Biology Exams 4 U

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Summary of Fluid Mosaic Model of Plasma Membrane by Singer and Nicolson 1972

Proposed by S J Singer and Garth L Nicolson
Published in the journal “Science’’ in 1972.
Composition: Cell membrane is made up of lipid, protein and small amount of carbohydrate.

      Membrane is quasi fluid with components held together mostly by non-covalent interaction
      The fluidity of the membrane is α chain length and unsaturation of fatty acids
      The more the un-saturation (no. of double bonds), the more the fluidity of the membrane
      Increased fatty acid chain length decreases fluidity.
      Increased amount of cholesterol decreases fluidity at 37oC
1. Phospholipid bilayer
      Consists of polar hydrophilic (water loving) phosphate head group
      Non polar hydrophobic fatty acid chain
      Forms the structural backbone of the membrane that serves as a barrier to regulate the passage of substances
      Cholesterol  bound with phospholipids makes membrane stable and  highly impermeable to polar molecules
2. Proteins mostly globular
      A) Extrinsic or peripheral proteins are loosely attached to the lipid bi layer and are hydrophilic
      B) Intrinsic, integral or transmembarne proteins may serve as transport channels (permeases, translocases), receptor molecules, antigens etc. It forms about 70% of total membrane proteins
3. Carbohydrates are present on the outer side or extracellular side of the plasma membrane
      Present as glycoprotein or glycoli
      pid (carbohydrates bound to protein or lipid)
      Function : helps in cell recognition, cell interaction and cell adhesion
      As receptors, antigens etc

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Why is genetic code a triplet code? Logical Explanation

The logic behind triplet genetic code or why is the genetic code a triplet code instead of a singlet or doublet?
There are four nitrogenous bases in our DNA. Upon transcription, bases in mRNA are (Adenine A, Guanine G, Uracil U and Cytosine C) and transcribed mRNA codes for proteins. As we already know there are 20 amino acids (essential amino acids) that are coded by these four bases. Let's us consider the following possibilities. 
Genetic code singlet doublet triplet logic diagram

Case I
Now if we consider the genetic code to be singlet then it would be impossible as there are only four bases and that cannot code for 20 amino acids.  If codon is a singlet code then it can code for 4 amino acids only.
Genetic code, possible permutations
Case II:
If the genetic code is a doublet code; that is, an amino acid is coded by 2-nitrogeneous bases on mRNA in a specific sequence, then it can form 16 codons (42=4x4=16), still not sufficient enough to code 20 amino acids, so the genetic code can’t be of two letters. 
Case III: 
If the genetic code is a triplet code, that is, an amino acid is coded by 3-nitrogeneous bases, and then it can form 64 codons (43=4x4x4=64). But we have only 20 amino acids so codons are in excess. Then the possibility is some amino acids may be coded by more than one triplet code.
 Case IV: 
If the genetic code is a 4 letter code, that is, an amino acid is coded by 4-nitrogeneous bases then it can form 256 codons (44=4x4x4x4=256). But we have only 20 amino acid which is way too more. So it can't be 4.
Final verdict:
So the best possibility is for the codon to have 3 nitrogenous bases or each codon is a triplet code. George Gamow (1954) postulated each codon is a triplet code and is encoding the 20 standard amino acids of proteins used by living cells. Moreover, all the codon are specific, they will code for a single amino acid. Several triplets have the same letters but in different sequences and these code for different amino acids. Later by in vitro synthesis, scientists elucidated the triplet codons for all twenty amino acids.
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Immunoprecipitation: Definition, Principle and Procedure

Immunoprecipitation (IP)
Immunoprecipitation is a method that enables the purification of a protein or antigen.
Principle: is antigen –antibody interaction

Definition: It is the technique of precipitating a protein antigen out of solution using an antibody that specifically binds to that particular protein.

