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Question 1: Significance of differences between mitosis and meiosis

Mitosis and meiosis are the two major processes by which eukaryotic cells reproduce. Compare and contrast the processes of mitosis and meiosis. Consider the stages involved in each and their eventual products. How are the differences biologically significant relative to growth and reproduction? Be prepared to discuss how life is dependent upon both types of cellular reproduction.

Respond to the following posts in relation to the above question, please include references.

1. David

A: Both mitosis and meiosis are associated with cytokinesis. The result is that both daughter produced parent cells. The fundamental sequences in mitosis is the same as meiosis (meiosis happens twice). Both process include the breakdown of nuclear membrane, separation of genetic material into two groups, followed by cell division, and reformation of the nuclear. Meiosis has two rounds of genetic separation whereas mitosis has one. Chromosomes of the meiosis homologous separate to the daughter cells that are not identically. Daughter cells are identically to the parent cell in mitosis.

2. Kelly

The function of mitosis is the regeneration of new cells while the function of meiosis is the production of gamete cells for sexual reproduction. Mitosis produces two identical daughter cells during the different phases; Prophase, Prometaphase, Metaphase, Anaphase, and Telophase. Meiosis produces four cells that aren't identical. Mitosis has four phases while meiosis has eight phases. Crossing over cannot occur in mitosis but can occur in meiosis. "The main differences between mitosis and meiosis occur in meiosis I. In meiosis I, the homologous chromosome pairs become associated with each other and are bound together with the synaptonemal complex ("Boundless,"2016). Meiosis and mitosis are important because they are the process of cell division, and without it living things wouldn't grow. Also cells wouldn't be able to reproduce themselves.

References

Boundless (2016). Boundless Biology. Retrieved from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/meiosis-and-sexual-reproduction-11/the-process-of-meiosis-92/comparing-meiosis-and-mitosis-406-11633/

3. Camilya

During mitosis is a process of reproduction cells are duplicated and divided to create daughter cells. These cells contain the same DNA as the original cell. The mitosis process has 4 stages prophase; metaphase; anaphase; and telophase. In the prophase chromosomes become visible under the light microscope. The stops all other process and prepares for mitosis. The chromosome aligns itself with the middle of the cell in order to be divided equally. Chromosomes are divided during the metaphase, after chromosomes have been aligned; they begin to separate, entering the anaphase. The cell develops two Polar Regions located at the opposite ends of each cell; microtubules then connect chromosomes at the Polar Regions, and chromosomes pulls toward the poles. During this step the chromosomes each travel to a different pole. After chromosomes have separated they begin to uncoil, and nuclear envelope starts to reform which is now a part of the Telophase. Once the chromosomes have fully separated the mitosis process is complete.

Meiosis

Meiosis is a two stage process where sex cells are formed. A single cell is divided twice to produce four cells that will contain only half of their original DNA. Stage one interphase, Prophase I, Metaphase I, Anaphase I, and Telophase I and cytokinesis. Stage two of Meiosis prophase II, Metaphase II, Anaphase II, and Telophase II and cytokinesis

Stage I

Interphase is where the cell DNA is copied creating identical chromosomes. The Prophase contract the copied chromosomes into X-shaped structures that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids containing identical genetic information. The chromosomes link up so that both replicas of chromosome 1 are together, b and the replicas copies of chromosome 2 are together, and so on. The chromosomes then cross over. Metaphase the form a line along the cell, centrioles are at opposite ends of the cell with meiotic spindles extending from them, and the meiotic spindle fibers attached to the chromosome. Anaphase chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole. In meiosis I the sister chromatids stay together. This is different to what happens in mitosis and meiosis II. Telophase I and cytokinesis is where chromosomes complete their move to the opposite poles of the cell. A membrane forms around the chromosomes creating two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.

Meiosis II

Prophase the daughter cells contract into visible X-shaped structures. The membrane dissolves away releasing the chromosomes, centrioles duplicate and the meiotic spindle forms again. Metaphase II the daughter cells form a line along the equator of the cell. Centrioles appear opposite to daughter cells on poles and meiotic spindle fibers are attached. Anaphase II sister chromatids are then pulled to opposite poles due to the action of the meiotic spindle, and chromatids are now individual chromosomes. Telophase II and cytokinesis chromosomes travel to opposite poles of the cell and a full set of chromosomes gather together, then a membrane forms. Cell division is complete when there are four granddaughter cells.

Reference:

“What is meiosis “Retrieved from http://www.yourgenome.org/facts/what-is-meiosis

Simon, E. J., Dickey, J. L., Reece, J. B., Hogan, K. A. (1--2015). Campbell Essential Biology with Physiology, 5th Edition. [South University]. Retrieved from https://digitalbookshelf.southuniversity.edu/#/books/1323125574/

Question 2: Mendel’s Principles

Mendel used mathematics and experimentation to derive major principles that have helped us understand inheritance. His ideas were totally different than the explanation for passage of characteristics from parents to offspring that was common to his time. List and describe his principles and describe how each contributes to genetic variability. How might biology have be different if his discoveries had not been lost for decades? Be prepared to discuss the significance of Mendel’s discoveries to modern biology.

Respond to the following posts in relation to the above question, please include references.

1. Camilya

Mendel used the rubrics of probability to forecast the results of his breeding experiments. He compared precise quantities of offspring to the predicted amount of offspring according to probability. Some of Mendel’s probabilities were confirmed but a few were not, the uncertainty of Mendel’s other predictions caused him to search harder as a result he created Those that did not work out as predicted were perhaps the most important because they caused him to this principles of inheritance.

