Biology Exams 4 U

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ABC Model of Flower Development in Arabidopsis thaliana

Flower is considered as a modified shoot. Many genes are involved in the conversion of shoot meristem to floral meristem.
ABC model of floral development explains the genetics behind the formation of different whorls in a flower.
The four whorls are sepal, petal, stamens and carpel.
ABC model whorls
Flower formation is initiated by the activity of genes known as heterochrony or flowering time genes which regulate the conversion of vegetative meristem to floral meristem. Then flower meristem identity genes regulate the formation of flower. Upon initiation of flowering, a third type of genes called cadastral genes will express which govern the whorl formation of the flower. Finally the structure of this whorls and its occurrence at right place is regulated by homeotic genes.
The four whorls are sepal, petal, stamens and carpel.
ABC model was first formulated by George Haughn and Chris Somerville in 1988. Experimental material was Arabidopsis thaliana and Antirrhinum majus.
ABC model predicts that the four whorls of flower are controlled by the action of 3 genes A, B and C in Arabidopsis thaliana. The role of these genes was deduced by inducing mutation in each of these genes.
Key 1: Remember, A and C genes are equally dominant. Mutation of ‘A’ gene makes ‘C’ gene more active.
Key 2: B genes always express in association with A and C.
ABC Model of flower development summary chart
The above figure summarizes the ABC model and changes associated with whorl formation on mutation of A, B and C genes respectively.
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DBT BET JRF Exam 2015 Notification

Biotech Students Don’t miss this exam!
Applications are invited from Indian nationals for the award of “DBT-Junior Research Fellowship” (DBT-JRF) for pursuing research in frontier areas of Biotechnology and Applied Biology.
JRFs will be selected according to merit under two categories: Category I & II.
dbt bet jrf exam
Category I fellowship (Top 275 in number) are tenable in any University/Institute in India where the students can register for Ph.D.
Category II students (100 in number) will be eligible to join any DBT sponsored Project and avail fellowship equivalent to NET/GATE qualifications as per DST Guidelines, subject to selection through institutional selection process. Fellowship will be co-terminus with the duration of project and institutional rules will be applicable. There will be no binding on PIs of DBT sponsored projects to select JRF/SRF for their projects from category II list. Selection in Category II will not entitle student for any fellowship from DBT-JRF program.
For further details please visit https://nccs.digialm.com .
Students can also visit NCCS website for details: www.nccs.res.in/dbtjrf.html
Exam Date: 26 th April, 2015 at 2.30 PM  (Online Test)
Eligibility: Candidates can appear for BET examination only thrice during their career within the prescribed age limit. Candidates who have completed eligibility qualification in a year will be eligible to appear in that year and two subsequent years. Students who have passed after Jan.1, 2013 or will appear this year (till August, 2015) final examination of qualifying degree is eligible. Students with M.Sc. / M.Tech / M.V.Sc. degree with Biotechnology in title of degree e.g. Biotechnology, specialization such as Agricultural, Animal / Veterinary, Medical, Marine, Industrial, Environmental, Pharmaceutical, Food, Bio-resources Biotechnology, “Biochemical Engineering, Bio-sciences and Biotechnology, Bioinformatics” and M.Sc. “Molecular & Human Genetics” and M.Sc. “Neuroscience” as well as B.Tech / B.E. in Biotechnology (4-year course after 10+2) recognized by UGC/AICTE are eligible for this examination.
The applicants should be below the age of 28 years for Open category as on 28th February 2015.
Candidates with minimum 60% for general and OBC category (55% for SC/ST/PH) of the total marks (equivalent grade) are only eligible.
For further details and to apply online please visit the URL https://nccs.digialm.com . Online registration will start on 25 th February 2015 and the last date for submission of online application form is 25 th March, 2015. DBT-BET (category I) entitles a candidate for fellowship subject to Ph.D registration of the candidate in a recognized university or Institute in the country within 2 years. At present, very few institutes or universities allow B.Tech students to register for Ph.D. directly. Registration for Ph.D is candidate’s responsibility and NCCS or DBT have no role in this.
Remember: For lectureship eligibility still you have to qualify NET.
Reservations: Government of India guidelines for reservations will be followed for BET-2015. Age relaxation of 5 years (up to 33 years) for SC /ST/PH and women candidates and 3 years (31 years) for OBC candidates will be given. The age limit will be as on 28th Feb. 2015. SC/ST/PH candidates with 55% of the total marks (equivalent in grade) are eligible to apply.

