Difference between Oncogenes and Proto-Oncogenes - Assignment Example

Chapter 11 What is the difference between oncogenes and proto-oncogenes? Proto-oncogenes are genes which are normally present in cells and carry out diverse functions including transmission in the process of cell division, apoptosis, senescence etc. Due to some chemical of physical agents called mutagens these proto-oncogenes are converted to oncogenes. Oncogenes are responsible for uncontrolled proliferation of cells leading to the formation of tumor. Chapter 8     1. There are three stages during interphase. What are they and what is happening in the cell during each stage. Interphase or the resting phase is the initial stage of cell division when the cell prepares itself for cell division. It is the longest phase of the cell cycle and involves three stages- G1 phase- or the growth phase where the cell and its cytoplasm grows and increase in size. Cell function normally. Growth is associated with the protein formation and so the cell synthesize all the required proteins for division. Synthesis or S-phase where the synthesis of DNA occurs. The DNA undergoes replication and hence prepares the cell for division. G2-phase or another growth phase where the cell grows in size and forms numerous protein molecules. These proteins are required for cell division and involves, microtubules and spindle fibres.     2. Explain why, knowing the basis of meiosis, why you may have features similar to a sibling or parent but you are not exactly the same. Meiosis involves pairing of homologous chromosomes. When paired chromosomes come close they cross-over at certain point or points leading to the formation of "chiasma". Here exchange of genetic material takes place. This is one of the biggest reasons that although we bear the genes of our parents and even our siblings also bear the genes of the same parents but they are different. Since crossing-over varies in different cell division and hence there is a variation in the genetic makeup of the siblings and also between the parents and siblings.     3. What is karyotyping and how would this information be useful in the medical world. Give an example. Karyotyping is related to the number of chromosomes present in an organism. It is concerned with the appearance of chromosomes in the nucleus of eukaryotic cells. It is important to find out the presence of any genetic abnormality. For example- An individual having Downs Syndrome will have three copies of the 21st chromosome which could be detected with the help of karyotyping when chromosomes will be arranged. This is the reason why Down Syndrome is also known as Trisomy (three copies) of 21st chromosome. The total number of chromosomes in case of human is 46 but in case of patient with Trisomy, the number is 47.     4. Explain the difference between a diploid and haploid cell. Every organism possess specific set of chromosomes. A diploid cell has two set of chromosome, one called the maternal set of chromosome (obtained from mother) the other called paternal chromosome (obtained from father). Haploid cell has only one set of chromosomes.   Chapter 9     1. A true breeding brown mouse is mated with a true-breeding white mouse and all their offspring are brown. If two of these brown offspring are mated, what percentage of the F1 and F2 generations will be brown? The true breeding brown mouse has dominant gene for the color (BB) while the true breeding white mouse has recessive genes for color (bb). As per the Mendels Law of Dominance, only the dominant character is expressed, when these two mouse are crossed then the first filial generation or the F1 generation is Brown with the genotype of Bb, since brown is the dominant color. BB X bb = Bb When the progeny of the F1 generation are crossed, according to Mendels Law of Segregation, the genes segregate and therefore the second generation will have brown and while mouse both. Bb X Bb = 1 BB, 2 Bb, 1 bb indicating the Phenotypic ratio as 3:1 while the genotypic ratio is 1:2:1.     2. Define the following:         a. gene- Gene is the basic unit of heredity that is transferred from one generation to another i.e. it is transferred from parents to the offspring. It is a sequence of nucleotides.         b. allele- It is the genetic alternative of the gene (one from the pair). Allele is located at a particular locus on the chromosome.         c. dominant- The character which appears in the allelic combination. It masks the presence of its recessive counterpart. e.g. Bb- will have brown color due to the presence of dominant form B.         d. recessive- The character which does not make its appearance in the presence of its dominant counterpart in the allelic combination. It is expressed only in homozygous condition. In Bb, recessive character b is masked and so the skin color is brown while in bb the skin color is white due to the expression of the recessive form.         e. genotype- The genetic make-up of the individual or the organism is its genotype.         f. phenotype- The external appearance of the individual is its phenotype.         g. homozygous- When both the allelic forms on the chromosomal set are same they are said to be homozygous, e.g. BB is brown and is homozygous, bb is white and is also homozygous. They form the same set of gametes. B         h. heterozygous- when both the allelic forms on the chromosome set are different they are said to be heterozygous, e.g.  Bb is brown color but it is heterozygous. They form two different kinds of gametes B and b. Lab 6  Microbiology 1. What is a pathogen? Pathogen is a micro-organisms capable of causing disease condition. E.g. Bacteria, virus, protozoa, fungi, prion etc. 2. Are all bacteria pathogenic? If not, what are some beneficial uses of bacteria in food production, medical (pharmaceutical) and part of the human flora? No not all bacteria are pathogenic. Nitrosomonas is anitrogen fixing bacteria present in the root nodules of legumes. It converts the atmospheric nitrogen into nitrate which can be utilized by plant for the protein synthesis. Lactobacillus is used for the production of curd in food industry, lactic acid in pharmaceutical industry. E. coli present in the human gut produces essential vitamins and maintains normal flora of the gut. If this microflora is destroyed the person may have indigestion (one of the side-effects of antibiotics). 3. What are viruses? Provide some detail as to their structure. Virus is an infectious agent, that is considered to be the connecting link between living and non-living world. It does not have any cellular machinery, instead it contains genetic material surrounded by a protein coat and a few enzymes. The genetic material is either DNA or the RNA and never the both. Most of the plant virus are RNA virus while most of the animal virus with a few exceptions are DNA virus. It requires host cell machinery for replication and multiplication. Once the genetic material of the virus enters the host cell it takes the command on the cellular machinery and replicate (make identical copies). It burst opens the host cell and attack the neighboring host cells, this is how it causes infection.   Read More