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.
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Answer:
Negative; Estrogens and progesterone
Contraceptive pills mimic the negative feedback effect of estrogens and progesterone.
Explanation:
- <em><u>Estrogens and progesterone are regulated by negative feedback mechanisms, and therefore, birth control pills make use of this fact.</u></em>
- <em><u>Birth controls pills adds extra amount of estrogen and progesterone which inhibits the release of these hormones by the body.</u></em>
- Consequently the release of an egg from the ovary is inhibited and the lining of the uterus is made to become thin and unsuitable for pregnancy by the absence of progesterone hence decrease the secretion of the luteinizing hormone and the follicle stimulating hormone by negative feedback.This process ends up inhibiting ovulation.
Answer:
Explanation:
Components of our Watershed
Wetlands. A wetland is an area of land that is saturated with water for all or part of the year. ...
Riparian Vegetation. The plants that grow along or near the riverbanks, lakes and wetlands are called riparian vegetation. ...
Uplands. ...
Groundwater.
Answer:
1In a hypothetical food chain consisting of grass, grasshoppers, sparrows, and hawks, the grasshoppers areprimary consumers. primary producers
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