Fellowship: The fellowship will be initially for a period of 3 years extendable for 2 more years based on performance. By the end of 2nd year, the performance of JRF will be assessed and will be upgraded to SRF. The fellowship for JRF/SRF will be @ Rs. 25,000/- or 28,000/- per month + HRA as per DST guidelines and research contingency of Rs. 30,000/- per year.

Mode of selection: The candidates will be selected based on an online admission test, “Biotechnology Eligibility Test” (BET) to be conducted on 26 th April, 2015 at 2.30 PM in the following twelve cities: New Delhi, Kolkata, Guwahati, Hyderabad, Chennai, Pune, Bangalore, Chandigarh, Lucknow, Patna, Trivandrum & Ahmedabad.

Mode of application: Candidates should register and apply online in the prescribed application form available at the URL https://nccs.digialm.com starting on 25 th February 2015. All the details about the application process and the examination are available on the web site. The last date for submission of online application form is 25 th March, 2015. Stepwise procedure for filling the online application form, payment of application fees and uploading of required documents/certificates is given in the above said URL. General/OBC candidates have to pay an application fee of Rs. 500/- and SC/ST/PH categories are exempted from payment of application fees. The application fees is payable either online or offline as detailed on the web site for completion of application process. The application fee is non-refundable and non-transferable. No TA will be provided to any candidate for attending the examination.
Scanned Copies of following Documents will be required for filling up the application form online
Specification for scanning the documents is available on http://nccs.digialm.com website.
1. Passport size photo
2. Signature
3. Date of birth proof (preferably SSC certificate)
4. Final mark sheet of the qualifying examination showing the cumulative percentage of marks or equivalent CGPA. 5. For students appearing in the final examination in 2015, filled and signed certificate in the format available at http://nccs.digialm.com website.
6. If the candidate belongs to SC/ST/PH/OBC category, they should scan suitable certificate issued by the competent authorities. OBC candidates should produce ‘Non-creamy layer certificate’ for availing the relaxation.
Free DBT-BET-JRF Exam Preparation Resources
First and foremost thing is to begin the preparation now onwards
" Wishing the very Best "
Biology Exams 4 U is preparing with U for your exam. Keep Visiting ………………….
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B cell-T helper cell interaction and associated antibody production: Step wise explanation

Humoral immunity: Pathway 2 B cell as antigen presenting cell (APC)
Definition: Humoral immune response refers to the host defense mechanisms that are mediated by antibodies produced by plasma cells of B cells.
It protects against extracellular bacteria and foreign macromolecules.
There are two pathways in antibody production
Pathway 1: B Cell Mediated Pathway which is independent of T helper cells.
We have already discussed this pathway in the last post.
Pathway 2: B Cell- T helper Cell Mediated Pathway
In this pathway, B cell acts as antigen presenting cell

B cell-T helper cell mediated antibody production
Step 1:
B cell activation=Antigen binding to Naïve B cell receptor.
Antigen degradation inside B cell
B cell possesses B cell receptor or BCR with a single specificity. A naive B cell is the one which hasn't encountered an antigen before. When an epitope of an antigen binds to the B cell receptor, that particular B cell gets activated.
Step 2:
B cell as antigen presenting cells (APCs)
In this pathway, B cells acts as antigen presenting cell that is presenting antigen to T helper cells.
MHC class II receptor is present on all antigen presenting cells like B cells, macrophages, dendritic cells etc.
The antigen is processed inside B cell and is presented on MHC class II to T cell receptor of T helper cell. This MHC class II bound antigenic peptide binds to TCR. T helper cells secrete chemokines or chemical messengers which in turn activates B cells more effectively. T helper cell mediated B cell activation is more effective than independent B cell activation.


Step 3:
Clonal selection and Differentiation:
Division of that activated B cell
This activated B cell is selected to divide forming many copies of that cell. That particular clone of B cell is selected to divide and is called as clonal selection.
Differentiation: Plasma cells and memory B cells
Later this B cells differentiate to form plasma cells or effecter cells and memory B cells
Step 4:
Plasma cells produce antibodies that bind to the antigen and ensure its clearance from the system by agglutination, precipitation or neutralization.
Memory B cells are meant for immunologic memory or secondary immune response. When the same antigen comes for the second time, these memory B cells will recognize it quickly and induce a heightened immune response. This will clear out the pathogen from the system soon.