Mendel discovered the fundamental laws of inheritance after his observation on pea plants. He uncovered that genes come in pairs inherited from parents DNA. Mendel tracked the separation of parental genes and their appearance in the offspring, determined that mathematical patterns were the source of inheritance from one generation to the next. Mendel created three Laws, The Law of Segregation, and The Law of Dominance, and The Law of Independent Assortment.

The law of segregation explains that only one of the two genes are present organism in the offspring, and the determining factor is random. During fertilization where and egg and sperm joined together a new organism is created, and its genotype has the same contents of gametes. Mendel's law of independent assortment states that one gene does not influence the allele received for another gene. Mendel's law of dominance explains that in a heterozygote, one trait will cover the presence of another trait for the same characteristic.

Reference:

Khan Academy(2016) “Introduction to Hereditary retrieved from https://www.khanacademy.org/science/biology/classical-genetics/mendelian--genetics/a/probabilities-in-genetics

Source: Boundless. “Mendel's Law of Dominance.” Boundless Biology. Boundless, 26 May. 2016. Retrieved 04 Dec. 2016 from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/mendel-s-experiments-and-heredity-12/laws-of-inheritance-96/mendel-s-law-of-dominance-420-11647/

2. Javier

If two pure breeds cross for a particular character, the descendants of the first generation are all equal to each other and, in turn, equal to one of their progenitors, who is the possessor of the dominant allele. Mendel elaborated this principle by observing that if he crossed two pure races of pea plants, one of yellow seeds and one of green seeds, the offspring he obtained, which he called F1, consisted only of plants that produced yellow seeds. These plants had to have, in the gene that determines the color of the seed, the two alleles they had inherited from their parents, one allele for the green color and one for the yellow color; But for some reason only the latter was manifested, so it was called the dominant allele, while the former was called the recessive allele.

Mendel's Second Law

Recessive alleles that, when crossing two pure breeds, do not manifest in the first generation (denominated F1), reappear in the second generation (denominated F2) resulting from crossing the individuals of the first. In addition, the proportion in which they appear is of 1 to 3 with respect to the dominant alleles. Mendel crossed among the peas of yellow seeds obtained in the first generation of the previous experiment. When he classified the resulting offspring, he observed that about three-quarters had yellow seeds and the remaining fourth had green seeds. That is to say, the character "seed of green color", which had not appeared in any plant of the first generation, did appear in the second but in less proportion than the character "yellow seed"

Third Mendel law

The characters that are inherited are independent of each other and are combined at random when passing to the offspring, manifesting in the second filial generation or F2. In this case, Mendel selected for the crossing plants that differed in two characteristics, for example, the color of the peas (green or yellow) and their surface (smooth or wrinkled).

He observed that the first generation was composed only of plants with yellow and smooth peas, fulfilling the first law. In the second generation, however, all possible combinations of characters appeared, albeit in the following proportions: 1/16 part of green and rough peas, 3/16 of green and smooth, 3/16 of yellows and rough, and last 9 / 16 yellow and smooth. This led him to think that the genes were structures independent of each other and, therefore, that only depended on chance the combination of the same that could appear in the offspring.

Thanks to the good education that Mendel received, despite being the son of poor peasants in Silesia, he was able to graduate and teach physics and natural sciences. During these years, ideas about the origin of species disturbed many naturalists and scientists not only in Europe, but in America, a concern Mendel had not escaped. Some of his direct teachers, like the Viennese botanist Franz Unger, supported the idea that varieties appear in nature and that with the passage of time and only some of them, after many generations become well differentiated species. Thanks to this idea transmitted by his teachers, Mendel believed that he could find the answer to the origin of the species if he studied closely the problem of variations in nature.

From the laws of Mendel is that modern genetics was built during the present twentieth century, since while Mendel lived were not welcomed.

References

Simon, E. J., Dickey, J. L., Hogan, K. A., & Reece, J. B. (2015). Campbell Essential Biology with Physiology (5th ed.). New York, NY: Pearson Education Inc.

Lonnig, W.E. (2001) John Gregor Mendel: Why His Discoveries were Ignored for 35 (72) Years. Retrieved from http://www.weloennig.de/mendel02.htm

3. Angela

Mendel's law of segregation: this law states that during the gamete formation, pairs of alleles segregate and then during the fertilization the alleles become fused together again. Law of independent assortment: simply put the inheritance of one trait is not dependent upon another. For example, a person being brown eyed has no baring upon whether they will have red hair or blonde hair. Rules of probability: Mendel was a mathematician and understood the probability of occurrences. He applied this principle to genetic crosses. For example (as the book used this one) in dog breeding if a black lab is bred with a chocolate lab he said that the probability of getting a chocolate was independent of getting a black lab. The coin toss is a much better example as each toss of the coin will produce either a head or a tail. Each time the coin is tossed the chance of getting a head 1/2. It doesn't matter how many times the coin is tossed or how many heads turn up, each toss has the same probability of 1/2. No matter how many children two people have the probability of them having a child with brown eyes or blue eyes remains the same. It is a shame his work was lost for so long. If it had not been lost biologists or scientists would hve discovered certain diseases or could have predicted things about the children a woman was carrying. Or better yet, would have helped them to solve certain mysteries such as what causes children to be born with Down syndrome. I am not sure exactly what modern biology would be like now other than perhaps it would not have taken as long to get where it is now. Thanks, Angela Reference

Simon, E. J., Dickey, J. L., Reece, J. B., & Hogan, K. A. (2016). Campbell Essential Biology. Retrieved from https://digitalbookshelf.southuniversity.edu/#/books/1323125574/outline/13!/4/2/16/12/8/4@0:50.9