( C ) -That the spontaneous generation doesn’t happen
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.
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Answer:
The answer is b. Both of them are characterized by selective permeability.
Explanation:
- Option a. states that both, the nuclear and the cell membrane have two layers. This is only true for the nuclear membrane that consists of two lipid bilayers whereas the plasma membrane only contains one layer.
- c. Only the nuclear membrane has nuclear pores that connect the two bilayers. The pores act as protein channels or passages that allow transport of materials. The cell membrane does contain channel proteins or transmembrane proteins but not protein channels.
- d. The nuclear membrane separates nuclear contents from the cytoplasm whereas the cell membrane separates cellular contents from the extracellular environment.
The answer is C.
A virus is made up of or consists of a nucleic acid in varying quantity which may either be RNA or DNA.
The nucleic acid is surrounded by a protein shell called a capsid. The word capsid comes from the Latin word capsa which means box.The capsid and the nucleic acid within it are together referred to as nucleoprotein.The capsid is made up of small sub units called capsomeres.
In many viruses, the nucleoprotein makes up the whole virus. More complex viruses have one or more further enclosing structures also made mostly of protein. These structures are referred to as envelopes and each envelop is specific to a particular virus.
I believe there has to be enough activation energy for a reaction to occur in the first place, if that is what you are referencing
