<h3><u>Answer and explanation;</u></h3>
- DNA is a double stranded molecule. Covalent and hydrogen bonds pray important roles in the functioning of DNA molecules.
- <em><u>Covalent bonds occur within each linear strand and strongly bond the nucleotide bases, sugars, and phosphate groups occurring both within each component and between components.</u></em>
- <em><u> Hydrogen bonds occur between the two strands and involve a base from one strand with a base from the second in complementary pairing.</u></em>
- Hydrogen bonds helps the complementary base pairs in DNA; guanine with cytosine and adenine with thymine to connect to one another. The hydrogen bonds between these complementary pairs helps keep the two strands of DNA helix together.
Answer:
CD4 on the surface of helper T-cells.
Explanation:
MHC class II ( major histocompatibility complex) molecules are processed from the exogenous source. The presentation of antigen on cells are important for the adaptive immune response.
MHC class II interact with CD 4 present on the surface of T helper cells. This interaction is important for the generation of an immune response. Helper T cells can release cytokines and can perform phagocytosis.
Thus, the correct answer is option (C).
This figure illustrates 3 hypotheses of how a cancer stem cell may arise: (1) A stem cell undergoes a mutation, (2) A progenitor cell undergoes two or more mutations, or (3) A fully differentiated cell undergoes several mutations that drive it back to a stem-like state.
Scientists collect ongoing data from many locations around the world. They then input this data into a mathematical or computer-based model to simulate real-world conditions.
<h3>What is climate forecasting?</h3>
Weather averages and other climatic characteristics are predicted by climate forecasts from a few weeks to a few years in advance. Such forecasts are increasingly being made using thorough models of the Earth's climate system.
Since it aids in forecasting future climate conditions, climatology and weather forecasting are crucial. The likelihood that snow and hail will reach the surface can be calculated using latitude. You may also determine the thermal energy from the sun that a location can get.
Learn more about climate forecasting, here:
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