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Did the first cell self-replicate or was it multiple first cells?

Did the first cell self-replicate or was it multiple first cells?


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We're almost sure by now that the first cell was born in a some kind of underwater vents environment which harvested all the necessary conditions for it to exist.

However, did the first cell self-replicate to have other cells or did the same process lead to the birth of others as well? If the latter is true, doesn't this make the evolution of cells more common once the primitive conditions exist?


Good question. Simple answer here: we have absolutely no idea.

I would hazard a guess to say that the first proto-cell probably did not have the ability to replicate, so there must have been many proto-cells prior to the occurrence of the first true cell with the property to replicate itself with some degree of fidelity. Whether or not at some point cells existed that could be traced to two or more independent abiotic generations, that is unknown. The likelihood of this event is all we can talk about. I defer to biochemists working on this (still very open) problem, but I think it is honest to mention that they too have no idea, really. This is because, as we can surely appreciate, likelihood and outcome are two entirely different things. And unlikely events happen all the time. Each life form and individual is astonishingly unlikely, but historical contingency so happens to have brought us all here despite the odds.


Activation of multiple receptors stimulates extracellular vesicle release from trophoblast cells

Reports of the stimulated release of extracellular vesicles (EVs) are few, and the mechanisms incompletely understood. To our knowledge, the possibility that the activation of any one of the multitudes of G-protein-coupled receptors (GPCRs) expressed by a single cell-type might increase EV release has not been explored. Recently, we identified the expression of cholecystokinin (CCK), gastrin, gastrin/cholecystokinin types A and/or B receptors (CCKAR and/or -BR), and the bitter taste receptor, TAS2R14 in the human and mouse placenta. specifically, trophoblast. These GPCR(s) were also expressed in four different human trophoblast cell lines. The current objective was to employ two of these cell lines-JAR choriocarcinoma cells and HTR-8/SVneo cells derived from first-trimester human villous trophoblast-to investigate whether CCK, TAS2R14 agonists, and other GPCR ligands would each augment EV release. EVs were isolated from the cell-culture medium by filtration and ultracentrifugation. The preparations were enriched in small EVs (<200 nm) as determined by syntenin western blot before and after sucrose gradient purification, phycoerythrin (PE)-ADAM10 antibody labeling, and electron microscopy. Activation of TAS2R14, CCKBR, cholinergic muscarinic 1 & 3, and angiotensin II receptors, each increased EV release by 4.91-, 2.79-, 1.87-, and 3.11-fold, respectively (all p < .05 versus vehicle controls), without significantly changing EV diameter. A progressive increase of EV concentration in conditioned medium was observed over 24 hr consistent with the release of preformed EVs and de novo biogenesis. Compared to receptor-mediated stimulation, EV release by the calcium ionophore, A23187, was less robust (1.63-fold, p = .08). Diphenhydramine, a TAS2R14 agonist, enhanced EV release in JAR cells at a concentration 10-fold below that required to increase intracellular calcium. CCK activation of HTR-8/SVneo cells, which did not raise intracellular calcium, increased EV release by 2.06-fold (p < .05). Taken together, these results suggested that other signaling pathways may underlie receptor-stimulated EV release besides, or in addition to, calcium. To our knowledge, the finding that the activation of multiple GPCRs can stimulate EV release from a single cell-type is unprecedented and engenders a novel thesis that each receptor may orchestrate intercellular communication through the release of EVs containing a subset of unique cargo, thus mobilizing a specific integrated physiological response by a network of neighboring and distant cells.

Keywords: GPCR angiotensin bitter taste receptor calcium cholecystokinin exosome muscarinic receptor placenta.

© 2020 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Conflict of interest statement

No conflicts of interest, financial or otherwise, are declared by the authors.


The Embryo Project Encyclopedia

"On the Origin of Mitosing Cells" by Lynn Sagan appeared in the March 1967 edition of the Journal of Theoretical Biology. At the time the article was published, Lynn Sagan had divorced astronomer Carl Sagan, but kept his last name. Later, she remarried and changed her name to Lynn Margulis, and will be referred to as such throughout this article. In her 1967 article, Margulis develops a theory for the origin of complex cells that have enclosed nuclei, called eukaryotic cells. She proposes that three organelles: mitochondria, plastids, and basal bodies, which are all parts of eukaryotic cells, were once free-living cells that took residence inside primitive eukaryotic cells. This process Margulis called endosymbiosis. Margulis' theory explained the origin of eukaryote cells, which are the fundamental cell type of most multicellular organisms and form the basis of embryogenesis. After fertilization, embryos develop from a single eukaryotic cell that divides by mitosis.

