Explanation:
Proglottids are segments in cestodes that contain bot the male and female reproductive organs. These segments go ahead to make eggs and then dettach form the worm. They are excreted and become agents of infection on the next hoist. Proglittids formed near the neck of the worm are immature while those at the tail end are literally bags of mature eggs.
The scolex is the head of the worm that is attached to the host. It is also the part that ‘sucks’ nutrients from the host. It has hooks that it uses to anchor itself in the host. In some species, rather than hooks, there are suction-cups that use suction for anchorage.
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Incomplete dominance means that an allele is neither dominant nor recessive. An example would be the alleles for the genes that decide the color trait of a Mirabilis plant. 1. B. We should take a red petunia plant and a white petunia plant and have them crossbreed.
1. The correct answer is: The viral envelope proteins interact with CD4 and a co-receptor on the cell membrane.
Binding and entering the host cell are the first steps of the HIV virus infection. So, these steps play a major role in determining the ability of HIV to degrade the human immune system. Binding of HIV to CD4+ T lymphocytes (express chemokine receptors CCR5 and CXCR4 called co-receptors) triggers the fusion of the viral and host cell membranes, initiating infection (viral core gets into the cytoplasm).
Attachment of the virion can be:
• Nonspecific-envelop protein of the virus (Env) binds to cell-surface heparan sulfate proteoglycans
• Specific-Env binds to integrin.
2. The correct answer is: Activation of the host cell by cytokines, growth factors, or antigens.
After the viral capsid enters the cell, single-stranded RNA genome is released from the attached viral proteins and copied it into a complementary DNA (cDNA) molecule thanks to an enzyme called reverse transcriptase. Next step is the integration of the viral DNA into the host cell's genome. This process is done by another viral enzyme called integrase. The integrated DNA is transcribed into RNA and then translated into proteins that will help the package of new viruse particles.
3. The answer is: false
Reverse transcriptase is an enzyme that catalyzes the formation of DNA from an RNA template. Since the genome of the virus (HIV) is single stranded RNA, reverse transcriptase copies it into a complementary DNA (cDNA) molecule. Thanks to this enzyme, formed cDNA can be integrated into host’s genome. Because of this proprety, antiretroviral drugs used to treat HIV infection work as reverse-transcriptase inhibitors.
