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Luda [366]
3 years ago
13

A) How does HIV bind to a host cell?

Biology
1 answer:
Taya2010 [7]3 years ago
7 0

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.

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Why does a female’s cervix dilate prior to delivering a baby?
cluponka [151]

Effacement: The cervix – which is normally long and thick, measuring about 1-2 inches, starts to get shorter and thinner. This process is known as effacement. As the cervix gets more and more effaced, it gets shorter and shorter and “pulled up” into the lower part of the uterus.

Dilation: At the same time, the cervix softens and begins to open up – known as dilation. This widening, allows a smooth passage for the baby’s head and the rest of the body from the uterus into the vaginal canal.

5 0
3 years ago
Human ABO blood type is controlled by the I locus and has three possible alleles. The alleles which code for type A blood (IA) a
Oxana [17]

Answer:

1/8 (12.5 %)

Explanation:

Cross: IAi X  IAIB

F1: 1/4 IAIA 1/4 IAIB 1/4 IAi 1/4 IBi

Phenotypes:

- IAIA and IAi >> type A blood

- IBi >> type B blood

- IAIB >> type AB blood

Phenotypic frequency type A blood: 1/2  (i.e., 1/4 IAIA +  1/4 IAi) >>

Probability to have 3 offspring with type A blood: 1/2 x 1/2 x 1/2 = 1/8

The human ABO blood group is a system consisting of there different alleles: A, B, and O. This system is used in genetics as an example of codominance because both A and B alleles are expressed in heterozygous individuals (i.e., IAIB), whereas only the allele A is expressed in individuals that have A and O alleles (since O allele is recessive to the A and B alleles).

6 0
3 years ago
In which kingdom are an overwhelming majority of its individuals producers?
Liono4ka [1.6K]

The plantae kingdom has an overwhelming majority of the producers, this may not be true. The producers are mostly present as autotrophs that make food using the sunlight. Other kingdoms like the bacteria have varied forms of producer, both the autotrophs like the cyanobacteria and the chemotrophs like halothiobacillus that use the internal heat of the Earth at the bottom of the dark ocean floor to synthesise their food.

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3 years ago
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Answer:

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Explanation:

7 0
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A species that influences the survival of many other species in an ecosystem is called a(n)
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Keystone species, they kinda hold the food webs together
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3 years ago
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