Definition: "Copying of information from DNA to RNA which exit nucleus is known as transcription"
Explanation: Transcription is a vital process for living organisms, because it is a staring point for protein synthesis. It occurs inside the nucleus and is carried out by RNA polymerase enzyme. In eukaryotes RNA pol is of three types: these are RNA Pol 1, RNA Pol 2, and RNA Pol 3. In prokaryotes it is of only one type.
Steps in transcription: Transcription consists of three main steps
1. Initiation: In this step RNA pol attach to DNA template at 5 prime end in the promoter region to start the formation of complementary strand of RNA. In prokaryotes there is a region called
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Pribnow box, with the </span>consensus sequence<span> TATAAT present about 10 base pair away from site that serves as a transcription initiation. In eukaryotes the promoter region is more complex it contain activator and enhancer.
2. Strand elongation: </span><span>Once transcription is initiated, the DNA double helix unwinds and RNA polymerase reads the template strand, adding nucleotides to the 3′ end of the growing chain.
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3. Transcription Termination:
Terminator sequences are found close to the ends of non-coding sequences. Before termination polyadenylation occurs. <span>
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The endocrine system is composed of the following:
1) hypothalamus
2) pituitary gland
3) thyroid and parathyroids
4) adrenal glands
5) pineal gland and gonads
6) pancreas
Pituitary gland is involved in gigantism. Pituitary gland produces the growth hormone. Excessive growth hormone released by the pituitary may result to gigantism.
The enlargement of the thyroid gland is called goiter. It is a symptom of hypherthyroidism, a condition wherein levels of thyroid hormones in the blood are highly excessive.
1. The lining up of chromosomes by the spindle fibers takes place at metaphase II phase. It is the second stage of meiosis II, the spindle draws the chromosomes towards the metaphase plate.
2. The formation of the nuclear envelope around each set of DNA takes place in telophase II. Along with the formation of the nuclear envelope, the process of cytokinesis also takes place in telophase II, producing four daughter cells, each comprising a haploid set of chromosomes.
3. The sister chromatids are pulled apart in anaphase II stage. In this phase, the sister chromatids are migrated towards the opposite poles of the cell with the help of protein fibers.
4. The centromeres are moved towards the poles of the cell at prophase II stage.
temperature regulation, heat absorption, and nutrition transportation