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
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
Which one of the following hydrolysis internal phosphodiester bonds in a polynucleotide chain?
Lipase
Exonuclease
Endonuclease
Protease
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 - galactosidase
D.
they cannot synthesize functional - 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 - 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 - galactosidase.
(ii) Lac Y (800 bp)- This gene codes for enzyme galactose permease. It is a membrane bound protein and helps in the transport of metabolites.
(iii) Lac A (800bp)- This gene codes for enzyme - galactose transacetylase. It transfers an acetyl group from acetyl Co- A to - galactosidase.
DNA replication generally proceeds in a
5 3 direction
3 5 direction
3 3 direction
5 5 direction
DNA polymerase enzyme is required for synthesis of
DNA from RNA
RNA from DNA
DNA from DNA
RNA from RNA