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3 years ago

Discovery of penicillin.

1 answer:

8 0

But it was not until 1928 that penicillin, the first true antibiotic, was discovered by Alexander Fleming, Professor of Bacteriology at St. Mary's Hospital in London.

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Explain the steps that you would use to focus on a specimen under a compound light microscope.

Rashid [163]

To start, move the objective lens to its lowest power setting. Place a slide on the stage with the label side up and the cover slip in the middle. You can only use the coarse focus knob when the power is low. If you can't see anything, move the slide a little while you look and focus. If nothing shows up, turn down the light and move the slide a little while you're looking and focusing. Once you're in focus on low power, move the slide to make the object of interest in the middle of it. Turn the objective to medium power and only change the fine focus. If you need to, turn the objective to high power and only adjust the fine focus.

8 0

2 years ago

HELP!! DNA was isolated from water samples taken from six different sites. This gel

VladimirAG [237]

After running DNA in a gel, bands of different sizes and species might appear. Scientists know silver carp are at North Shore site 1 because one of the bands in lane 1 matches a band in the positive control (Option C).

When DNA was isolated and run in a gel, many bands migrated to different points.

These bands were the different-sized fragments of DNA samples from different species from the six sites.

Researchers wanted to figure out where the silver carp is.

To do it, they needed to identify the bands on the gel that belonged to the silver carp DNA, so they included negative and positive controls to make comparisons.

<h3>Positive and negative Controls</h3>

Negative and positive controls guarantee the interpretations of the results.

The positive control shows the band sizes that belong to the silver carp DNA.

Any band in the sampling sites that matches one of the positive control bands indicates that the species is present at that site.

The negative control is the opposite. It is the absence of the species' DNA.

<h3>Results interpretation</h3>

As we can see, there are four sites where the bands match one of the bands of the positive control. These are,

North shore site 1
Chicago site 1
Calumet site 1
Calumet site 2

This means that at these four sites, the silver carp is present.

So scientists know silver carp are at North Shore site 1 because one of the bands in lane 1 matches a band in the positive control (Option C).

By looking at the lane of the North Shore site 1, we can also see another band (Thinner and grey). But this band does not match either of the positive control bands. This result suggests that the grey band belongs to another species' DNA.

You can learn more about gel electrophoresis at

brainly.com/question/9437877

brainly.com/question/895793

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3 years ago

Call me a pickle The Dramatics

marshall27 [118]

Answer:

u r a pickle the dramatics

3 0

3 years ago

Read 2 more answers

How to explain natural selection?

loris [4]

Natural selection is basically when organisms with the best traits survive and pass on their good traits to their offspring so that they will adapt easily and survive. Organisms who do not have ‘good traits’ that help them adapt and escape predators will be killed or eaten before they reproduce.
So in the end, natural selection is a form of evolution that allows the ‘fittest’ animals to survive and reproduce, while weeding out the unfit.

8 0

4 years ago

Name the trophic levels in an ecosystem and explain how energy moves through the trophic levels. Use the food chain and food web

ella [17]

Answer:

there are four trophic levels first are producers then primary consumers then secondary consumers then teritary consumers

Explanation:

grass - grasshopper - frog - snake - eagle is a simple food chain

4 0

2 years ago

Read 2 more answers

Discovery of penicillin.​

Discovery of penicillin.