Immunoprecipitation IP Procedure
Summarised Procedure
1.  Suitable antibody against the target antigen or protein is added
2.  As antigen-antibody interactions are highly specific, antibody binds to the target antigen and forms an antigen-antibody complex
3.  This antigen-antibody complex is made insoluble by adding protein A or G beads
4.  On centrifugation of solution, antigen-antibody complex pellet down and supernatant can be removed
5.  Continue to pellet the beads with Ag-Ab complex in centrifuge between each wash. In order to minimize background, care should be given to remove the supernatant completely each time.
6.  Resuspend the beads with Ag-Ab complex in loading buffer and mix gently
7.  Boil at 90–100º C for 5–10 minutes to dissociate the Ag-Ab complex from the beads
8.  Centrifuge the sample to pellet the beads
9.  Collect the supernatant carefully and load onto an SDS-PAGE gel to separate proteins prior to Western blot analysis for detection of protein.

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Importance of Sequence Alignment in Bioinformatics

Sequence alignment is the procedure of comparing two (pair-wise alignment) or more multiple sequences by searching for a series of individual characters or patterns that are in the same order in the sequences.
       Pair-wise alignment: compare two sequences
       Multiple sequence alignment: compare more than two sequences
pair-wise and multiple sequence alignment
Pairwise alignment can be either global or local
In global alignment, an attempt is made to align the entire sequence.
          If two sequences have approximately the same length and are quite similar, they are suitable for the global alignment.
          Suitable for aligning two closely related sequences

Local alignment concentrates on finding stretches of sequences with high level of matches
          Finds local regions with the highest level of similarity between the two sequences and aligns these regions without considering the alignment of rest of the sequence regions
          Suitable for aligning more divergent sequences
          Used for finding out conserved patterns in DNA or protein sequences

What is the purpose of sequence alignment?
By finding similarities between sequences
1. Scientists can infer the function of newly sequenced genes by aligning the newly sequenced genes with sequences already in the database
2. Predict new members of gene families
3. Discovering evolutionary relationships or reconstruction of phylogeny
   -To find whether two (or more) genes or proteins are evolutionarily related to each other in closely related species
4. It can be used to predict the location and function of protein-coding and transcription-regulation regions in genomic DNA. Regulatory regions in genome are often conserved therefore presence of such conserved regions easily tells us the regulatory sites in the newly sequenced genes
5. To find structurally or functionally similar regions within proteins
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ICMR JRF 2016 Notification Apply Online Now

ICMR in collaboration with PGIMER, Chandigarh will hold a National level examination for the award of Junior Research Fellowships (JRF), for Indian national candidates.
Exam DateJuly 17, 2016 (Sunday).
ICMR JRF exam 2016
A total of  120 fellowships awarded in Life Sciences stream (like microbiology, physiology, molecular biology, genetics, human biology, biotechnology, biochemistry, bioinformatics, biophysics, immunology, pharmacology, zoology, environmental sciences, botany, veterinary sciences. 
Another 100 candidates would be selected for consideration for positions of JRF under various research schemes of ICMR (subject to fulfilling the conditions for appointment under the schemes) for the duration of that scheme. These JRFs would also be permitted to complete Ph.D. while working in the scheme, if enrolled.  
The validity of result will be two years for placement in ICMR funded projects.
Important Dates
  • Date of opening of Registration: 09.04.2016
  • Last date for filling of online application: 09.05.2016
  • Late date of fee deposit in Bank: 12.05.2016
  • Date of Entrance Examination (Tentative): 17.07.2016
Duration and Emoluments: The existing value of the fellowship is at present Rs. 25000/- (Rupees Twenty Five  thousand only)  Per  month and an annual contingency grant up to Rs. 20,000/- per annum. The local institution shall review the performance of JRF after two years through an appropriate Review Committee constiuted by the Head of the institution. The fellow may be awarded SRF after successful assessment by the Review Committee.
    Age Limit: The age limit for admission to the eligibility test is 28 years (upper age limit relaxable upto 5 years in case of candidates belonging to SC/ST, physically handicapped (PH) and female candidates, 3 years in the case of OBC category.

