Answer:
The delivery of the paternal genome to the egg is a primary goal of fertilization. In preparation for this step, the nucleus of the developing spermatozoon undergoes extensive morphological and biochemical transformations during spermatogenesis to yield a tightly compacted sperm nucleus. These modifications are essentially reversed during fertilization. As a result, the incorporated sperm nucleus undergoes many steps in the egg cytoplasm as it develops into a male pronucleus. The sperm nucleus (1) loses its nuclear envelope, (2) undergoes nucleoprotein remodeling, (3) decondenses and increases in size, (4) becomes more spherical, (5) acquires a new nuclear envelope, and (6) becomes functionally competent to synthesize DNA and RNA. These changes are coordinate with meiotic processing of the maternal chromatin, and often result in behaviors asynchronous with the maternal chromatin. For example, in eggs fertilized during meiosis, the sperm nucleus decondenses while the maternal chromatin remains condensed. A model is presented that suggests some reasons why this puzzling behavior exists. Defects in any of the processes attending male pronuclear development often result in infertility. New assisted reproductive technologies have been developed that ensure delivery of the sperm nucleus to the egg cytoplasm so that a healthy embryo is produced. An emerging challenge is to further characterize the molecular mechanisms that control sperm nuclear transformations and link these to causes of human infertility. Further understanding of this basic process promises to revolutionize our understanding of the mystery of the beginning of new life.
Explanation:
The delivery of the paternal genome to the egg is a primary goal of fertilization. In preparation for this step, the nucleus of the developing spermatozoon undergoes extensive morphological and biochemical transformations during spermatogenesis to yield a tightly compacted sperm nucleus. These modifications are essentially reversed during fertilization. As a result, the incorporated sperm nucleus undergoes many steps in the egg cytoplasm as it develops into a male pronucleus.
Answer:
Gap 2 (G2): During the gap between DNA synthesis and mitosis, the cell will continue to grow and produce new proteins. At the end of this gap is another control checkpoint (G2 Checkpoint) to determine if the cell can now proceed to enter M (mitosis) and divide.
Explanation:
Cellular organization, Method of reproduction, Metabolism, Heredity, response to stimuli, homeostasis, adaptation to evolution, and growth and development,
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Answer:
the answer is D :)
Explanation:
Active transport uses energy molecules to move particles like sodium, against their concentration gradients, from areas of low concentration to areas of high concentration.
Yes! a region of the body with greater sensory acuity to have cutaneous receptors with large receptive fields, or small receptive fields.
The sensory receptor located in the skin is known as a cutaneous receptor ( the dermis or epidermis). The somatosensory system includes them. Mechanoreceptors (pressure or distortion), nociceptors (pain), and thermoreceptors are cutaneous receptors (temperature). The lowest spatial resolution is found in the thigh and calf area, whereas the fingertips have the highest spatial resolution (and the smallest receptive fields) (and largest receptive fields). Two-point discrimination threshold measurements can be used to assess the spatial resolution in response to light touch stimuli.
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