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E. coli cells with a mutated z gene of t...

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

A

In the presence of glucose, E.coil cells do not utilize lactose

B

They cannot transport lactose from the medium into the cell

C

The lac operon is constitutively active in these cells

D

They cannot synthesize functional a-galactosidase

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The correct Answer is:
B
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The wild type E. coli cells are growing in normal medium with glucose. They are transferred to a medium containing only lactose as sugar. Which of the following changes take place ?

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How would lac operon operate in E. coli growing in a culture medium where lactose is present as source of sugar ?

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Niels Bohr a Danish physicist received his PhD from the University of Copenhagen in 1911. He that spent a year with J.J. Thomson and Ernest Rutherford in England. In 1913, he returned to Copenhagen Where he remained for the rest of his life. In 1920 he was named Director of the Institute of theory! Physics After first World War Bohr worked energetically for peaceful uses of atomic energy recieved the first Atoms for Peace award in 1957 Bohr was awarded the Nobel Prize in Physics 1922 (a) The Angular momentum of an electron in a given stationary state can be expressed as m_e vr =h/(2pi) where n=1, 2,3 ...... Thus an electron can move only in those orbits for which its angular momentum is integral multiple of h/2 pi that is why only certain fixed orbits are alowed (b) The radii of the stationary states are expressed as r_n=n^2a_0 where a_0 =52.9 pm. Thus the radius the first stationary state, called the Bohr radius, is 52.9 pm. Normally the electron in the hydrogen atom is found in this orbit (that is n =1). As n increases the value of r will increase (c) The most important property associated with the electron E_n=-2.18xx10^(-18)(Z^2/n^2)J n=1,2,3 (d)it is also possible to calculate to calculate the velocities of electrons moving in these orbits by using v_n=2.18 10^6xxZ/n m/sec. Qualitatively the magnitude of velocity of electron increases with increase of positive charge on the nucleus and decreases with increases the value of n. (e)Bohr's theory can also be applied to th ions containing only one electron, similar to that present it hydrogen atom. For example , He^+ Li^(2+) , Be^(3+) and so on. given by the expression Ex=-218x n=1,2,3 (d) It is also possible to calculate the velocities of electrons moving in these orbits by using V 2.1810 cm/sec Qualitatively the magnitude of velocity of electron increases with increase of positive charge on the nucleus and decreases with increase the value of n (e) Bohr's theory can also be applied to the ions containing only one electron, similar to that presenti hydrogen atom For example, Help, Be and so on Choose the correct statement

AAKASH INSTITUTE ENGLISH-MOLECULAR BASIS OF INHERITANCE -ASSIGNMENT (SECTION -C) Previous Years Questions
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  2. During transcription, RNA polymerase holoenzyme binds to a gene promot...

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  3. E. coli cells with a mutated z gene of the lac operon cannot grow in m...

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  4. Nucleotides are building blocks of nucleic acids. Each nucleotide is a...

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  5. Which one of the following makes use of RNA as a template to synthesi...

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  6. Uridine, present only in RNA is

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  7. Which of the following is not a property of the genetic code ?

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  8. One of the most frequently used techniques in DNA fingerprinting i...

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  9. In an inducible operon, the genes are

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  10. A single strand of nucleic acid tagged with a radioactive molcule is c...

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  11. The reaction, Amino acid + ATP rarr Aminoacyl -MAP+ P-P depicts :

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  12. The transcription of any gene is the indication of its :

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  13. mRNA direct the building of proteins through a sequience of

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  14. Beadle and Tatum showed that each kind of mutant bread mould they stud...

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  15. Which one contains four pyrimidine bases?

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  16. The 1992 Noble Prize for medicine was awarded to Edmond H. Fischer ...

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  17. Initiation codon in eukaryotes

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  18. In E.coli, lac operon is induced by

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  19. Protein helping in opening of DNA double helix in front of replication...

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  20. In protein synthesis the polymerization of amino acids involves three ...

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