Genetics And Plant Breeding - Study Mode

[#456] A virus free clone from a virus infected plant can be obtained by
Correct Answer

(D) Meristem culture

Explanation

Solution: A virus-free clone from a virus infected plant can be obtained by Meristem culture. Meristem culture is a plant tissue culture technique in which a plant's fastest growing tissue is cultured, and it is very helpful to produce virus-free plants, as the rate of meristem growth is always higher than virus cell to cell transmission.

[#457] Term heterosis was introduced by
Correct Answer

(B) Shull (1914)

Explanation

Solution: Term heterosis was introduced by Shull (1914). Heterosis, hybrid vigour, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. In proposing the term heterosis to replace the older term heterozygosis, G. H. Shull aimed to avoid limiting the term to the effects that can be explained by heterozygosity in Mendelian inheritance.

[#458] If a dihybrid is test crossed, the phenotype ratio of progeny will be
Correct Answer

(C) 1 : 1 : 1 : 1

Explanation

Solution: If a dihybrid is a test crossed, the phenotype ratio of progeny will be 1: 1 : 1 : 1. Dihybrid test crossing is an experimental cross in which we took one parent from the F1 generation with a heterozygous condition of two traits and another parent in double homozygous condition which will produce different types of gametes which will further fertilise to form new individuals.

[#459] The chemical mutagens usually induce
Correct Answer

(C) Gene mutation

Explanation

Solution: The chemical mutagens usually induce Gene mutation. Chemical mutagens work mostly by inducing point mutations. Point mutations occur when a single base pair of a gene is changed. These changes are classified as transitions or transversions. Mutations can occur through alterations of single bases in the DNA, or by loss or rearrangement of large sections of DNA.

[#460] Match the following columns: Column I Column II a. Polytene chromosome 1. With numerous chromosome b. Lampbrush chromosome 2. Oocytes c. Aerocentric chromosome 3. Centromere near one end d. Sat chromosome 4. With a satelite
Correct Answer

(B) a-1, b-2, c-3, d-4

Explanation

Solution: a. Polytene chromosome with numerous chromosomes - Polytene chromosomes are large chromosomes that have thousands of DNA strands. They provide a high level of function in certain tissues such as the salivary glands of insects. b. Lampbrush chromosome is oocytes - Lampbrush chromosomes (LBCs) are transcriptionally active chromosomes found in the germinal vesicle (GV) of large oocytes of many vertebrate and invertebrate animals. c. Aerocentric chromosome is centromere near one end - Acrocentric chromosomes are defined as having the centromere near and at the end of the chromosome. d. Sat chromosome is with a satellite - The satellite at metaphase appears to be attached to the chromosomes by a thread of chromatin. In addition to the centromere, one or more secondary constrictions can be observed in some chromosomes at metaphase. These chromosomes are called satellite chromosomes.