When the Journal of Theoretical Biology published her article in 1967, Margulis was a professor at Boston University in Boston, Massachusetts. Margulis independently proposed ideas similar to those proposed by biologists in the late nineteenth and early twentieth centuries. At the end of the nineteenth century, several researchers advanced theories similar to symbiosis, two of whom were Richard Altmann of Leipzig, Germany, and Peter Kropotkin who was exiled from Russia and living in England. At the beginning of the twentieth century, researchers such as Boris Kozo-Polyansky in Russia and Ivan Wallin, a professor at the University of Colorado in Boulder, Colorado, also proposed theories similar to that of endosymbiosis.

These earlier biologists theorized that the energy-producing mitochondria, and the photosynthesizing plastids of algae and plants, resulted from a symbiotic relationship between different types of free-living cells. In addition, several of the researchers also hypothesized that the sub-cellular organelles contained hereditary information similar to that found in the nucleus. However, when earlier biologists put forth theories of symbiosis, they lacked the technological resources to test them. By the time Margulis proposed her theory, evidence for symbiosis theories was available from microscope studies of cells, electron microscopy, genetics, and molecular biology. Such evidence enabled Margulis to support her theories with experimental data.

"On the Origin of Mitosing Cells" has four main sections: an "Introduction," followed by sections titled, "Hypothetical Origin of Eukaryotic Cells," in which Margulis presents a theory for the origin of eukaryotic cells "Evidence from the Literature," in which she reviews the literature that supports the sequence of the origin of eukaryotic cells and "Some Predictions," in which she presents experimental evidence that support predictions made based on her theory.

In the "Introduction," Margulis states that all free-living organisms are made of cells. She describes differences between eukaryotic cells, which have distinct nuclei, and prokaryotic cells, which lack distinct nuclei. Researchers didn't note those differences until the 1960s, shortly before Margulis published her paper. Margulis focuses on three sub-cellular organelles of eukaryotic cells, the mitochondria, chloroplasts, and (9+2) basal bodies, which she asserts were once free-living prokaryotic cells. (9+2) basal bodies are organelles found at the base of eukaryotic whip-like structures, such as the flagellum of sperm cells.

Margulis begins her argument with a section titled, "Hypothetical Origin of Eukaryotic Cells," which has multiple subsections. She describes the state of prokaryotic cells of two billion years ago, before the accumulation of free oxygen in the atmosphere. At that time, prokaryotic cells contained DNA, they synthesized proteins on structures made of RNA, called ribosomes, and they used messenger RNA (mRNA) to help build those proteins from DNA. With oxygen accumulating in the atmosphere, prokaryotic cells developed nucleotide sequences, or genes, that coded for molecules that could bind with metals and oxygen, called porphyrins. This mutation provided a protective advantage from the harmful effects of oxidization. Margulis explained that these cells evolved to contain mechanisms that used oxygen to produce the molecule that stores energy in cells, adenosine-5'-triphosphate (ATP), and other nucleotides that used solar energy, which the chlorophyll-like porphyrins absorbed and used to produce complex sugars. In contrast, more primitive cells, called heterotrophs, fermented ATP from simple sugars. Additionally, some porphyrins used oxygen to release and to store ATP in the absence of light, a process called aerobic respiration.

Next, Margulis discusses how eukaryotic cells evolved from prokaryotic cells via endosymbiosis. Margulis suggests the emergence of eukaryotes was a response to the new oxygen-containing atmosphere. From geological evidence, oxygen became present in the atmosphere as early as 2.7 billion years ago, however the atmosphere became oxygen rich 1.2 billion years ago. Margulis argues that to survive and reproduce, cells had to adapt to the oxygen rich environment or find a specialized environment lacking oxygen. She suggests the eukaryotes originated when an anaerobic heterotroph living on organic matter ingested an aerobic microbe. The ingested microbe became obligate and resulted in, as Margulis calls it, the first aerobic amoeboid organism. Margulis hypothesizes that some of these amoeboid organisms ingested motile prokaryotes (flagellates) that became symbiotic with their host, and thus classical mitosis evolved. Mitosis is a process by which a non-reproductive cell divides into two genetically identical cells, thus passing all of its genetic information to the two daughter cells.

