Genetics & Plant Breeding Test - 1

The correct answer is 12 : 3 : 1.

• When the interaction occurs between different pairs of alleles influencing a character of an individual is said to be interallelic interaction or epistatic.
• The gene that has masking effect is called epistatic gene, and the gene whose effect is masked is known as hypostatic gene.
• Epistasis leads to modification of normal di-hybrid or tri-hybrid segregation ratio in F2 generation.
• The term epistasis was coined by Bateson in 1909.
• Various types of epistatic gene interaction are:

1. Recessive epitasis (9 : 3 : 4)
2. Dominant epistasis (12 : 3 : 1)
3. Dominant and recessive (inhibitory) epistasis (13 : 3)
4. Duplicate recessive epistasis (9 : 7)
5. Duplicate dominant epistasis (15 : 1)
6. Polymeric gene interaction (9 : 6 : 1)

The correct answer is Carrot.

Key Points

• Carrot, alfalfa and Lucerne show very high Inbreeding Depression. 
• Jowar, Maize and Bajra etc., show moderate Inbreeding Depression.
• Onion, many Cucurbits, Rye and Sunflower, etc. show a small degree of Inbreeding Depression
• The self-pollinated species do not show Inbreeding Depression, although they do show heterosis
• In cross-pollinated crops and in asexually propagated species inbreeding has harmful effect which are severe.

Additional Information Inbreeding:

• Inbreeding or consanguineous mating is mating between individuals related by descent or ancestry.
• When the individuals are closely related, e.g., in brother-sister mating or sib mating, the degree of inbreeding is high.
• The highest degree of inbreeding is achieved by selfing.
• The chief effect of inbreeding is an increase in homozygosity in the progeny, which is proportionate to the degree of inbreeding.

Inbreeding depression:

• Inbreeding depression may be defined as the reduction or loss in vigour and fertility as a result of inbreeding.
• Inbreeding depression = {(F1-F2) / F1} x 100
• In 1876, Darwin published his book on cross and self fertilization in vegetable kingdom and concluded that progeny obtained from self fertilization were weaker than those obtained from out crossing
• Inbreeding depression is categorised into 4 categories; they are High Inbreeding depression, Moderate Inbreeding depression, Low inbreeding depression, and Lack of Inbreeding depression.

The Correct answer is All are tall.

Key Points

•  In a monohybrid test cross, involving a heterozygous tall plant (Tt) and a pure dwarf plant, the progeny consists of tall and dwarf plants in the ratio of 1:1.
•  In F1 generation, both progenies should be tall.
•  In F2 generation, progenies should be tall and dwarf in the ratio of 75:25.

Additional Information

• Father of Genetics: Gregor Mendel 
• He discovered the fundamental laws of inheritance and hybridization.
• He deduced that genes come in pairs and are inherited as distinct units, one from each parent.
• Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.

The correct answer is Remain the same.

Key Points

• A cell divides once into two identical daughter cells is called Mitosis. 
• It will have the same number and kind of chromosome as the parent nucleus
• Mitosis is seen in the growth and repair cells.

Additional Information

•  A cell divides twice to produce four daughter cells carrying half the genetic information is called meiosis.
• Meiosis is seen in sperm and egg cells.​

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The correct answer is Bt. Brinjal.

• Bacterial genes are functional units of DNA that have their effects through a diffusible product. The final product may be an RNA molecule, or the RNA intermediate may be translated into protein, which then exerts the effect.
• The effect of the gene is manifested in a phenotype, an observable property of the organism.

Key Points

• Bt.Brinjal is Bacillus Thuringiensis Brinjal. It is a genetically modified Brinjal.
• It is developed to give resistance to insects called lepidopteron. It is a very dangerous pest of Brinjal.
• The resistant gene is taken from the soil bacterium called Bacillus Thuringiensis.
• The gene for Cry 1 Ac is taken and inserted into the cultivars by the agrobacterium mediated gene transfer method.

Additional Information

The correct answer is Agrobacterium tumefaciens.

