Genetic Engineering Research Assignment Paper (Term Paper Sample)

Genetic Engineering
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Part One
Cell division
Question (1a).
Question (1b).
Anaphase II
Telophase I
(3) Meiosis takes place in two distinct stages; the first stage involves; Interphase I, this step includes the replication of the cell chromosomes (Hunt and Hassold 2002, p. 2182). Prophase I, the chromosomes thicken and shorten, the homologous chromosomes align side by side forming bivalents. The chromatids remain in contact at the chiasmata where the exchange of genes occurs. In the stage of metaphase I, the cellular homologous chromosomes translocate to the equator while attached to the spindle fibres at the centromere. In anaphase I, the homologous chromosomes move to the opposite poles due to the shortening of spindle fibres. The second stage of meiosis involves; Interphase II, the stage comprises the duplication of cellular chromosomes, this step is followed by prophase II which includes the formation of new spindle fibres. In metaphase II phase, the cellular chromosomes move towards the equator. In anaphase II stage, the sister chromatids within the cell detach and migrate towards the poles, this movement is brought about by the restriction of the spindle fibres. Finally, in telophase II, the sister chromatids reunite to form chromosomes and take the thread-like patterns (Turnpenny and Ellard 2011, p. 245).
Diagram
Question (1c).
1: Interphase, 2: Prophase, 3: Metaphase, 4: Anaphase, 5: Telophase
Explanation (1c)
Mitotic cell division leads to the formation of two daughter cells that have the same number of chromosomes similar to that of the parent cell (Nigg 2001, p. 25). This process is crucial since it ensures that every cell contains the same number of chromosomes as those of the parent. The mitotic stages occur in a sequential manner in that one stage leads to the other without the interference of activities within the cell. In the above onion cell, part labelled (a) is interphase; this stage involve the duplication of genes so as the resulting daughter cells can have the same number of chromosomes as those of the parent.
Likewise, this step entails the synthesis of new cell organelles within the cell such as mitochondria and centrioles (Adams, Carmena and Earnshaw 2001, p.51). Lastly, in interphase, the cell starts to accumulate energy reserves that mainly (ATP) to drive the dividing cells through the whole process of cell division. Part labelled (b) is prophase; the stage involves the duplication of centrioles with the formation of spindle fibres. Similarly, the plasma membrane starts to disintegrate with the subsequent disappearance of the nucleolus. Consequently, the stage is characterized by the thickening and the shortening of the chromosomes, the chromosomes take the form of stains which are visible and each chromosome at this point are marked by chromatids linked together at the centromere.
The part labelled (c) is metaphase; in this stage, the nuclear membrane disappears and thus the chromosomes become free within the cytoplasm. Furthermore, the phase is distinguished by the lengthening of the spindle fibre which attaches with the centrioles at both poles. Similarly, the chromosomes align themselves along the equator while connected to the spindle fibres. The part labelled (d) is anaphase, at this stage; the chromatids begin to detach and move towards the opposite poles, this movement is caused by the subsequent shortening of the spindle fibre and ultimately disappear. The part labelled (e) is telophase, in this stage, the chromatids accumulate at the opposite end of the spindle, this step is followed by the formation of a nuclear membrane; similarly, the cytoplasm divides into two halves leading to the formation of two daughter cells.
Question 2
To observe the stages of mitosis, one needs to have an onion bulb obtained from the root tip, distilled water, a beaker, 1M HCl acid the acetic-orcein stain. Similarly, one must have microscope slides and the cover slips, a filter paper, a source of heat such as the Bunsen burner, the scalpel and the watch glass. Place two molar HCl on the watch glass and add two drops of acetic-orcein stain. Cut 2mm of an onion root and deep it in the acid mixture. Gently warm the content in the watch glass afterward, transfer the root tip onto a glass slide. Using a scalpel macerate the specimen on the slide and place a cover slip. Place the slide containing the specimen between the filter papers and apply some pressure carefully to form a thin squash, put the slide on the stage of the microscope and then observe the onion specimen under low power objective and then carefully shift to the medium power magnification and compare with the photomicrograph