Margulis next discusses the evolution of mitosis in protists and hypothesizes that a motile spiral shaped bacteria was one of the prokaryotes ingested by the large amoeboids, and that the amoeboids became hosts to the motile parasites. Amoeboids benefited from this endosybmiont relationship, as the motility of the parasite gave the host the ability to pursue food before mitosis evolved. Margulis then proposes that the endosymbiont genes, which give rise to the (9+2) substructure, evolved over generations to form chromosomal centromeres, the structures that link together the individual chromatids from duplicated chromosomes. She also claims that the endosymbiotic genes contributed to the small centrioles that facilitate cell mitosis in animals. Margulis hypothesized that the motile prokaryote parasite was the ancestor of the flagellum found in later eukaryotic cells.

Margulis two further topics in the first section of her paper. First, she recreates the steps in evolution of the centromeres, centrioles, and the (9+2) flagella basal bodies from steps for which she had found support in other publications. Then she discusses the evolution of eukaryotic plants, a process she attributes to symbiotic relationships between protozoans and prokaryotic algae. Margulis asserts that the process of mitosis took millions of years to evolve, and she claims that the process evolved millions of years after the evolution of photosynthesis. Margulis then argues that her hypothesis on the origin of eukaryotes is inconsistent with the theory that eukaryotic plant cells first evolved photosynthesis, which eliminates oxygen from plants, and then structured that process into membrane-bound plastids. Instead, Margulis proposes that plants acquired photosynthetic plastids through multiple symbiotic relationships that occurred over time, each of which led to endosymbiosis.

In the next section of her paper, "Evidence from the Literature," Margulis supports her theory by discussing publications on the subject up through 1967. Margulis considers the claim that the more traits two organisms share, the more closely related those organisms are. She says that the hypothesis holds for some organisms, but not for single celled microbes. Margulis acknowledges that she had inadequate data to support that claim, but she contends that the recent studies in molecular biology confirm her theory. Margulis then proposes to use methods from molecular biology to address issues in taxonomy. She next proposes that photosynthesis evolved separately in several diverse organisms. Then, Margulis reviews the general properties of symbiosis, and she says that the origin of eukaryotic cells indicates that larger cells acquired mitochondria, the genome of the (9+2) complex flagellum, and the photosynthetic plastids by endosymbiosis.

Margulis reports that the literature lists six general criteria for organelles derived by endosymbiosis. She applies these criteria to the three organelles, mitochondria, plastids, and the basal bodies, and she concludes that they could have evolved by endosymbiosis, but that the eukaryotic cell nucleus could not have. In the remaining sections of her literature review, Margulis concentrates on the origin of the prokaryotic cells, which she argues evolved into the organelles of eukaryotic cells. Margulis describes the evolution of photosynthesis in cells, the accumulation of oxygen in the atmosphere, and the evolution of aerobic cells. She then discusses research on how mitochondria self-replicate, and she includes a table with a list of mechanisms by which eukaryotic cells, throughout mitosis and their life cycles, retain mitochondria and chloroplasts.

Margulis concludes with the third and final section of the paper, "Some Predictions." She suggests that some of the classifications presented in the phylogenetic tree put forth by previous scientists were likely in error. But if her hypothesis about the origination of the three organelles is correct, so too should be her classification of all eukaryotes. However, Margulis predicts that if these three organelles—mitochondria, plastids, and basal bodies—did originate as free-living microbes, then new technologies would provide researchers the tools required to grow those organelles in vitro. Mitochondria and chloroplasts cannot grow outside of cells, because they have lost too many genes to be free living again. Margulis concludes that all eukaryotic cells must be regarded as multi-genome systems. She says that the evolution of mitosis in primitive eukaryotic cells enabled genes to pass independently from one generation to the next.

Margulis submitted "On the Origin of Mitosing Cells" to at least fifteen journals before it was accepted and published in June 1967. She later expanded on the theory of endosymbiosis in a book titled, Origin of Eukaryotic Cells, published in 1970. In 1981, Margulis published a revised edition titled, Symbiosis in Cell Evolution, which included molecular data to support her findings. In 1993 she published another edition of Symbiosis in Cell Evolution claiming that the difference between prokaryotes and eukaryotes is the most significant division in biology.

By the 1990s, Margulis' theory on the origin of eukaryotes had influenced many scientists. In 2011, John M. Archibald, a professor and researcher at Dalhousie University, in Nova Scotia, Canada, said that Margulis' Origin of Eukaryotic Cells influenced scientists to accept the process of endosymbiosis in the evolution of cells.


