Answer:
Option A, Ohio River and the Missouri River
Explanation:
The historical evidences clearly indicate that Ohio River did not exist before the last ice advances. Before Ohio and Missouri river, the major glacier drainage of the east-west direction happens in Teays River. When ice of the glaciers blocked the Teaya river valley, then the Ohio was formed.
Like Ohio, Missouri river did also not exist before Pleistocene and during that time the largest drainage in North America take place in the Hudson's Bay
Hence, option A is correct
No, the sickle-cell anemia allele won't be eliminated by natural selection.
Sickle-cell anemia trait is controlled by a single gene and the allele (S) for sickle-cell anemia is a harmful autosomal recessive.
It is caused by a mutation in the normal allele (A) for hemoglobin (a protein on red blood cells).
Heterozygotes (AS) with the sickle-cell allele are resistant to malaria, a deadly tropical disease. It is common in many African populations.
In these areas, (S) carriers have been naturally selected, because their red blood cells, containing some abnormal hemoglobin, tend to be in sickle shape when they are infected by the malarial parasite.
Therefore, they are more likely to survive and reproduce. This keeps the S allele in the gene pool.
Learn more about Sickle-cell anemia on
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Answer:
The correct answer is allopatric speciation.
Explanation:
Allopatric speciation occurs when a geographical barrier comes between a species population living in the same area. This geographical barrier separates the population into two different geographical area which do not have the same condition.
So as both the separated population get different habitat environment to live so they evolve differently from each other. So natural selection and genetic drift works differently in both the population which brings genetic changes in the population and helps in creating a new species.
Answer:
Anticodon. The anticodon region of a transfer RNA is a sequence of three bases that are complementary to a codon in the messenger RNA. During translation , the bases of the anticodon form complementary base pairs witht the bases of the codon by forming the appropriate hydrogen bonds.
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