D)crossing over of homologous chromosomes during meiosis.
Answer:
When helicase mutations occur, problems in DNA replication are found. The helicases are proteins that open the 2 strands of DNA to initiate the duplication, they are responsible for breaking the hydrogen bonds between the two DNA chains, thus separating the chains, also they have the function of repairing DNA mutations, if there is mutation in the gene that encodes them, various functions will be absent in the cell.
Explanation:
Fossil fuels are important energy sources for our every day activities.
Formation of fossil fuels
Fossil fuels forms from the accumulation and burial of organisms in a basin of deposition. Instead of the organisms decaying, they preserve their carbon content. To be worthy of becoming fossil fuels, organisms must be buried in an environment where there is little to no oxygen to fast-track decomposition of the buried organic matter. Increase in temperature and pressure causes the organic matter to transform into fossil fuels.
How are they obtained
First, different fossil fuels have their extraction techniques because they occur in different physical state of matter.
For the solids e.g coal: exploration is carried out first and if a prospect is delineated, mining engineers design the best way to extract the coal from nature. Coal is usually found laid in sedimentary beds in nature. Top layers of sediments can be removed to extract the coal.
For fluids such as crude oil and natural gas, after a prospect is identified, a rig is usually constructed to extract the fluid and gas. The natural pressure allows for the fluids the rise within the drill used in extraction.
How are they used
Coal and gas are used to power electrical generating plants. They are used to heat steams which drives turbines and produce electricity.
Natural gas is used as a domestic fuel for cooking and so also coal.
When crude is processed a lot of product is obtained. Gasoline is used to power most internal combustion engines. Some chemicals useful for manufacturing plastics, drugs e.t.c are also derived from the processed crude.
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D.)The enzyme changes shape and no longer fits the substrate.
High temp causes enzymes to speed up the reaction but too much heat and the enzyme might denature, losing its shape.