Notable Achievements Using HeLa Cells

HeLa cells have been used to test the effects of radiation, cosmetics, toxins, and other chemicals on human cells. They have been instrumental in gene mapping and studying human diseases, especially cancer. However, the most significant application of HeLa cells may have been in the development of the first polio vaccine. HeLa cells were used to maintain a culture of polio virus in human cells. In 1952, Jonas Salk tested his polio vaccine on these cells and used them to mass-produce it.


Stratum Granulosum

The stratum granulosum has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum. The cells (three to five layers deep) become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin, which is fibrous, and keratohyalin, which accumulates as lamellar granules within the cells (see Figure 3). These two proteins make up the bulk of the keratinocyte mass in the stratum granulosum and give the layer its grainy appearance. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that will form the stratum lucidum, the stratum corneum, and the accessory structures of hair and nails.


The Origins of Cell Theory

Figure 1. Robert Hooke (1635–1703) was the first to describe cells based upon his microscopic observations of cork. This illustration was published in his work Micrographia.

The English scientist Robert Hooke first used the term “cells” in 1665 to describe the small chambers within cork that he observed under a microscope of his own design. To Hooke, thin sections of cork resembled “Honey-comb,” or “small Boxes or Bladders of Air.” He noted that each “Cavern, Bubble, or Cell” was distinct from the others (Figure 1). At the time, Hooke was not aware that the cork cells were long dead and, therefore, lacked the internal structures found within living cells.

Despite Hooke’s early description of cells, their significance as the fundamental unit of life was not yet recognized. Nearly 200 years later, in 1838, Matthias Schleiden (1804–1881), a German botanist who made extensive microscopic observations of plant tissues, described them as being composed of cells. Visualizing plant cells was relatively easy because plant cells are clearly separated by their thick cell walls. Schleiden believed that cells formed through crystallization, rather than cell division.

Theodor Schwann (1810–1882), a noted German physiologist, made similar microscopic observations of animal tissue. In 1839, after a conversation with Schleiden, Schwann realized that similarities existed between plant and animal tissues. This laid the foundation for the idea that cells are the fundamental components of plants and animals.

In the 1850s, two Polish scientists living in Germany pushed this idea further, culminating in what we recognize today as the modern cell theory. In 1852, Robert Remak (1815–1865), a prominent neurologist and embryologist, published convincing evidence that cells are derived from other cells as a result of cell division. However, this idea was questioned by many in the scientific community. Three years later, Rudolf Virchow (1821–1902), a well-respected pathologist, published an editorial essay entitled “Cellular Pathology,” which popularized the concept of cell theory using the Latin phrase omnis cellula a cellula (“all cells arise from cells”), which is essentially the second tenet of modern cell theory. [1] Given the similarity of Virchow’s work to Remak’s, there is some controversy as to which scientist should receive credit for articulating cell theory. See the following Eye on Ethics feature for more about this controversy.

Science and Plagiarism

Rudolf Virchow, a prominent, Polish-born, German scientist, is often remembered as the “Father of Pathology.” Well known for innovative approaches, he was one of the first to determine the causes of various diseases by examining their effects on tissues and organs. He was also among the first to use animals in his research and, as a result of his work, he was the first to name numerous diseases and created many other medical terms. Over the course of his career, he published more than 2,000 papers and headed various important medical facilities, including the Charité – Universitätsmedizin Berlin, a prominent Berlin hospital and medical school. But he is, perhaps, best remembered for his 1855 editorial essay titled “Cellular Pathology,” published in Archiv für Pathologische Anatomie und Physiologie, a journal that Virchow himself cofounded and still exists today.

Despite his significant scientific legacy, there is some controversy regarding this essay, in which Virchow proposed the central tenet of modern cell theory—that all cells arise from other cells. Robert Remak, a former colleague who worked in the same laboratory as Virchow at the University of Berlin, had published the same idea 3 years before. Though it appears Virchow was familiar with Remak’s work, he neglected to credit Remak’s ideas in his essay. When Remak wrote a letter to Virchow pointing out similarities between Virchow’s ideas and his own, Virchow was dismissive. In 1858, in the preface to one of his books, Virchow wrote that his 1855 publication was just an editorial piece, not a scientific paper, and thus there was no need to cite Remak’s work.

