The randomness in the alignment of recombined chromosomes at the metaphase plate, coupled with the crossing over events between nonsister chromatids, are responsible for much of the genetic variation in the offspring. To clarify this further, remember that the homologous chromosomes of a sexually reproducing organism are originally inherited as two separate sets, one from each parent. Using humans as an example, one set of 23 chromosomes is present in the egg donated by the mother. The father provides the other set of 23 chromosomes in the sperm that fertilizes the egg. Every cell of the multicellular offspring has copies of the original two sets of homologous chromosomes. In prophase I of meiosis, the homologous chromosomes form the tetrads. In metaphase I, these pairs line up at the midway point between the two poles of the cell to form the metaphase plate. Because there is an equal chance that a microtubule fiber will encounter a maternally or paternally inherited chromosome, the arrangement of the tetrads at the metaphase plate is random. Thus, any maternally inherited chromosome may face either pole. Likewise, any paternally inherited chromosome may also face either pole. The orientation of each tetrad is independent of the orientation of the other 22 tetrads.
Explanation:
The sclerenchyma is the tissue in which creates the plant firm and hard. The two kinds of sclerenchyma cells exist fibers and sclereids. Their cell walls be made up of cellulose, hemicellulose and lignin. The sclerenchyma cells are the principal associate cells in plant tissues that have come to a close elongation.
As food moves through the digestive tract, it spends the most time in the large intestines. This is because of the need to absorb water and partially digest fiber.
<span>How can a mutation in a DNA base sequence cause a change in a trait?</span>
