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asambeis [7]
2 years ago
7

Can a person be exposed to hiv by hugging or shaking hands with an infected person? a. yes, because the virus can be transmitted

through sweat b. no, because none of the bodily fluids that carry the virus are on the surface of the skin c. no, not if the skin is completely covered d. yes, so you can't ever be too safe please select the best answer from the choices provided. a b c d
Biology
1 answer:
g100num [7]2 years ago
4 0

Answer: b

Explanation: b best fits how the transmission of hiv works

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A DNA fragment is introduced into the lacZ gene of a plasmid, which also contains an ampicillin resistance gene. What is the app
zhenek [66]

Answer: The bacteria transformed with this particular plasmid will form white colonies on the plates containing ampicillin and Xgal.

Explanation: The lacZ gene produces an enzyme called β-galactosidase which is responsible for the breakdown of lactose into glucose and galactose. The lacZ gene is one of the three genes (the other two being lacA and lacY) of the lac operon which is responsible for the transport and mechanism of lactose in E. coli and many other bacteria.

In recombinant DNA technology, when a plasmid is to be used to transform a host cell, such markers are used to help screen the transformed cells from the ones that have not taken up the plasmid. Xgal present in the plates is an artificial substrate which is hydrolyzed by

β-galactosidase into 5-bromo-4-chloro-indoxyl which will dimerize and oxidise into 5,5'-dibromo-4,4'dichloro-indigo. This is a blue pigment which will give blue color to the bacterial cells. Introducing a DNA fragment in this lacZ gene will make it non-functional so it will not be able to produce the enzyme.

Therefore, when a bacterial cell is transformed with a plasmid containing ampicillin resistance gene and a DNA fragment introduced in the lacZ gene and then grown on plates containing ampicillin and Xgal, white colored colonies will appear. The white colonies will show the bacterial cells that have successfully taken up the plasmid with the DNA fragment incorporated in the lacZ gene as this will render the gene non-functional and will not produce β-galactosidase which will breakdown Xgal to give blue colonies. Since the plates contain ampicillin, only the bacterial cells that have been successfully transformed with the plasmid ( the ones that have the DNA fragment and the ones without it) will grow as the ampicillin resistance will give them resistance against ampicillin in the plates. The bacterial cells that have not taken up the plasmid will not be resistant to ampicillin and will not form colonies on the plate.

This is called blue-white screening which is used to identify successfully transformed host cells. A picture of this is given in the attachment, taken from the following website:

https://www.mun.ca/biology/scarr/Blue_&_White_Colonies.html

8 0
3 years ago
Which of the following is NOT true of bacteria?
enyata [817]

If you go on mc3.edu/admissions/applying-to-mccc/testing-and-assessment/assets/biology-placement-test.pdf page 11 it will tell you all the answers to your questions....

Download pdf
5 0
3 years ago
true or false? to make a person breathe in, the volume of the chest cavity must decrease, creating a higher pressure in the thor
faltersainse [42]

The thorax is a very vital and important organ in the human body.

  • It is a structure that serves as a<u> </u><u>protective covering</u> for organs in the body such as<u> the lungs, the heart, some vital blood vessels</u> e.t.c

It is<u> false</u> that to <em>make a person breathe in, the volume of the chest cavity must decrease, creating a higher pressure in the thorax.</em>

  • When a person breathes in,  <u>the chest cavity expands (the volume increases) and the pressure in the thorax decreases.</u>

  • When a person breathes out, <u>the chest cavity decreases in size, and the pressure in the thorax increases. </u>

  • Therefore, we can see that the <u>process of breathing in humans</u>, follows the <u>principle of Boyle's Law.</u>

  • Boyle's law states that as the<u> volume increases there is a decrease in pressure</u> and <u>as the volume decrease there is an increase in pressure. </u>

Therefore, It is <u>false</u> that to <em>make a person breathe in, the volume of the chest cavity must decrease, creating a higher pressure in the thorax.</em>

To learn more, visit the link below:

brainly.com/question/24359876

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2 years ago
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erastovalidia [21]

Answer:

Explanation:more details please

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3 years ago
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Mandarinka [93]

Answer:

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