Answer:
oligodendrocytes
Explanation:
Glial cells are part of the nervous system. These are helper cells that support the function of the central nervous system (CNS) and can be called oligodendrocytes when they supply myelin to neurons. These cells are responsible for producing the myelin sheath have the function of electrical insulator for CNS neurons. They have extensions that wrap around the axons, producing the myelin sheath.
It is estimated that there are 10 glia cells in the CNS for each neuron, but because of their small size, they occupy half the volume of nervous tissue. They differ in form and function and they are: oligodendrocytes, astrocytes, Schwann cells, ependymal cells, and microglia.
Answer: Crossing-over allows the genes that come from each parent to recombine before they are passed on to future generations because chromatids of homologous chromosomes mate and exchange sections of their DNA.
Explanation:
Chromosome crossing-over is the process by which chromatids of homologous chromosomes mate and exchange sections of their DNA during prophase I of meiosis, when pairs of homologous chromosomes, or of the same type, are aligned. The chromatids of the homologous chromosomes break off in the chiasmas and rejoin to allow recombination of the linked genes. So it occurs when regions at chromosome breaks mate and then reconnect to the other chromosome. <u>The result of this process is an exchange of genes, called genetic recombination</u>.
This allows the genes that come from each parent to recombine before they are passed on to future generations. Then, <u>it is an important source of genetic variability</u>, since it involves an exchange of segments between homologous chromosomes during the development of gametes. <u>This process allows that the descendants of an individual are genetically very different</u>, since it is very unlikely that an individual produces two equal gametes, because all of them have different segments of the homologous chromosomes.
it is a barrier with tiny openings that lets some ,but not all, matérials pass through