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Humoral Immune Response: Definition and Summary of Steps involved

Definition: Host defense mechanisms that are mediated by antibodies produced by plasma cells of B cells.
It protects against extracellular bacteria and foreign macromolecules.
Diagram: Steps in Humoral Immune Response
Step 1:
B cell activation=Antigen binding to Naïve B cell receptor
B cell possess B cell receptor or BCR with a single specificity. A naive B cell is the one which hasn't encountered an antigen before. When an epitope of an antigen binds to the B cell receptor, that particular B cell gets activated.
Step 2:
Clonal selection: Division of that activated B cell
This activated B cell is selected to divide forming many copies of that cell. That particular clone of B cell is selected to divide and is called as clonal selection.
Step 3:
Differentiation: Plasma cells and memory B cells
Later this B cells differentiate to form plasma cells or effecter cells and and memory B cells
Step 4:
Plasma cells produce antibodies that binds to the antigen and ensures it clearance from the system.
Memory B cells are meant for immunologic memory or secondary immune response. When the same antigen comes for the second time, these memory B cells will recognize it quickly and induce a heightened immune response. This will clear out the pathogen from the system soon.
There is one more pathway in humoral immune response which is mediated by T helper cells.

For videos
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CSIR UGC NET JRF Life Sciences Exam Notification June 2015. Apply Online Now

CSIR will hold   the Joint CSIR-UGC Test on 21st June, 2015 for determining the eligibility of the Indian National  candidates for the award of Junior Research Fellowships (JRF) and for determining eligibility for appointment of  Lecturers (NET) in certain subject areas falling under the faculty of Science & Technology. The award of Junior Research  Fellowship (JRF) to the successful eligible candidates will depend on their finding admission/placement in a university/  national laboratory/ institution of higher learning and research, as applicable.
CSIR UGC NET exam
Exam Date: CSIR-UGC JRF( Junior Research Fellowship )and NET (Eligibility for Lectureship) : 21st June, 2015.
                                                           Apply Online
Important Dates:
Important dates CSIR UGC life sciences june 2015
Examination Fee
Exam fee deatils CSIR life sciences june2015
Click here for challan
image
Life Science  Exam Scheme
Time: 3 Hours                                                                     MAXIMUM MARKS: 200
CSIR-UGC (NET) Exam for Award of Junior Research Fellowship and Eligibility for Lecturership shall be a Single Paper Test having Multiple Choice Questions (MCQs). The question paper is divided in three parts
Part A:This part shall carry 20 questions pertaining to General Science, Quantitative Reasoning & Analysis and Research Aptitude. The candidates shall be required to answer any 15 questions. Each question shall be of two marks. The total marks allocated to this section shall be 30 out of 200.
Part B: This part shall contain 50 Multiple Choice Questions(MCQs) generally covering the topics given in the syllabus. A candidate shall be required to answer any 35 questions. Each question shall be of two marks. The total marks allocated to this section shall be 70 out of 200.
Part C: This part shall contain 75 questions that are designed to test a candidate's knowledge of scientific concepts and/or application of the scientific concepts. The questions shall be of analytical nature where a candidate is expected to apply the scientific knowledge to arrive at the solution to the given scientific problem. A candidate shall be required to answer any 25 questions. Each question shall be of four marks. The total marks allocated to this section shall be 100 out of 200.

Examination Centres: The test will be held at 26 Centres spread all over India, as specified below: Bangalore, Bhavnagar, Bhopal, Bhubaneshwar, Chandigarh, Chennai, Cochin, Delhi, Guntur, Guwahati, Hyderabad, Imphal, Jammu, Jamshedpur, Karaikudi, Kolkata, Lucknow, Nagpur, Pilani, Pune, Raipur, Roorkee, Srinagar, Thiruvananthapuram, Udaipur and Varanasi.

 Success is the sum of small efforts, repeated day in and day out. So begin your preparation now.
The links given below will definitely help you to reach your dream career in Life Sciences.


