The basis for the absolute refractory period is closure of the inactivation gates of the Na+ channel in response to depolarization. These inactivation gates are in the closed position until the cell is repolarized back to the resting membrane potential.

TLS Online TPP Program

#Id: 773

#Unit 3. Fundamental Processes

DNA polymerase does not synthesize new DNA strands de novo while RNA Polymerase initiates RNA synthesis de novo without primer

TLS Online TPP Program

#Id: 6609

#Unit 7. System Physiology – Animal

Progesterone promote secretory changes in the uterine endometrium, after ovulation

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#Id: 2993

#Unit 3. Fundamental Processes

The first DNA-synthesizing enzyme to be characterized was DNA polymerase I, which is a single polypeptide of 103 kD, The chain can be cleaved into two parts by proteolytic treatment.

The larger cleavage product (68 kD) is called the Klenow fragment. It is used in synthetic reactions in vitro, It contains the polymerase and the proofreading 3'-5'  exonuclease activities.

The small fragment (35 kD) possesses a 5 '-3' exonucleolytic activity, which excises small groups of nucleotides, up to - 10 bases at a time. This activity is coordinated with the synthetic/ proofreading activity. It provides DNA polymerase I with a unique ability to start replication in vitro at a nick in DNA.

TLS Online TPP Program

#Id: 6669

#Unit 3. Fundamental Processes

There are three type of Splicing signals 

 Major U2-type or GU-AG introns

Minor U12-type or AU-AC introns

Minor U12-type with GU-AG introns (hybrid type)

TLS Online TPP Program

#Id: 6874

#Unit 3. Fundamental Processes

Heterochromatin and RNAi are required to establish the human CenH3 homolog, CENP-A, at centromeres.