Crossing over occurs at the four-strand stage when two homologous chromosomes, each consisting of a pair of sister chromatids, are paired. Each crossover involves just two of the four strands and generates two recombinant strands.
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Answer:
Volcanic degassing of volatiles, including water vapour, occurred during the early stages of crustal formation and gave rise to the atmosphere. When the surface of Earth had cooled to below 100 °C (212 °F), the hot water vapour in the atmosphere would have condensed to form the early oceans.
Explanation:
The four major organic compunds are lipids, carbohydrates, proteins, and nucleic acids.
Lipids are used to store energy, insulate insulate, and they help build cell membranes. Examples of lipids are fats, oils, and waxes.
Carbohydrates are used to give us quick energy and they help build cell walls. Examples of carbohydrates include bread, pasta, cereal, and rice.
The role of proteins is to build our bodies, help our immune system, and help cells communicate. Such examples include meat, beans, eggs, fish, nuts, soy, and dairy.
Finally, Nucleic acids are used to store gentetic info. Anything plant or animal based is considered a nucleic acid.
Explanation:
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.
Nucleotides are composed of three subunit molecules: a nucleobase, a five-carbon sugar (ribose or deoxyribose), and a phosphate group consisting of one to three phosphates. The four nucleobases in DNA are guanine, adenine, cytosine and thymine; in RNA, uracil is used in place of thymine.
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Answer:
The eukaryotes, bacteria, and archaea that live in and on the human body are called normal microbiota. When they were originally discovered, scientists thought that the relationship between these organisms was parasitic because they thought that the organisms benefit from living on the host but did not help the host. In recent years, researchers have determined that most of our resident microbes derive and give benefit to the host. This makes the relationship between host and microbe one of mutualism. Pathogenic, on the other hand, are microbes that cause diseases.
