Viruses that utilize reverse transcriptase belong to the virus families Viruses that utilize reverse transcriptase belong to the virus families:. A. Retroviridae and Picornaviridae. B. Herpesviridae and Poxviridae. C. Rhabdoviridae and Herpesviridae. D. Hepadnaviridae and Retroviridae. E. Herpesviridae and Retroviridae.

D. Hepadnaviridae and Retroviridae.

Explanation:

Viruses are the infectious agents which possess the genetic material in the form of RNA or DNA.

The Virus which possess RNA as genetic material is known as the retroviruses as they perform reverse transcriptase activity and form DNA from RNA.

These retroviruses are classified into the group of viruses called the retroviridae and Hepadnaviridae based on the same genetic material and the method of replication mechanism.

Thus, Option-D is correct.

within 30 of the equator hope this

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.