Cry-I endotoxins obtained from Bacillus thringiensis are effective against 

  • mosquitoes

  • flies

  • nematodes

  • nematodes


B.

flies

Insect-resistant transgenic plants contain either a gene from the bacterium Bacillus thuringiensis or some other gene. The cry gene of bacillus thuringiensis produces a protein which forms crystalline inclusion in the bacterial strains. Cry-I endotoxins are effective gains Lepidoptera (eg flies). Cry- V and Cry-VI proteins are effective against are ingested by insects, they are dissolved in the alkaline juices present in the midgut lumen. The gut proteases process them hydrolytically to release the core toxic fragments. The toxic fragments are believed to bind to specific high-affinity receptors present in the brush border of midgut epithelial cells and causing their swelling and eventual lysis.

436 Views

What is antissense technology? 

  • A cell displaying a foreign antigen used for synthesis of antigens

  • Production of somaclonal variants in tissue cultures. 

  • When a piece of RNA that is complementary to sequence is used to stop expression of a specific gene.

  • When a piece of RNA that is complementary to sequence is used to stop expression of a specific gene.


C.

When a piece of RNA that is complementary to sequence is used to stop expression of a specific gene.

The antisense RNA technology simply involves the synthesis of RNA molecules that are complementary to the mRNA molecules produced by transcription of a given gene.  Usually t his antisense RNA will not contain the regulatory sequences required for translation but even if does it will not usually specify a functional product. Instead, most antisense RNAs contain multiple termination codons in all three reading frames. However, when antisense RNA molecules are present in the same cytosol with sense (mRNA) molecules of a gene, the antisense RNA and mRNA molecules will anneal to form duplex RNA molecules. These duplex RNA molecules cannot be translated thus, the presence of antisense RNA will block translation of the mRNA of the affected gene.

254 Views

In the DNA molecule

  • the  total amount of purine nucleotides and pyrimidine nucleotides is not always equal

  • there are two strands, which run parallel in the 5' →3' direction

  • the proportion of adenine in relation to thymine varies with organism

  • the proportion of adenine in relation to thymine varies with organism


D.

the proportion of adenine in relation to thymine varies with organism

In DNA molecule the adjacent deoxyribonucleotides are joined in a chain by phosphodiester bridges or bonds, which link the 5' carbon of deoxyribose of one mononucleotide unit with 3' carbon of deoxyribose of next mononucleotide unit, According to Waston and Crick DNA molecule consists of two such polynucleotide chains wrapped helically around each other, with the sugar-phosphate chain on the outside and purine and pyrimidine on the inside of helix. Two strands run antiparallel, ie, one strand have phosphodiester linkage in 3'→5' direction while another strand has phosphodiester linkage in 5' →3' direction.

Chargaff (1950) suggested that despite wide compositional variations exhibited by different types of DNA the total amount of purines equalled the total amount of purines equaled the total amount of pyrimidines (A + G = T + C)

233 Views

Advertisement

Polymase is formed by

  • several ribosomes attached to a single mRNA

  • many ribosomes attached to a strand of endoplasmic reticulum

  • a ribosome with several subunits

  • a ribosome with several subunits


A.

several ribosomes attached to a single mRNA

In prokaryotes, ribosomes attach to the 5 end of mRNA as soon as transcription begins. A bunch of ribosome moves along a single m RNA molecules adding 15 amino acids second to the polypeptide chain, almost the same speed at which RNA polymerase transcribes the mRNA. The group of ribosomes together with single mRNA molecules, they are translating is called polysome. The use of polysomes si advantageous to a cell since the overall rate of protein synthesis is increased compared to the rate that would occur if there were no polysomes.

In eukaryotic cells, the ribosomes are attached to rough endoplasmic reticulum by ribophorin protein.Electron microscopy reveals that membranes of homogenised reveal that membranes of homogenised endoplasmic reticulum disrupt to form closed vesicles called microsomes.

264 Views

Advertisement

Which one of the following pairs of nitrogenous bases of nucleic acids, is wrongly matched with the category mentioned against it?

  • Thymine, Uracil - Pyrimidines

  • Uracil, Cytosine - Pyrimidines

  • Guanine, Adenine - Purines

  • Guanine, Adenine - Purines


D.

Guanine, Adenine - Purines

DNA and RNA the principal genetic materials of living organisms are chemically called nucleic acids. These are polymers of nucleotides. Each nucleotide is composed of phosphoric acid, a Pentose sugar and a nitrogenous base. The nitrogenous bases are of two types, ie, Purine and pyrimidines.

Prices are heterocyclic and two rings compound, eg, adenine, guanine.
Pyrimidines are single ring compound, eg, thymine, cytosine, uracil.

274 Views

Advertisement