F2, this heterosis is largely lost due to segregation and recombination of alleles, leading to inbreeding depression. The F2 generation shows increased homozygosity and reduced performance compared to the F1 hybrid.

Multiple choice

Assertion (A) : The expression of each gene is independent of the other genes.

Reason (R) : Genes follow the law of independent assortment as per Mendel's studies.

  1. Both A and R are individually true and R is the correct explanation of A.

  2. Both A and R are individually true but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

  Genes donot follow the law of independent assortment as per Mendel's studies.

Multiple choice

Match List I (Phenotypic segregation ratio) with List II (Type of gene action) and select the correct answer using the codes given below the lists ||| |---|---| | List I | List II | | A. 9 : 6 : 1 | 1. Duplicate gene action | | B. 12 : 3 : 1 | 2. Supplementary gene action | | C. 9 : 3 : 4 | 3. Inhibitory gene action | | D. 13 : 3 | 4. Masking gene action | | | 5. Polymeric gene action |

  1. A-3 B-2 C-1 D-5

  2. A-5 B-2 C-1 D-3

  3. A-5 B-4 C-2 D-3

  4. A-3 B-4 C-2 D-5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

9:6:1 is duplicate gene action (two genes with similar effects), 12:3:1 is supplementary gene action (dominant allele at one locus masks expression at another), 9:3:4 is inhibitory gene action (one gene inhibits another), 13:3 is suppressor gene action (one gene suppresses another). The correct matching is A-5, B-4, C-2, D-3.

Multiple choice

A male, homozygous dominant black dog is mated with a homozygous recessive brown bitch. The black genotype is BB, the brown genotype is bb. The offsprings will be

  1. all brown

  2. all black

  3. 50% black and 50% brown puppies

  4. intermediate in colour
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

All the male gametes will carry the dominant allele B. The female gametes will carry the recessive allele b. This means that the genotype of all the puppies will be Bb. Since the allele for black is dominant, all the puppies will be black.

Multiple choice

A pure breeding male black dog is mated with a female brown bitch and they produce a litter of 12. The allele for black fur is dominant to the allele for brown fur. What is the expected distribution of colour and sex in their litter?

  1. 6 brown females and 6 black males

  2. 7 black and 5 brown, all male

  3. 6 black males and 6 black females

  4. 12 black males
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct answer. The pure breeding male’s genome must be BB and the brown bitch’s genome must be bb. The allele for black fur is dominant over the brown allele. Therefore, all the offsprings will be black (Bb). The dog carries the X and Y chromosomes. The bitch carries two X chromosomes. At meiosis, only one of each chromosome pairs goes to the gametes.

Multiple choice

What do you call the crossing that involves plants of same variety?

  1. Intravarietal hybridization

  2. Interspecific hybridization

  3. Intervarietal hybridization

  4. Intrageneric hybridization
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Intravarietal hybridization involves crossing plants within the same variety. This is different from intervarietal (between varieties) or interspecific (between species) hybridization.

Multiple choice

In reciprocal recombination,

  1. recombination occurs between two genes with high sequence identity

  2. recombination occurs between two DNA sequences with little or no sequence identity

  3. a symmetrical exchange of genetic material occurs between two DNA strands

  4. specialized nucleotide sequences exhibiting some degree of target site specificity are moved between non-homologous sites within a genome

  5. offspring are produced with combinations of traits that differ from those found in either parent
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In site-specific recombination, specialized nucleotide sequences exhibiting some degree of target site specificity are moved between non-homologous sites within a genome.

Multiple choice

Consider the following statements:

(1) Genome is a complete set of an organism's heredity information. (2) Triticale, a crop species has been developed through hybridisation between Wheat and Rye.

Which of the given statements is/are correct?

  1. Only (1)

  2. Only (2)

  3. Both (1) and (2)

  4. Neither (1) nor (2)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement (1) is correct. A genome is the complete collection of hereditary information for an individual organism. Statement (2) is also correct. Triticale is a crop species resulting from a plant breeder's cross between wheat (Triticum) and rye (Secale).