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:
Fairy penguins (Eudyptula minor), also known as little penguins, are tiny, slate-blue animals found along the coastlines of southern Australia and New Zealand. Not only are they more colorful than most aquatic birds, but they're also notably smaller, growing to be less than a foot tall and about 2.5 pounds.
Answer:
Ans - 1 Photosynthesis begins with the light reactions. It is during these reactions that the energy from sunlight is absorbed by the pigment chlorophyll in the thylakoid membranes of the chloroplast.
Ans-2 The dark reactions of photosynthesis occur in the stroma of the chloroplast where they utilize the products of the light reaction. In the dark reaction, plants use carbon dioxide with ATP and NADPH from the light reactions to produce glucose.
Ans-3 The main factors affecting rate of photosynthesis are light intensity, carbon dioxide concentration and temperature.
During the 32nd week of gestation, good luck!