By today’s standards, Virchow’s editorial piece would certainly be considered an act of plagiarism, since he presented Remak’s ideas as his own. However, in the nineteenth century, standards for academic integrity were much less clear. Virchow’s strong reputation, coupled with the fact that Remak was a Jew in a somewhat anti-Semitic political climate, shielded him from any significant repercussions. Today, the process of peer review and the ease of access to the scientific literature help discourage plagiarism. Although scientists are still motivated to publish original ideas that advance scientific knowledge, those who would consider plagiarizing are well aware of the serious consequences.

In academia, plagiarism represents the theft of both individual thought and research—an offense that can destroy reputations and end careers. [2] [3] [4] [5]

Figure 2. (a) Rudolf Virchow (1821–1902) popularized the cell theory in an 1855 essay entitled “Cellular Pathology.” (b) The idea that all cells originate from other cells was first published in 1852 by his contemporary and former colleague Robert Remak (1815–1865).

Think about It

  • What are the key points of the cell theory?
  • What contributions did Rudolf Virchow and Robert Remak make to the development of the cell theory?

Maternal Effect Genes in Development

Sarah E. Cabral , Kimberly L. Mowry , in Current Topics in Developmental Biology , 2020

7.1 Nucleoli

Nucleoli are subdomains of the nucleus dedicated to ribosome biogenesis and, as mentioned previously, were the first membraneless compartment observed in the cell (reviewed in Pederson, 2011 ). Using the thermodynamic principles of liquid-liquid phase separation and the enormous nuclei of the stage V Xenopus oocyte (

0.4–0.5 mm), researchers quickly characterized the nucleolus as a biomolecular condensate with liquid-like properties ( Brangwynne et al., 2011 ). Nucleoli contain subcompartments important for different stages of ribosome production, but until recently the mechanisms of subdomain formation were unclear (reviewed in Thiry & Lafontaine, 2005 ). Interestingly, the subcompartments of the nucleolus were found to be co-existing, immiscible liquid phases within the larger biomolecular condensate, with differential biophysical properties and primary surface tension driving organization of the subcompartments ( Feric et al., 2016 ). The large size of Xenopus oocyte nucleoli has made them the ideal model to study additional questions in phase separation, such as the role of ATP in phase separation and the role of transcription within condensates ( Berry et al., 2015 Hayes, Peuchen, Dovichi, & Weeks, 2018 ).


2 Mark Questions

Chapter 11
Biotechnology Principles and Processes

2 Marks Questions
1.Name two main steps which are collectively referred to as down streaming process. Why is this process significant?
Ans. Separation and Purification
This process is essential because before reaching into market, the product has to be subjected for clinical trial and quality control.

2. How does plasmid differ from chromosomal DNA?
Ans.

Plasmid DNA Chromosomal DNA
(i)
(ii)
(iii)
Circular DNA
Occurs only in bacterial cells
Used as Vector
in rDNA technology
(i)
(ii)
(iii)
Linear DNA
Occurs in nucleus of eukaryotic cells
and bacterial cell.
Not used as vector in rDNA
technology.

3. A bacterial cell is shown in the figure given below. Label the part ‘A’ and ‘B’. Also mention the use of part ‘A’ in rDNA technology.

Ans. A- Plasmid, B – Nucleoid
Plasmid is used as vector to transfer the gene of interest in the host cell.

4. Mention two classes of restriction enzymes. Suggest their respective roles.
Ans .Exonucleases and endonucleases

  • Exonucleases remove nucleotides from the ends of the DNA.
  • Endonucleases cut DNA at specific sites beween the ends of DNA.

5. In the given process of separation and isolation of DNA fragments, someof the steps are missing, Complete the missing steps –
A : Digestion of DNA fragments using restriction endonucleases

B : ……………………………………………………..

C : Staining with ethidium bromide

D :Visualisation in U.V. light

E : …………………………………………………….

F : Purification of DNA fragments.
Ans .B – Gel Electrophoresis
E – Elution

6.Write any two properties of restriction endonuclease enzymes?
Ans .(i) Each Restriction endonuclease functions by inspecting the length of DNA sequence & bindto DNA at the recognition Sequence.
(ii) It cuts the two strands of DNA at specific point in their sugar – phosphate backbone.

7.What are ‘Selectable marker’? What is their use in genetic engineering?
Ans .A selectable marker is a gene which helps in selecting those host cells which contains thevector& eliminating the non–transformanteg – gene encoding resistance to antibiotics are usefulSelectable markers as they allow Selective growth of transformants only.

