Answer:
The homologous chromosomes pair together in prophase 1 of meiosis, but they do not during prophase 1 of mitosis. This is achieved by a process known as synapsis, where the similar chromosomes pair according to sequence similarity. The homologous chromosomes are held together by a protein structure known as the synaptonemal complex in a chromosome body known as a tetrad (because it contains 4 replicated chromosomes known as chromatids) or bivalent (if the organism is diploid). This pairing during prophase 1 of meiosis allows recombination to take place between the homologous chromosomes. This occurs early during prophase but the manifestation of recombination only becomes visible during the later stages of prophase 1 and in metaphase 1. Because the chromosomes adopt different structures during prophase 1 of meiosis, this stage is sub-divided into 5 stages: leptotene, zygotene, packytene, diplotene and diakinesis. It is during diplotene and diakinesis that the physical manifestation of recombination can be seen. This is the presence of chiasmata (chiasma, singular). These are the sites where recombination, or exchanges between homologous chromosomes, has taken place. By the end of prophase 1, it is only the chiasmata that holds the homologous chromosomes together. This constriction make the tetrads adopt a variety of structures, the shape of which depends upon the number of chiasmata formed. The tetrads stay in this conformation until metaphase 1. Synapsis, the formation of the synaptonemal complex, the formation of chiasmata does not take place during prophase 1 of mitosis and these processes represent the major differences between prophase of the two nuclear divisions.
Answer:
B. interconnected
Explanation:
All the systems in our bodies (humans are indeed animals) are connected with each other to create a functional being. The blood flows throughout the body, providing nutrients; the bones support the structure and protect the heart and lungs. They work together.
Why not A: The systems are all completely necessary. There's nothing extraneous in our bodies, because extraneous stuff takes up energy, and our biology is incredibly economical.
Why not B: They're not interchangeable. How would you like your bones to turn to blood? Uh-huh.
Why not D: They interact with each other consistently, so they're not separate or segregated.
Phosphorus: a vital source of animal nutrition. Phosphorus is one of the most important minerals in animal nutrition. It is the second most abundant element in an animal's body after calcium, with 80% of phosphorus found in the bones and teeth, with the remainder located in the body fluids and soft tissue.
Answer:
An enzyme is a protein. Any change in the primary structure of a protein (the primary structure is the aminoacid sequence) can induce a change in the secondary, as well as tertiary structure (tridimensional conformation). This change in the shape of the enzyme can affect its activity, since it can change the active site consequently to this conformational change.
Explanation:
Answer:
RBCs' production is controlled by erythropoietin.
Mature RBCs are released into the bloodstream after approximately seven days RBCs are produced in the bone marrow
Explanation:
The hormone erythropoietin is produced and released in the bloodstream by peritubular interstitial cells of kidneys. The function of erythropoietin is to increase the number of the precursors of red blood cells and thereby to stimulate the production of red blood cells in the bone marrow. When the oxygen supply to body cells is reduced, the hormone erythropoietin stimulates the development of proerythroblasts into reticulocytes and thereby increases the RBC production.
RBCs are produced by the process of erythropoiesis and take about seven days to become mature and to be released in circulation to serve the function of oxygen delivery. The maturation of RBCs also includes the loss of most of the organelles such as the nucleus and mitochondria to accommodate hemoglobin protein. The life span of circulating RBCs is about 100-120 days.