    Examination fee  a) SC/ST/PH : Rs. 800/- 
                                    b) All other categories (General & OBC) : Rs. 1,000/-

    Examination Centre :  01) Chandigarh, 02) Chennai, 03) Delhi 04) Kolkata, 05) Mumbai, 06) Hyderabad  07) Guwahati 08) Varanasi 09 Bhopal Code Name of the Centre 10) Bhubaneshwar 11) Sri Nagar 12) Bangaluru

    Syllabus: As prescribed by UGC.

    Subjects covered under Life Sciences include microbiology, physiology, molecular biology, genetics, human biology, biotechnology, biochemistry, bioinformatics, biophysics, immunology, pharmacology, zoology, botany, environmental sciences and veterinary science.

    Free ICMR JRF Preparation Resources
    ICMR-JRF Exam + Question Pattern * ICMR-Model QuestionsSample question paper
    ICMR Previous Questions & Answers ( Set 1Set 2Set 3 /Set 4 / Biochemistry / Biostatistics )
    Scheme of Test
    The test will consist of one paper of 2 hours duration. The paper will consist of 2 Sections.
    The Aptitude Section (Section A) will have 50 questions on
    (i) scientific phenomenon in everyday life;
    (ii) general knowledge in sciences; and
    (iii) common statistics.
    All these questions would be compulsory with each question carrying 1 mark. The subject Specific Section (Section B & C) would pertain to (B) Life Sciences and (C) Social Science. 
    The candidate may attempt questions in either of the two areas. Each area of section B & C would have 100 questions and the candidate may attempt any 75 questions in the predesigned area of Section B or C.

    Candidates are required to indicate the option for Section B or C in the application form too.
    Each question carries one mark. Negative marking @ 0.25 will be made for each of
    the wrong answer
    . The questions in both the sections would appear in English only.
    The qualifying marks will be 55% obtained in both the sections (A+B or C) for General
    Category and OBC and 50% for SC/ST and physically handicapped.
    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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    10 Quick Facts about Zika Virus

       Fact 1: About the Zika virus
    • Zika fever is caused by the Zika virus (ZIKV), an arthropod-borne virus (arbovirus).
    • The Zika virus is a member of the Flavivirus genus in the family Flaviviridae.

    • RNA virus
    • It is related to dengue, yellow fever, West Nile and Japanese encephalitis, viruses that are also members of the virus family Flaviviridae.

    Fact 2: Why the name ‘Zika’?
    • First identified in Uganda in 1947 in rhesus monkeys.  It is named after the ‘Zika forest’ in Uganda.
    • It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania.

    • The virus is known to circulate in Africa, the Americas, Asia and the Pacific.
        Fact 3: About the vector
    • The vector is Aedes mosquitoes mainly Aedes aegypti 
    Fact 4: Symptoms

    Fact 5: Diagnosis
    Laboratory testing for the presence of Zika virus RNA in the blood or other body fluids, such as urine or saliva.
    Fact 6: Treatment
    • No specific treatment or vaccine currently available. Zika virus disease is usually relatively mild and requires no specific treatment. If symptoms last for a longer period, seek medical attention.
    • The best form of prevention is protection against mosquito bites.
    Fact 7: Why Zika is considered dangerous?
    Potential complications: Two major diseases seem to be associated with Zika disease. They are

    a) Guillain-Barré Syndrome (GBS) is an autoimmune disease in which a person’s own immune system damages their nerve cells, causing muscle weakness and sometimes even paralysis.

    b) Microcephaly is a medical condition in which the brain does not develop properly resulting in a smaller than normal head. Recent report from Brazil suggests increased incidents of babies born with microcephaly from infected mother.
    Fact 8: Mode of Transmission
    • Primarily through the bite of an infected Aedes species mosquito (A. aegypti and A. albopictus)
    • Mother to child: A mother already infected with Zika virus near the time of delivery can pass on the virus to her newborn around the time of birth.
    • Zika virus can be spread by a man to his sex partners.

