89) During fasting, glucose is synthesized from gluconeogenesis. Where is glucos
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Question
89) During fasting, glucose is synthesized from gluconeogenesis. Where is glucose used?
During fasting glucose is directed to the brain.
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90) Why does DNA polymerase need a RNA primer for replication of chromosomes?
DNA polymerase cannot start synthesis, only extends on an existing polynucleotide. RNA polymerase can synthesize without an existing primer.
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91) During replication of chromosomes, synthesis of one strand is continuously extending. Another strand extend discontinuously. Why?
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92) Histone proteins are core of nucleosomes. DNA wraps around them. Both DNA and histones are involved in regulation of gene expression. Transcription factors and enhancers are other elements of regulation. What would be like if a gene has a promoter but does not have tissue specific regulatory protein binding sites?
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93) Some of cancer causing genes are involved in DNA repair such BRCA1 and BRCA2. Why do defects in DNA repair increase chance of getting cancer?
Explanation / Answer
During fasting, glucose is synthesized from gluconeogenesis. Gluconeogenesis is a process of synthesis of glucose from non-carbohydrate sources such as lactate, pyruvate, glycerol and glucogenic amino acids. Gluconeogenesis is one of the important metabolic processes of the body, through which blood glucose levels are maintained.
During fasting gluconeogenesis occurs because some of the cells like brain cells (they can generate 20% of energy from ketone bodies), testes, erythrocytes (lack og mitochondria), kidney, lens, and cornea are dependant upon glucose as their sole energy source, they cannot synthesise energy from non-glucose sources. Thus glucose mainly directed towards all these cells, but mailny to brain cells (due to its large mass).
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