Best Wishes from BE4U Team
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Cut off mark or percentage CSIR UGC NET JRF Life Sciences June 2014

This is a reminder. Last time also we posted the same to make you aware the importance of a answering a single question in this exam.
The cutoff percentage for CSIR UGC NET JRF  life sciences for the year 2014 was 51%. I just want to stress the point that whatever you learn, learn deep as each question will take you many miles towards your dream of qualifying this exam. If you are expecting a question from geological time scale, I know you need to remember all those eras and organism groups originated during that time period. Still it is a worth as you got an answer right and you are damn sure about it.
Cut off mark or percentage CSIR UGC NET JRF life science 2014
Your strategy should be "Focus on topics where you can expect questions, in depth preparation will definitely give you the result you want. It is not about the quantity or vastness of the topic you have covered, it is all about your in depth understanding in the topics you covered.
Just sit down, prepare a time table, work out maximum previous question papers and build your confidence.
Success is the sum of small efforts repeated day in and day out. Spent at least 30 minutes a day for your preparation. Definitely, later on you could sit without any distraction for 1 hour or more. Remember all great journeys begins with a single step.
You can.............. just go for it. Jump into the depth of the most beautiful and amazing “science of life”…..

Happy learning and best wishes for the exam....    From Biologyexams4u team
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Different Types of RNA in a Cell

RNA plays many crucial roles inside the cell along with DNA. Basically there are three main types of RNA in a cell.
1. mRNA or messenger RNA that codes for protein
2. rRNA which forms the ribosomes for protein synthesis
3. tRNA as adaptor which binds amino acids and rRNA and translates mRNA to proteins
Different types of RNA in a cell
But many other RNAs has a regulatory role or in processing of pre RNAs
4. snRNA (Small Nuclear RNA): forms snRNPs which is involved in mRNA processing by removing introns.
5. snoRNA (small nucleolar RNA) that forms snRNPs which is involved in maturation and assembly of ribosomal RNAs.
Function of snoRNA: rRNA processing mainly by methylation and pseudourydylation of pre rRNAs during ribosome formation in the nucleolus.
6. siRNA: small interfering RNA involved in RNA interference, a natural phenomenon double stranded RNAs lead to the degradation of mRNA with identical sequences.
siRNA is 21-23 nucleotide double stranded fragments formed for degradation of mRNAs with same sequence during RNA silencing or gene silencing.
Function:
Blocking viral replication and restricting the movement of mobile elements. dsRNA intermediates are involved in both processes.
7. hnRNA: heteronuclear RNA: High molecular weight RNAs (up to 50000 nucleotides), representing many different nucleotide sequences found in the nucleus. Include unprocessed pre mRNA with both introns and exons.
8. Catalytic RNAs or ribozymes: are called as ribozymes. Examples include peptidyl tranferase, spliceosome etc.
Know more on ribozymes
9. Telomerase RNA: RNA molecule that acts as a template for the addition of nucleotides to the 3’ end of the duplicating strand thus avoiding end replication problem.
10. gRNA: It is guide RNA needed for RNA editing, in removal and insertion of bases into mRNA, reported in some protists.
11. tmRNA: Transfer-messenger RNA (abbreviated tmRNA, also known as 10Sa RNA) is a bacterial RNA molecule with dual tRNA-like and messenger RNA-like properties.
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Cell Theory and Modern Cell Theory

Robert Hooke was the first to describe cell and he published his observation in his book Micrographia (1670). He sliced a piece of cork and placed under his microscope. He observed honey comb like structural units and called it as the “cell”.
Robert Hooke
Leeuwenhoek (1674) was the first one to observe live cells under microscope. He observed many things including bacteria under his primitive microscope and drew beautiful sketches of his observations.
If you want to see this classical book, follow this link http://archive.nlm.nih.gov/proj/ttp/flash/hooke/hooke.html
Cell theory was actually a generalization of observations made by many scientists around the world.
Cell theory was proposed by Theodor Schwann, Matthias Schleiden and Rudolf Virchow
cell theory
The three tenets are
1. All living organisms are composed of one or more cells (Schwann and Schleiden, 1838-39).

2. The cell is the basic structural and functional unit of life (Schwann and Schleiden, 1838-39).
Schleiden proposed that new cells arise from within the old cells, specifically from the nucleus. This was corrected by Rudolf Virchow who proposed “Theory of cell lineage” stating that “omnis cellulae e cellula” (all cells arise from pre-existing cells).

3. All cells arise from pre existing cells by cell division (Rudolf Virchow, 1858).

Modern cell theory
Some more points are added with the advancement of our knowledge in cytology and molecular biology.
• The cell contains hereditary information DNA which is passed on from cell to cell during cell division
• All cells are basically the same in chemical composition and metabolic activities
• All basic chemical and physiological functions are carried out inside the cells (digestion, movement etc)
• A cells activity depends on the activities of sub cellular structures within the cell (organelles, plasma membrane etc)

Learn more:
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