          The virus can survive in semen longer than in blood.
    Fact 9: “Still largely unknown”
    •  The mechanism of viral infection yet to be discovered.
    Fact 10: Global incidence of Zika?
    •  Many scientists suggest global warming as a reason for transmission of virus to low temperature countries. Rise in temperature favors the survival of mosquitoes, the vector of Zika virus.


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    59.75%- The cut off Percentage of CSIR UGC NET JRF Life Sciences December 2015

    To check the result Click this link 1. Result-CSIR UGC NET JRF in Life Sciences December 2015 
    To know your marks Click this link 2. Marks obtained-CSIR UGC NET JRF Life sciences December 2015
    Hearty congrats for the qualifiers..... and congrats for the aspirants as you are so close to your dream... 
    The cutoff percentage for CSIR UGC NET JRF  life sciences for the year 2015 December 
    was 59.75%.
     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.

    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”…..The following links may help you...
    Happy learning and best wishes for the exam....    From Biologyexams4u team
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    CSIR UGC NET JRF Life Sciences 2016 June Apply Online

    CSIR will hold   the Joint CSIR-UGC Test on 19th June, 2016 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
    Exam DateCSIR-UGC JRF(Junior Research Fellowship)& NET (Eligibility for Lectureship) :19th June, 2016.
    Important Dates:

    Age Limit & Relaxation:
    • For Junior Research Fellowships  (JRF):Maximum 28 years as on 01-01-2016 (upper age limit may be relaxed up to 5 years in case of candidates belonging to SC/ST/OBC, Physically handicapped/Visually handicapped and female applicants).
    • For LS (NET): No upper age limit.
    Educational Qualification:
    • BS-4 years program/BE/BTech/BPharma/MBBS/Integrated BS-MS/MSc or equivalent degree with at least 55% marks for general and OBC (50% for SC/ST candidates, physically and Visually Handicapped candidates).
    • Candidates enrolled for M.Sc or having completed 10+2+3 years of the above qualifying examination are also eligible to apply in the above subject under the Result Awaited (RA) category on the condition that they complete the qualifying degree with requisite percentage of marks within the validity period of two years to
      avail the fellowship from the effective date of award.
      Such candidates will have to submit the attestation format (Given at the reverse of the application form) duly certified by the Head of the Department/Institute from where the candidate is appearing or has appeared.
    • BSc (Hons) or equivalent degree holders or students enrolled in Integrated MS-PhD program with at least 55% marks for general and OBC candidates; 50% marks for SC/ST candidates, physically and visually handicapped candidates are also eligible to apply.Candidates with bachelor’s degree, whether Science, engineering or any other discipline, will be eligible for fellowship only after getting registered/enrolled for PhD/Integrated PhD program within the validity period of two years.
    • The eligibility for lectureship of NET qualified candidates will be subject to fulfilling the criteria laid down by UGC. PhD degree holders who have passed Master’s degree prior to 19th September 1991, with at least 50% marks are eligible to apply for Lectureship only.
      The question paper shall be divided into three parts, (A, B & C) as per syllabus & Scheme of Exam.
      Part 'A' shall be common to all subjects including Engineering Sciences. This part shall contain questions pertaining to General Aptitude with emphasis on logical reasoning, graphical analysis, analytical and numerical ability, quantitative comparison, series formation, puzzles etc.
      Part 'B' shall contain subject-related conventional Multiple Choice questions (MCQs), generally covering the topics given in the syllabus.
      Part 'C' shall contain higher value questions that may test the 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.
      Negative marking for wrong answers, wherever required, shall be applicable as per subject wise scheme of Exam.
      Examination fee:

      Examination Centres: 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.
      Exam Result& Validity period of fellowship:
      The final result of this Single MCQ test may be declared sometime in the month of March/April, 2016 and fellowship to successful candidates will be effective from 1 st January 2017 with the validity period of 2 years for joining the fellowship under CSIR Scheme.
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