Advanced Biotech Miscellaneous
- Determine the correctness or otherwise of the following Assertion (a) and the Reason (r)
Assertion : Somatic embryogenesis in plants is a two step process comprising of embryo initiation followed by embryo production.
Reason : Embryo initiation is independent of the presence of 2, 4 dichlorop-henoxyacetic acid whereas embryo production requires a high concentration of 2, 4-dichloroph-enoxyacetic acid.
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Somatic embryogenesis is a process where a plant or embryo is derived from a single somatic cell or group of somatic cells. Somatic embryos are formed from plant cells that are not normally involved in the development of embryos, i.e. ordinary plant tissue. In plants, somatic embryogenesis comprises of embryo initiation followed by embryo production.
Embryo initiation occurs on a medium rich in auxin, which induces differentiation of localized meristematic cells. The auxin typically used is 2,4-Dichlorophenoxyacetic acid (2,4-D). thus embryo initiation is dependent on 2,4-D. While these are transferred to a medium containing low or no auxin, then embryo production does not require high concentration of 2, 4-D. Correct Option: C
Somatic embryogenesis is a process where a plant or embryo is derived from a single somatic cell or group of somatic cells. Somatic embryos are formed from plant cells that are not normally involved in the development of embryos, i.e. ordinary plant tissue. In plants, somatic embryogenesis comprises of embryo initiation followed by embryo production.
Embryo initiation occurs on a medium rich in auxin, which induces differentiation of localized meristematic cells. The auxin typically used is 2,4-Dichlorophenoxyacetic acid (2,4-D). thus embryo initiation is dependent on 2,4-D. While these are transferred to a medium containing low or no auxin, then embryo production does not require high concentration of 2, 4-D.
- Identify the CORRECT statements
P. 5′ and 3′ ends of the transcripts can be mapped by utilizing polymerase chain reaction
Q. S1 nuclease can cleave the DNA strand of a DNA-RNA hybrid
R. T4 polynucleotide kinase is used for labeling 3′ end of DNA
S. Baculovirus (Autographa californica) can be used as an insect expression vector
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Rapid amplification of cDNA ends (RACE) polymerase chain reactions (PCR) are used for independent high-throughput verification of transcriptional starting sites (TSSs) determined by genome-wide assays. 52 -RACE PCR is a well-established and widely used method to specifically amplify the 52 end of a transcript, facilitating mapping of the TSS and the approximate location of promoter elements. Conventionally, this mapping is done by cloning the 52 -RACE PCR product into a bacterial vector and sequencing a few clones by classic electrophoresis-based Sanger sequencing. Now-a-days, even 3’ end transcripts are being mapped using 3’-RACE PCR. Baculoviruses are a very diverse group of viruses with double-stranded, circular, supercoiled genomes, with sizes varying from about 80 to over 180 kb which encode between 90 and 180 genes. Baculoviruses have evolved to initiate infection in the insect midgut. Baculovirus-insect cell expression systems have the capacity to produce many recombinant proteins at high levels and they also provide significant eukaryotic protein processing capabilities.
Correct Option: C
Rapid amplification of cDNA ends (RACE) polymerase chain reactions (PCR) are used for independent high-throughput verification of transcriptional starting sites (TSSs) determined by genome-wide assays. 52 -RACE PCR is a well-established and widely used method to specifically amplify the 52 end of a transcript, facilitating mapping of the TSS and the approximate location of promoter elements. Conventionally, this mapping is done by cloning the 52 -RACE PCR product into a bacterial vector and sequencing a few clones by classic electrophoresis-based Sanger sequencing. Now-a-days, even 3’ end transcripts are being mapped using 3’-RACE PCR. Baculoviruses are a very diverse group of viruses with double-stranded, circular, supercoiled genomes, with sizes varying from about 80 to over 180 kb which encode between 90 and 180 genes. Baculoviruses have evolved to initiate infection in the insect midgut. Baculovirus-insect cell expression systems have the capacity to produce many recombinant proteins at high levels and they also provide significant eukaryotic protein processing capabilities.
