Fundamentals of Molecular Genetics - Assignment Example

A. What does heterozygous mean? What does homozygous mean? Please give an example (in regards to the above case). Answer: Heterozygous means the offspring having two different alleles for single trait. In simplified version any diploid organism having two different gene or alleles for single phenotypic characters is called heterozygous here if mice have Bb genotype than it is heterozygous for fur colour. While homozygous means having two same alleles for single trait, here id genotype of mice is bb or BB than it is homozygous for fur colour. B. Make a legend or KEY C. Which genotype dies? Please explain Answer: Mice having genotype of TTBb and TTbb will die as the dominant allele T for tailless is lethal in case of homozygous condition and both of these cases is homozygous for T. D. What is a genotype? What are the genotypes of the parents in the above cross? Answer: Genotype the genetic makeup of particular organism related to any visible of phenotypic characteristic. Here genotypes of both parents are TtBb and Ttbb. E. What does the F1 genotype look like? What is the ratio? Answer: The genotype of offspring will be TtBb, Ttbb, TTBb, and TTbb out of which mice having genotype TTBb and TTbb will die after birth. And ratio will be 6:6:2:2 F. What is a phenotype? What does the F1 phenotype look like in the above case? What is the ratio? Answer: The phenotype will be tailless black, tailless brown, tailed black and tailed brown in the ratio of 4:4:2:2 (excluding four genotype, which will die). G. Please draw out the punnent square of the above cross. How many squares are there? Answer: Punnent square (16 squares) TB Tb tB tb Tb TTBb TTbb TtBb Ttbb Tb TTBb TTbb TtBb Ttbb tb TtbB Ttbb ttBb ttbb tb TtBb Ttbb ttBb ttbb H. If you utilized the branch or tree method, do you get the same number of different possible combination. No there will not be any difference in combination. 2. What is a test cross? Please give an example. Test cross is genetic experiments where one can identify homozygous or heterozygous dominance of particular trait , for example if one can breed BB (black fur dominant) and bb (brown fur recessive). Here in F1 generation if all the mice were black than one can say Black characteristic is heterozygous dominant while if we get 50% of both the color than Black colour is homologues dominant. 3. What are co-dominant alleles? Please give an example and illustrate Co-dominance is condition where both alleles express and give phenotypic character to the individual. Classical example is AB blood group in human where both the alleles A and B for blood group express together. 4. What is incomplete dominance? Please give an example and illustrate. What is the main difference between co-dominance and incomplete dominance? Incomplete dominance is condition where recessive characteristics appear along with dominant one. For example in case of crossing between red (dominant)flower plant with white (recessive) plant give rise to pink flower as red is incomplete dominant alleles. The major difference between co-dominance and incomplete dominance is in case of co-dominance one can observed both characteristic on single individual for example in above mention case of flower breeding red and white flower will observed in case of co-dominance. While in incomplete dominance mixture of both the characters appears and hence one can see pink flower. 5. The pedigree below represents a genealogy containing the trait for albinism. When the trait appears, it is represented by a shaded symbol. What is the mode of inheritance? The mode of inheritance n Albinism is called “Autosomal recessive” inheritance as this trait is inherited by recessive alleles and express only in recessive homozygous individual 6. Can you name at least 1 other mode of inheritance? Sex linked inheritance is another type of inheritance where particular trait through sex chromosomes and there for two types of sex linked inheritance namely Y linked and X linked inheritance. The classical example is colour blindness in human. Essay: Who is Gregor Mendel? Why is he so important to Genetics? Please write at least 250 words or more. Gregor Johann Mendel was priest and scientist born on 20 July 1822 in Austria and known as father of genetics, He was the first to demonstrate the role of inheritance by extensive experimentation on pea plant. He demonstrated that inheritance follows certain laws and based on that one can predict outcome of breeding experimentation and those laws were given his name than after. The significance of Mendel’s work was not recognize till 20th century .After rediscovery of his work a new branch of biology was opened with name of “Genetics”. Mendel worked on a pea plant, Pisum sativum and studied inheritance of seed coat color, height of plant, shape of seed and flower colors. He did cross breeding of all these variety of pea plants in his garden for almost 7 years and came with conclusion that inheritance of particular trait follows certain numerical distribution. He also had given concept of recessive and dominant alleles or trait. His work was first time published as experiments with plant hybridization at two meetings of Natural History society of Brunn in Moravia in 1865. But most of his ideas were rejected and criticized. His work was sited only thrice in next 30 years but in 1900 Hugo de Vries and Carl correction rediscovered his work and replicated in lab. Similarly genetic basis of these observations was established in few years later. After combination of both statistical and biological aspect of Mendelian genetics by A.R.Fisher, Mendel’s observation was established as two laws of genetics namely Law of segregation and Law of independent assortment. Mendel’s pioneering work on genetic basis of phenotypic characteristic have immense important in present day scenario to. There are hundreds of diseases like hemophilia; albinism, color blindness etc can be predicted well in advance based on family history of offspring. It is widely used in plant hybrid and mutation breeding for high yield cultivars. Based on his work many new disease where identified which doe not follows Mendelian inheritance and group under non Mendelian diseases. In conclusion his work made him in real sense father of genetics. Week 2a Can you please outline what Meiosis and Mitosis is? How are these two similar and different? Please include what are the differences between spermatogenesis vs. Oogenesis? Meiosis is reduction cell division where number of chromosome reduced to half or form 2n to n. meiosis mainly occur in reproductive cells like spermatogenesis. While mitosis is process of cell division where total number of chromosomes. Mitosis mainly occurs in all somatic cells and helps in increasing cell number or replacing old one. The major differences between spermatogenesis and oogenesis is unequal cytokinesis in Oocyte while spermmetocyte developed by equal cytokinesis. Secondly 4 sperm cells developed form single spermatocytes while single Oocyte developed in to single ovum. Week2b As we discussed in Class, can you tell me who Morgan is, what is he famous for and how he changed the outlook for Mendelian Genetics? Answer: Thomas Hunt Morgan was an American geneticist worked on inheritance in fruit fly. He discovered that gene or alleles are located on chromosome and which inherited from parents to children. He won Nobel Prize in 1933 for his discovery of chromosome. The main contribution of his work toward Mendelian genetics. He established the role of genetic material and explained how particular genotype and phenotypes transfers from inherited form one generation to other. Week3: Explain in your own words what Mendels two Laws (1st law and second law) are and give an example of each. Answer: The first law of Mendel coined new terms called alleles and alleles are nothing but two different form of single gene. Every individual have two alleles for particular gene and both get segregated during reproduction. The second law says that if we consider two trait or characters of individual then the inheritance of one character will not influence by inheritance of other. Read More