8.How can the desired product formed after genetic engineering be produced on a commercial scale?
Ans. The product obtained from genetic engineering is subjected to a series of processes collectivelycalled downstream processing before it made into final processes involved in downstreamprocessing are :- Separation & purification.

9.What is “Insertional Inactivation”?
Ans .If a recombinant DNA is inserted within the coding Sequence of enzyme B–galactosidase. Thisresults into inactivation of enzyme which is referred to as “Insertional Inactivation”. The presenceof chromogenic Substrate gives blue–coloured colonies if the plasmid in bacteria does not have aninsert presence of insert results into insertional inactivation &the colonies do not produce anycolor.

10.What are the two basic techniques involved in modern Biotechnology?
Ans. The two basic techniques involved in modern Biotechnology are:-
a)Genetic Engineering is the technique of altering the nature of genetic material or introduction of it into another host organism to change its phenotype.
b)Techniques to facilitate the growth & multiplication of only the desired microbes or cells in large number under sterile conditions for manufacture

11.Represent diagrammatically the E. coli. Cloning vector β β PBR 322.
Ans .

12.Differentiate between plasmid DNA and chromosomal DNA?
Ans. Plasmid DNA is extranuclear DNA, found in protoplasmic whereas chromosomal DNA is the nuclear or genetic DNA which is found within the nucleus.

13.What is the role of enzyme “Ligase” in genetic Engineering?
Ans .Enzyme “Ligase” acts as molecular Suture which helps in joining two pieces of DNA. The Joining process requires ATP as it derive energy to construct phosphodiester bond between cohesive ends.

14.Name the components a bioreactor must possess to achieve the desired product?
Ans .Enzyme “Ligase” acts as molecular Suture which helps in joining two pieces of DNA. The Joining process requires ATP as it derive energy to construct phosphodiester bond between cohesive ends.

15.The following proteins of given molecular weight are Subjected to Get electrophoresis. Write the order of Sequence in which these proteins are isolated in a gel?

S.no.ProteinsMol.wt
1.Albumin23,000
2.Keratin48,000
3.Myosin1,25,000
4.Haemoglobin84,000
5.Ribozyme62,000
6.Insulin1,14,000

Ans .The sequence of proteins obtained from top to bottom in a gel:-
Myosin > Insulin >Haemoglobin> Ribozyme > Keratin > Albumin.

16.How is gene Z used as a marker?
Ans .Lac Z gene codes for enzyme Β-galactosidase, if a recombinant DNA is inserted within thecoding sequence of an enzyme Β-galactosidase. This results into inactivation of enzyme. Thebacterial colonies whose plasmid does not have an insert produce blue colour but those with aninsert do not produce any colour.

17.What is Bioreactor? What are the advantages of Stirred tank Bioreactor over Shake flask. Show diagrammatically a simple Stirred tank Bioreactor?
Ans .Bioreactors are large vessels in which raw materials are biologically converted into specificproteins using microbial, plant, animal or human cells. The advantages of Bioreactor over shakeflask are :-
a)It provides optimal conditions for achieving desired product by providing optimum growth conditions eg. temp, pH etc.
b)Small volume of cultures can be withdrawn periodically from bioreactor to test the sample.
c)It has an agitation system, temp control system, from control system & pH control system
d)


Biotechnology: Principles and Processes Class 12 MCQs Questions with Answers

Multiple Choice Type Questions

Question 1.
Micro-organisms can be grown in the bioreactors by
(a) Support growth system
(b) Agitated growth system
(c) Suspended .growth system
(d) Both (a) and (c)

Question 2.
Name the drug used in cancer treatment produced by using biotechnology
(a) Terramycin
(b) HGH
(c) Insulin
(d) TSH
(e) Enterferon

Question 3.
During ‘gene cloning’ which is called as ‘gene taxi’?
(a) Vaccine
(b) Plasmid
(c) Bacterium
(d) Protozoa

Question 4.
Hybridoma technology has been successfully used in
(a) production of somatic hybrids
(b) synthesis of monoclonal antibodies
(c) synthesis of haemoglobin
(d) production of alcohol in bulk

Answer: (b) synthesis of monoclonal antibodies

Question 5.
Introduction of food plants developed by genetic engineering is not desirable because
(a) These products are less tasty as compared to the already existing products
(b) The method is costly
(c) Economy of developing countries may suffer.
(d) There is danger of entry of viruses and toxins with introduced crop

Answer: (a) These products are less tasty as compared to the already existing products

