Explanation:
Melanin is the pigment which absorbs UV light and it is present in skin and gives black colour to it.As we can see africans usually have black skin as they have to face direct uv light.
Answer:
The correct option is A. Steroid hormones exert their action by entering the nucleus of a cell and initiating or altering the expression of a gene.
Explanation:
Steroid hormones are derived from cholesterol and regulate multiple biological processes. All steroid hormones exert their action by crossing the plasma membrane and by binding with their respective intracellular receptors. They stimulate cell growth in a very different way, their lipophilic nature gives them the ability to cross lipid barriers, so, without the need for extracellular signals, these hormones can easily enter the cell, cross the cytoplasm and reach the nucleus. There they bind to specific receptors that are associated with DNA promoter regions, modifying their structure and promoting the expression of the genes under their control.
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The answer is 3 because plants absorb and use CO2, sunlight, and water to create glucose and expel leftover oxygen in the form O2.
9:1
What is coagulation test?
When you cut yourself, clotting stops the blood from becoming excessive. Your blood should not clot as it flows through your veins, though. These clots have the potential to develop and move through your bloodstream to your heart, lungs, or brain. A heart attack, stroke, or even death could result from this.
Coagulation assays assess the speed and consistency of blood clotting. Your doctor can use testing to determine your risk of excessive bleeding or the occurrence of clots (thrombosis) in one of your blood arteries.
Venous blood samples for coagulation assays should be drawn into a blue top tube containing 3.2% buffered sodium citrate to produce whole blood samples with a 9:1 blood to anticoagulant ratio.
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