The lac operon consists of 

  • four regulatory genes only

  • one regulatory gene and three structural genes

  • two regulatory genes and two structural genes

  • two regulatory genes and two structural genes


B.

one regulatory gene and three structural genes

Lac operon is the operon that regulates lactose metabolism in the bacterium Escherichia coli. Its form wast first postulated in 1961 by Francois Jacob and Jacques Monod to explain the control of β- galactosidase synthesis and for this work, they were awarded Nobel Prize. Lac operon system or inducible operon system consists of regulator gene (i) promoter gene (z, y and a), repressor protein and inducer.
Drosophila

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Sickle cell anaemia is

  • an autosomal-linked dominant trait

  • caused by substitution of valine by glutamic acid in the β-globin chain of haemoglobin

  • caused by a change in a base pair of DNA

  • caused by a change in a base pair of DNA


C.

caused by a change in a base pair of DNA

Sickle-cell anaemia is caused by a change in a single base DNA. It is genetic disease reported from negroes. The individuals of stickle-cell anaemia are immune to malaria.

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In eukaryotic cell transcription, RNA splicing and RNA capping take place inside the

  • ribosomes

  • nucleus

  • dictyosomes

  • dictyosomes


A.

ribosomes

Transcripiton involves the transfer of genetic information from DNA to functional mRNA. In eukaryotes, the modification of newly formed primary mRNA transcripts (pre- m-RNA) to produce functional mRNA is called RNA processing or post-transcriptional modification. it occurs in the nucleus and involves gene-splicing (i.e removal of introns from primary transcript and splicing together of exons) and capping involves the formation of a cap at 5' end by condensation of guanylate residues. The fully processes mRNA molecules are exported from the nucleus to the ribosomes for translation in the cytoplasm.

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Which one of the following is now being commercially produced by biotechnological procedures?

  • Nicotine

  • Morphine

  • Quinine

  • Quinine


D.

Quinine

Nowadays, genetically engineered insulin is being produced at commercial level. the biotechnological procedure involves the synthesis of two DNA sequences corresponding to A and B insulin chains. The two DNA sequences or genes are made to fuse with plasmids and later allowed to form insulin chains.

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There is no DNA in 

  • an enucleated ovum

  • mature RBCs

  • a mature spermatozoan

  • a mature spermatozoan


A.

an enucleated ovum

The chromatin material inside the nucleus is composed of DNA, some proteins and RNA. In fact it is DNA- protein complex basically. Thus, in an enucleated ovum, DNA will be absent.

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