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Elena L [17]
3 years ago
10

In the United States, the parasite that causes malaria is not present, but it is present in African-Americans whose ancestors we

re from equatorial Africa. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa?
Biology
1 answer:
slava [35]3 years ago
5 0

Answer: DIRECTIONAL SELECTION; STABILIZING SELECTION.

Explanation: In the United States of America the parasite that causes Malaria is not present,the parasite that causes Malaria are known to be a protozoa of the Plasmodium specie(Plasmodium: P. falciparum, P. malariae, P. ovale and P. vivax.).

DIRECTIONAL SELECTION is also known as positive selection where an advantageous allele increases as a consequence of differences in survival rate and reproduction among different phenotype Population.

STABILISING SELECTION is a type of natural selection in which a trait tend to remain stable,no one trait is felt more.

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Duchenne muscular dystrophy is an X-linked recessive disease. A phenotypically normal couple wants to start a family. The woman’
Andreyy89

Answer:

\frac{1}{8}

Explanation:

From the question: Duchenne muscular dystrophy is an X-linked recessive disease.

Now for an X-linked recessive disorder to be affected by a male individual; it only requires the presence of only one copy of the recessive allele of the disease to be present BUT in a female individual. both copies of the recessive allele must be present.

Let the X-linked recessive disease(i.e Duchenne muscular dystrophy) be = (ⁿ)

However, we are told that the couples are normal and are unaffected. Therefore;

the male partner (XY) will be:   X^NY

the female partner (XY) will be: X^NX^N

Similarly, the question proceeds by telling us that: the woman's brother has the disease.

Definitely, it's possible that this unaffected woman is a carrier of the disease.

So, if she is a carrier; we have her traits to be: X^NX^n

NOW, if a cross exist between these couples; we have

X^NY     ×        X^NX^n

                     X^N                         Y

X^N                X^NX^N                  X^NY

X^n                 X^NX^n                   X^nY

So, we have offspring as follows:

X^NX^N  = normal unaffected female  

X^NY     = normal unaffected male

X^NX^n   = female carrier for the Duchenne muscular dystrophy disease

X^nY      = affected male with the Duchenne muscular dystrophy disease

So, the probability of the child to be affected with the disease = \frac{1}{4}

Also, the probability that the first child will be a male or a female = \frac{1}{2}

∴

the  probability that the couple’s first child will be affected = \frac{1}{4}*\frac{1}{2}

=\frac{1}{8}

4 0
3 years ago
How can it be possible that scientists do not currently have fossil evidence for every organism that once lived?
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Answer:

How can you know what happened millions of years ago if no one was there to see it? Evidence and observation are the building blocks of all scientific inquiry; ... of the fossil record, geological formations, and genetics attest to change having taken ... clues together into a cohesive explanation of the diversity of living things. Because of the specialized and rare conditions required for a biological structure to fossilize, many important species or groups may never leave fossils at all. Even if they do leave fossils, humans may never find them—for example, if they are buried under hundreds of feet of ice in Antarctica.

Explanation:

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2 years ago
Which connective tissue disorder is characterized by insoluble collagen being formed and accumulating excessively in the tissues
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Answer; 
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Scleroderma is a connective tissue disorder that is characterized by insoluble collagen being formed and accumulating excessively in the tissues. 

Explanation; 
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Over a period of time, the beetles once again reached carrying capacity and sustained it for many years. However, pollution from
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Answer:

As the beetles have a uniform distribution, at a carrying capacity of 14,600 beetles, there are about 128 beetles per hectare. Because 55 hectares are now unlivable, the carrying capacity would decrease by about 7,040 individuals (55 × 128).

Therefore, the carrying capacity of the ecosystem will be (old carrying capacity – decrease in carrying capacity) = (14,600 – 7,040) = 7,560 beetles.

Explanation:

answer from Plato

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Explanation:

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