Because one of them dies and another one doesn’t
Solution:
The difference between them are:
The humoral system of immunity is also called the antibody-mediated system because of its use of specific immune-system structures called antibodies. The first stage in the humoral pathway of immunity is the ingestion (phagocytosis) of foreign matter by special blood cells called macrophages. The macrophages digest the infectious agent and then display some of its components on their surfaces. Cells called helper-T cells recognize this presentation, activate their immune response, and multiply rapidly. While,
The cell-mediated immune response involves cytotoxic T-cells, or killer-T cells. Body cells that have been infected by foreign matter often present components of that material on their surfaces. Killer-T cells recognize these displays and respond by ingesting or otherwise destroying the infected cell. Killer-T cells are also important in the body's defenses against parasites, fungi, protozoans, and other larger cells that might have found their way into the body. The killer-T cells recognize these large invaders by their foreign proteins and then destroy them.
This is the required answer.
Ionic bond is a compound made up of a meta and a non-metal eg NaCl (sodium chloride)
covalent bond is made up of two non-metals eg H2O (water)
Answer:
When homologous chromosomes form pairs during prophase I of meiosis I, crossing-over can occur. Crossing-over is the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome. It is obviously another source of genetic variation in offspring.
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The sequence of bases on the other half of the DNA molecule would be CTAATGT from left to right, because each cytosine base pairs with a corresponding guanine base, and each adenine base pairs with a corresponding thymine base.