Question 6.
Hybridoma cells are
(a) Nervous cells of frog
(b) Hybrid cells resulting from myeloma cells
(c) Only cells having oncogenes
(d) Product of spore formation in bacteria

Answer: (b) Hybrid cells resulting from myeloma cells

Question 7.
The new strain of bacteria produced by biotechnology in alcohol industry is
(a) Escherichia coli
(b) Saccharomyces cerevisiae
(c) Bacillus sabtilis
(d) Pseudomonas putida

Answer: (d) Pseudomonas putida

Question 8.
Important objective of biotechnology in agriculture section is
(a) To produce pest resistant varieties of plants
(b) To increase the nitrogen content
(c) To decrease the seed number
(d) To increase the plant weight

Answer: (a) To produce pest resistant varieties of plants

Question 9.
The two vitamins manufactured biotechnologically are
(a) Vitamin B12 and Vitamin B6
(b) Vitamin B12 and Vitamin B2
(c) Vitamin B6 and Vitamin B2
(d) Vitamin B12 and Vitamin B9

Answer: (b) Vitamin B12 and Vitamin B2

Question 10.
Some pathogenic bacteria develop resistance to antibiotics by
(a) Modifying their cell walls
(b) Developing such enzymes which modify antibiotics
(c) Alter the antibiotics target due to spontaneous mutation
(d) All the above.

Question 11.
What was the world’s first ever mammal to be successfully cloned from an adult cell?
(a) Sheep
(b) Monkey
(c) Cow
(d) Calf

Question 12.
Which of the following organelles is associated with genetic , engineering?
(a) Plasmids
(b) Plastids
(c) Chloroplast
(d) Mitochondria

Question 13.
What is cDNA?
(a) Circular DNA
(b) Cloned DNA
(c) DNA produced from reverse transcription of RNA
(d) Cytoplasmic DNA

Answer: (c) DNA produced from reverse transcription of RNA

Question 14.
The EcoR-1 enzyme is obtained from
(a) Virus
(b) Salmonella
(c) E.Coli
(d) Penicillium

Question 15.
The first artificial plant hybrid was made around 1717 by
(a) Thomas Fair child
(b) De Vries
(c) Borlaug
(d) None of these

Answer: (a) Thomas Fair child

Question 16.
Gene was synthesized in vitro by
(a) Khorana
(b) Ochoa
(c) Hollay
(d) Nirenberg

Question 1.
Single cell protein (SCP) provides a valuable rich supplement in ………………. diet.

Answer: Agrobacterium tumefaciens

Question 3.
Fruit softening in tomato is promoted by the enzyme ………………. which degrades pectin.

Question 4.
Vaccine for ………………. has been recently produced through genetic engineering.

Question 5.
Genetically produced human insulin is named ……………….

Answer: Waksman and Woodruff

Answer: cereals, vegetables and yeast

Question 1.
The origin of replication is responsible for initiating replication of the chromosome.

Question 2.
Endonucleases made a cut at the end of the DNA strand.

Question 3.
Ethidium bromide is a staining agent in electrophoresis.

Question 4.
Plasmids are present in single number in a bacterial cell.

Question 5.
Chloramphenicol is used as a marker in selecting trans-formats in genetic engineering.

Question 6.
DNA is a hydrophobic molecule.

Question 7.
Microinjection is used to ligate DNA fragments.

Question 8.
Gene gun is used to inject DNA into host cells.

Question 9.
Chitinase are used to dissolve cell wall of fungus.

Question 10.
Phenol extraction is used to purify a DNA sample.

Question 1.
What are organic compounds produced by a micro-organism that inhibits the growth of or kill another micro-organism called?

Question 2.
Which enzyme is most commonly used for the crop- improvement in genetic engineering?

Answer: Restriction endonucleases.

Question 3.
What does EFB stands for?

Answer: European Federation of Biotechnology.

Question 4.
To produce multiple copies of a gene which technique is used?

Answer: PCR : Polymerase Chain Reaction.

Question 5.
What are molecular scissors?

Answer: Restriction enzymes.

Question 6.
Who made the first recombinant DNA?

Answer: 1972, Stanley Cohen and Herbert Boyer.

Question 7.
Name the specific base sequence where restriction enzymes cut

Answer: Recognition sequence.

Question 8.
Name the DNA sequence of base pairs that reads the same on two strands if the orientation is kept same.

Question 9.
In an agarose gel electrophoresis DNA will move in which direction?

Answer: Towards anode (positive electrode).