Key Points

• Agrobacterium tumefaciens
  • Agrobacterium tumefaciens has extensive usage in genetic engineering work in plants.
  • It is a soil-borne, plant pathogenic bacterium that causes tumorous growths.
  • It has the ability to transfer a particular type of DNA segment (T-DNA).
  • It induces the tumour-inducing plasmid (Ti) into the infected cells.
  • It is integrated into the host genome and transcribed, causing the crown gall disease.

Additional Information

• Clostridium septicum
  • It is a gram-positive, rod-shaped bacterium.
  • It is a spore-forming, obligate anaerobic bacteria.
  • It is one of several bacteria responsible for myonecrosis or gas gangrene. It is associated with malignancy.
• Xanthomonas citri
  • It is a gram-negative, rod-shaped proteobacterium.
  • It is a phytopathogen that is harmless for humans.
  • Phytopathogen is the causing agent of citrus canker, a disease that affects citrus fruits.
• Bacillus coagulens
  • It is an endospore that produces lactic acid.
  • It forms soil bacteria that are used as probiotics.
  • It is similar to lactobacillus.

The correct answer is Heterozygous.

Explanation:

• Hybridization means mating or crossing two plants or lines of dissimilar genotypes.
• The seeds as well as the progeny resulting from the hybridization are known as hybrid or F1.
• A hybrid is always Heterozygous.
• The progeny of F1 obtained by self or intermating of F1 plants and the subsequent generations are called segregating generations.
• Hybridization is the most common method of crop improvement and the majority of the crop varieties have originated from hybridization.
• One of the objectives of hybridization is to create genetic variation.
• Two genotypically different plants are crossed together to obtain F1 generation.
• F1 is advanced to generate F2 generation.
• The degree of genetic variation in F2 and subsequent generation depend on a number of heterozygous genes in F1.

Additional Information

Types of Hybridization:

Inter-varietal / Intraspecific Hybridization 

• Parents involved in hybridization belong to the same species.
• They may be two strains, varieties or races.
• Varietal crosses may be simple crosses or complex crosses

a. Simple crosses: Two parents are crossed to produce F1 (A XB).

b. Complex crosses: More than two parents are crossed to produce the hybrid (AXB) X C X F1.

The correct answer is Quantitative character.

Key Points

• A character controlled by many genes is known as polygenic, or quantitative inheritance.
• Such characters demonstrate continuous variation.
• Examples of Quantitative characters are plant height, yield of crops (size, shape and number of seeds and fruits per plant), and intelligence in human beings and milk yield in animals have been found to be determined by many genes and their effects have been found to be cumulative.
• Each gene has a certain amount of effect.
• The more is the number of dominant genes, the greater will be the expression of the character.
• Quantitative inheritance is also multiple factor inheritance.

Additional Information

•  A character controlled by only a few genes is known as an Oligogenic or qualitative character
• Oligogenic characters demonstrate discontinuous variation i.e., traits are discrete.
• Blood type is an example of Quantitative character.

The correct answer is Sharbati Sonora.

Key Points

• Among the options, only Sharbati Sonora is an example of a variety of wheat.
• The process of the utilization of induced mutation in crop improvement is called mutation breeding.
• Sharbati Sonora is an example of mutation breeding.
• It is produced from Sonora-64 by using gamma rays.
• Sharbati Sonora was developed by the gamma irradiation of a Mexican variety (Sonora 64) with a mutant breed of wheat.
• Sharbati Sonora shows all the good characters of Sonora and in addition, an amber coloured grain instead of red-coloured one of Sonora 64 and more protein and lysine percentage in the grains.

Important Points 

• Wheat variety Sonora-64 was first developed by Norman E. Borlaug.
• Dr. M. S. Swaminathan is a pioneer mutation breeder. 
  • He has produced Sharbati Sonora
  • The formation of Sharbati Sonora was explained in a scientific paper published by Dr. M S Swaminathan.
• Sharbati Sonora was officially approved in 1967.
• Sharbati Sonora is responsible for the green revolution in India.

Additional Information 

• Oenothera Lamarckiana is a plant species that is important to the study of genetics.
  • It is popularly called "evening primrose" due to its habit of only showing its attractive flowers late in the day.
• Castor Aruna is a mutant variety of castor.
  • It was officially approved in 1969.
• Mirabilis jalapa is an ornamental species of Mirabilis plant.
  • It is popularly called the "four o'clock flower".