E. coli cells with a mutated Z gene of the lac operon cannot grow

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 Multiple Choice QuestionsMultiple Choice Questions

131.

RNA is not found in

  • chromosome

  • plasmalemma

  • nucleolus

  • ribosome


132.

Sequence of DNA (non-coding) is known as

  • exon

  • intron

  • cistron 

  • none of these


133.

Which one of the following makes use of RNA as a template to synthesize DNA?

  • Reverse transcriptase

  • DNA dependant RNA polymerase

  • DNA polymerase

  • RNA polymerase


134.

During transcription holoenzyme RNA polymerase binds to a DNA sequence and the DNA assumes a saddle like structure at that point. What is that sequence called?

  • CAAT box

  • GGTT box

  • AAAT box

  • TATA box


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135.

Which one of the following hydrolysis internal phosphodiester bonds in a polynucleotide chain?

  • Lipase

  • Exonuclease

  • Endonuclease

  • Protease


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136.

E. coli cells with a mutated Z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because

  • in the presence of glucose, E. coli cells do not utilize lactose

  • they cannot transport lactose from the medium into the cell

  • the lac operon is constitutevely active in these cells

  • they cannot synthesize functional β- galactosidase


D.

they cannot synthesize functional β- galactosidase

Lac operon is a cluster of genes encoding three proteins that bacteria use to obtain energy from the sugar lactose. There are three structural genes in lac operon.

(i) Lac Z (3063bp)- This genes codes for enzyme β- galactosidase. It breaks lactose into glucose and galactose. Therefore, E. coili cells with a mutated Z genes cannot grow in medium containing only lactose as the source of energy because they cannot synthesize functional β- galactosidase.

(ii) Lac Y (800 bp)- This gene codes for enzyme β galactose permease. It is a membrane bound protein and helps in the transport of metabolites.

(iii) Lac A (800bp)- This gene codes for enzyme β- galactose transacetylase. It transfers an acetyl group from acetyl Co- A to β- galactosidase.


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137.

What's the difference between RNA and DNA?

  • Base

  • Sugar

  • Sugar and base

  • Phosphate


138.

In split genes the coding sequences are called

  • introns

  • exons

  • cistrons

  • operons


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139.

DNA replication generally proceeds in a 

  • 3 direction

  • 5 direction

  • 3 direction

  • 5 direction


140.

DNA polymerase enzyme is required for synthesis of

  • DNA from RNA

  • RNA from DNA

  • DNA from DNA

  • RNA from RNA


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