The zones of the root tip can be divided into four regions, at the tip end is the root cap that protects the entire root against mechanical damage. Similarly, the columella cells found at the root cap are responsible for gravity detection. The cells can as well respond to light and pressure that result from the soil. As growth progresses, the columella cells are pushed towards the periphery thus forming the peripheral cells which produce a substance known as mucigel that is responsible for the protection against mechanical damage as the root pushes through the soil. These cells as well help in the prevention of desiccation (Gregory 2008, p.32).
The mucigel cells also contain a lubricating substance that lubricates the root as it pushes grows into the soil. Immediately after the root cap is the apical meristem which originates from the embryonic cells which are divided into three main parts namely, the cell division zone which comprises of cells that are actively dividing. The cells at this region are characterized by a thin cell wall, absence of vacuoles and dense cytoplasm. The zone of cell expansion or elongation comprise of cells that are enlarged to their optimum size, the presence of vacuoles as well characterizes these cells. The region of cell differentiation comprise of cells that have attained their permanent size; these cells are characterized by the presence of vacuoles that have thick walls, these cells as well differentiate into permanent tissues such as the xylem and the endodermis that are found on the roof of the plant (Gregory 2008, p.33).
In prophase, the chromosomes, the chromosomes becomes shorter and thicker, they as well become stained and thus appear visible. The chromosomes correspondingly develop and appear as a pair of chromatids that are joined at the centromere. In metaphase, the chromosomes align at the equator and attach to the spindle fibres at the centromere region. Lastly, in anaphase, the chromosomes detach at the centromere and start to migrate towards the opposite poles; these movements to the poles are as a result of the shortening of the spindle fibres (Schwarzacher, 2012, p. 55).
Part two
Question 1
Genotype: these are the genes that are present in an organism, in other words, these are the genetic composition of an individual.
Phenotype: This is the observable traits in an individual; it involves the expression of a genome in the appearance and structure of an organism.
Monohybrid comprises of a single trait in an organism that is presented in a homologous chromosome by a pair of genes.
A dihybrid is a heterozygous hybrid of two dissimilar genes.
Question 2
The dominant characteristic is green (green podded peas)
The ratio of green podded peas as compared to yellow is 3:1, that is 3 green: 1yellow
The genotypic ratio: 1GG: 2Gy: 1yy. The phenotypic ratio: 1 homozygous: 2 heterozygous green: 1 homozygous yellow
Question 3
The ratio of the offspring’s phenotype is:
* 8 Black short-tailed: 2 Black long-tailed: 4 White short-tailed: 2 White long-tailed
* Since the dogs have been producing white and black puppies, black is dominant while white trait is recessive because black puppies are the majority in number (25).Therefore, the genotype for black heterozygous (Bb). Equally, both dogs produce both long haired and short haired puppies of which the short haired puppies are the majority (23). This means the short haired genes are dominant and heterozygous over the long haired (Ss).
The parental genotypes, therefore, are: (BbSs xBbSs)
(B-Black, b-white, S-short, s-long)

BS

bs

bS

bs

BS

BBSS

BbSs

BbSS

BbSs

Bs

BBSs

Bbss

BbSs

Bbss

bS

BbSS

bbSs

bbSs

bbSs

bs

BbSs

bbss

bbSs

bbss

Question 4
(a) Cystic fibrosis disease is caused by a recessive allele, to develop the disease you need to inherit a pair of the defective allele. If the copy inherited is one, then you will not suffer from the disease, but you become a career. In this case, both parents are carriers and they will not show any symptom of the disease in their lifetime. However, one of their children will be formal, two will be carriers and one will suffer from the disease (Drumm et al. 2005, p.1445.
Punnet square illustration: f signifies the gene responsible for Cystic Fibrosis
(c) Huntington’s syndrome is brought about by a dominant gene that critically impairs the human nervous system; the disease can be passed from one parent to the offspring and thus posing a threat considering that there is no medication for the disorder. Genetic testing can predict if one is likely to develop the disease since those at risk have an expanded CAG repeats. Therefore, if one has an expanded CAG repeats, he or she is likely to develop neurological symptoms at any age of life and this is unethical since one has to coup with the result of developing the disease that has no treatment. However, it is essential to know the state ...