Answer:
Oils repel water, so it helps these animals keep their fur dry, which helps them stay warm.
Answer:
False
Explanation:
The histones that are more positively charged, tight hardly to negatively charged DNA. So, enzymes, such as acetyltransferases, that reduce the positive charge of histones promote transcription.
Chromatin structure and its modifications can change the package of the DNA and consequently, alter the gene expression. The most common modifications of the chromatin are covalent modifications such as acetylation/deacetylation (by acetyltransferases and eacetylases), methylation (by methyltransferases), and phosphorylation (by kinases). This is the way of gene expression regulation.
The effects of modifications are different, for example methylation promotes condensation of the chromatin and as a consequence, prevents binding of transcription factors to the DNA (transcription is repressed).
Acetylation loosens the association between nucleosomes and DNA (because it neutralizes the positive charge of histones) and consequently promotes transcription. Deacetylation is a process opposite to acetylation.
Mitosis is the process of cell division, where one parent cell divides to produce two genetically identical daughter cells. This process is vital in growth and tissue repair.
The reason that tissue from the fetal stage is helpful in studying mitosis is because mitosis is continuously and rapidly occurring in this phase of life in humans. The high rate of mitosis is due to the need for the fetus to grow rapidly and develop the necessary parts for it to be born.
Answer: [D]: "oceans" .
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Note: Among the answer choices given—{aquifers, glaciers, lakes, oceans}—oceans are the saltiest (VERY salty—requiring "desalination" in order to obtain potable water.
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