Question 10.
How large productions of bio-chemical compounds is done?

Column I Column II
1. Ti-plasmid A. Component of bacterial chromosome
2. Bacteriophages B. Retroviruses
3. Single circular DNA molecule C. Agrobacterium
4. Viruses capable of reverse transcription D. Protein coat of viruses
5. Capsid E. Viruses infecting bacteria
Answer

Column I Column II
1. Ti-plasmid C. Agrobacterium
2. Bacteriophages E. Viruses infecting bacteria
3. Single circular DNA molecule A. Component of bacterial chromosome
4. Viruses capable of reverse transcription B. Retroviruses
5. Capsid D. Protein coat of viruses

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Stem cell timeline: The history of a medical sensation

Stem cells are the cellular putty from which all tissues of the body are made. Ever since human embryonic stem cells were first grown in the lab, researchers have dreamed of using them to repair damaged tissue or create new organs, but such medical uses have also attracted controversy. Yesterday, the potential of stem cells to revolutionise medicine got a huge boost with news of an ultra-versatile kind of stem cell from adult mouse cells using a remarkably simple method. This timeline takes you through the ups and downs of the stem cell rollercoaster.

1981, Mouse beginnings
Martin Evans of Cardiff University, UK, then at the University of Cambridge, is first to identify embryonic stem cells – in mice.

1997, Dolly the sheep
Ian Wilmut and his colleagues at the Roslin Institute, Edinburgh unveil Dolly the sheep, the first artificial animal clone. The process involves fusing a sheep egg with an udder cell and implanting the resulting hybrids into a surrogate mother sheep. Researchers speculate that similar hybrids made by fusing human embryonic stem cells with adult cells from a particular person could be used to create genetically matched tissue and organs.

1998, Stem cells go human
James Thomson of the University of Wisconsin in Madison and John Gearhart of Johns Hopkins University in Baltimore, respectively, isolate human embryonic stem cells and grow them in the lab.

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2001, Bush controversy
US president George W. Bush limits federal funding of research on human embryonic stem cells because a human embryo is destroyed in the process. But Bush does allow continued research on human embryonic stem cells lines that were created before the restrictions were announced.

2005, Fraudulent clones
Woo Suk Hwang of Seoul National University in South Korea reports that his team has used therapeutic cloning – a technique inspired by the one used to create Dolly – to create human embryonic stem cells genetically matched to specific people. Later that year, his claims turn out to be false.

2006, Cells reprogrammed
Shinya Yamanaka of Kyoto University in Japan reveals a way of making embryonic-like cells from adult cells – avoiding the need to destroy an embryo. His team reprograms ordinary adult cells by inserting four key genes – forming “induced pluripotent stem cells”.

2007, Nobel prize
Evans shares the Nobel prize for medicine with Mario Capecchi and Oliver Smithies for work on genetics and embryonic stem cells.

2010, Spinal injury
A person with spinal injury becomes the first to receive a medical treatment derived from human embryonic stem cells as part of a trial by Geron of Menlo Park, California, a pioneering company for human embryonic stem cell therapies.

2012, Blindness treated
Human embryonic stem cells show medical promise in a treatment that eases blindness.

2012, Another Nobel
Yamanaka wins a Nobel prize for creating induced pluripotent stem cells, which he shares with John Gurdon of the University of Cambridge.

2013, Therapeutic cloning
Shoukhrat Mitalipov at the Oregon National Primate Research Center in Beaverton and his colleagues produce human embryonic stem cells from fetal cells using therapeutic cloning – the breakthrough falsely claimed in 2005.

2014, Pre-embryonic state
Charles Vacanti of Harvard Medical School together with Haruko Obokata at the Riken Center for Developmental Biology in Kobe, Japan, and colleagues announced a revolutionary discovery that any cell can potentially be rewound to a pre-embryonic state – using a simple, 30-minute technique.

2014, Therapeutic cloning – with adult cells
Teams led by Dieter Egli of the New York Stem Cell Foundation and Young Gie Chung from CHA University in Seoul, South Korea, independently produce human embryonic stem cells from adult cells, using therapeutic cloning. Egli’s team use skin cells from a woman with diabetes and demonstrate that the resulting stem cells can be turned into insulin-producing beta cells. In theory, the cells could be used to replace those lost to the disease.

2014, Human trials
Masayo Takahashi at the same Riken centre is due to select patients for what promises to be the world’s first trial of a therapy based on induced pluripotent stem cells, to treat a form of age-related blindness.


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