Direction: A 200 µl of polymerase chain reaction has 100 template DNA molecules and the reaction was performed for 10 cycles.
- How many molecules of amplicons will be generated?
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Let N0 be the initial number of molecules present in the aliquot and let N be the end product of PCR amplification. Let n be the number of cycles performed by the PCR.
We, know N = N0 × 2n for n number of cycles since in each cycle the number of amplicons double the number of parent strands in an exponential manner.
Here, N0 = 100 for a 200 μL solution (given), n = 10
Therefore, N = 100 × 210
= 100 × 1024 = 1.024 × 105
Hence, the required amplicons generated after 10 cycles of PCR run = 1.024 × 105Correct Option: B
Let N0 be the initial number of molecules present in the aliquot and let N be the end product of PCR amplification. Let n be the number of cycles performed by the PCR.
We, know N = N0 × 2n for n number of cycles since in each cycle the number of amplicons double the number of parent strands in an exponential manner.
Here, N0 = 100 for a 200 μL solution (given), n = 10
Therefore, N = 100 × 210
= 100 × 1024 = 1.024 × 105
Hence, the required amplicons generated after 10 cycles of PCR run = 1.024 × 105
- HAT (hypoxanthine, aminopterin and thymidine) is used for selecting the hybridomas based on the following I.Only hybridoma will grow since it inherited the HGPRT genes from B-cells and can synthesize DNA from hypoxanthine. II.Myeloma cells will not grow in cultures since de novo synthesis is blocked by aminopterin and due to the lack of HGPRT enzyme.
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Hybridoma technology is a technology of forming hybrid cell lines (called hybridomas) by fusing a specific antibody-producing B cell with a myeloma (B cell cancer) cell that is selected for its ability to grow in tissue culture and for an absence of antibody chain synthesis. The antibodies produced by the hybridoma are all of a single specificity and are therefore monoclonal antibodies Fused cells are incubated in HAT medium (hypoxanthine-aminopterin-thymidine medium) for roughly 10 to 14 days. Aminopterin blocks the pathway that allows for nucleotide synthesis. Hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack HGPRT. Removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. Unfused B cells die as they have a short life span. In this way, only the B cell-myeloma hybrids survive, since the HGPRT gene coming from the B cells is functional.
Correct Option: C
Hybridoma technology is a technology of forming hybrid cell lines (called hybridomas) by fusing a specific antibody-producing B cell with a myeloma (B cell cancer) cell that is selected for its ability to grow in tissue culture and for an absence of antibody chain synthesis. The antibodies produced by the hybridoma are all of a single specificity and are therefore monoclonal antibodies Fused cells are incubated in HAT medium (hypoxanthine-aminopterin-thymidine medium) for roughly 10 to 14 days. Aminopterin blocks the pathway that allows for nucleotide synthesis. Hence, unfused myeloma cells die, as they cannot produce nucleotides by the de novo or salvage pathways because they lack HGPRT. Removal of the unfused myeloma cells is necessary because they have the potential to outgrow other cells, especially weakly established hybridomas. Unfused B cells die as they have a short life span. In this way, only the B cell-myeloma hybrids survive, since the HGPRT gene coming from the B cells is functional.
- How many molecules of amplicons will be present in 0.1 µl of reaction?
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From previous question, we have
Number of amplicons in 200 μL of the solution after PCR run = 1.024 × 105
Therefore, number of amplicons in 0.1 μL solution = 1.024 × 105 × 0.1 / 200 = 51.2
Hence, the required number of amplicons present in 0.1 μL of the solution = 51.2Correct Option: C
From previous question, we have
Number of amplicons in 200 μL of the solution after PCR run = 1.024 × 105
Therefore, number of amplicons in 0.1 μL solution = 1.024 × 105 × 0.1 / 200 = 51.2
Hence, the required number of amplicons present in 0.1 μL of the solution = 51.2