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:
On the islands of the Galapagos lives a group of birds called finches. There are 13 species in this group. These species have diverse ecologies--some eat seeds, some eat insects, some eat fruit, and some even eat cactus. Although the bodies of these species look fairly similar, their beaks are very different. That is because it is their beak that is adapted to these diverse ways of feeding (Figure 8.14).
Answer:
1. Scientific method
2. pseudopods
3. In 1909, Ernest Rutherford’s
4. innovation
5. nerve cell
A contusion occurs when a strong blow or repeated blows from an object struck the body, crushing the underlying muscle fibres and connective tissues without breaking the skin.
A contusion can vary in severity depending on the object and location of the injury. For example a contusion to the brain may cause a concussion that can cause serious symptoms that require immediate medical attention
