UPSC – IFS (Indian Forest Service) Exam Previous Year Question Paper
IFS – 2013 – Zoology Main Paper I (PDF)
Official / Original Previous Year (Old) Solved Question Paper of UPSC (Union Public Service Commission) IFS (Indian Forest Service) Zoology Main Examination – Paper I and Paper II. IFS Exam 2013 Zoology Main Paper I. IFS aspirants can download the question paper as single PDF file for your exam preparation. To download the question paper please click on the download button below the preview.
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Endonuclease vs Exonuclease (Similarities and Differences between Endonuclease and Exonuclease Enzyme)
Nucleases are a class of enzyme which hydrolyzes the nucleic acids such as DNA and RNA. They hydrolyze the phosphodiester backbone which connects individual nucleotides in a polynucleotide. There are two broad categories of nucleases depending upon their site and mode of action on the nucleic acid. They are Endonucleases and Exonucleases.
Endonucleases: Endonucleases cleaves the phosphodiester bond in the polynucleotide from the interior (endo). They hydrolyze the phosphodiester bonds present within a polynucleotide chain. Some endonucleases are non-specific and they can cut the phosphodiester bond between any nucleotides. A special class of endonucleases, called restriction endonucleases (restriction enzymes), is very specific in their action and they cut at a specific sequence in the polynucleotide chain called the Restriction Site. Restriction endonuclease has immense application in recombinant DNA technology.
Retinoblastoma Protein (pRb) – A Tumor Suppressor Gene/Protein (The Importance of pRb in Cell Cycle Regulation and Cancer)
What is Retinoblastoma?
What is the cause of Retinoblastoma?
Retinoblastoma or RB is a type of cancer affecting the retina of young individuals. RB occurs in the human population both spontaneously and as a heritable disorder. The genetic reason for the occurrence of RB is associated with a structural aberration of the chromosome. In human, the Rb gene is present on the chromosome 13 at the q-14 region. The loss of this region of due to deletion or mutation causes the retinoblastoma.
The condition of retinoblastoma arises only when both the copies of the Rb gene are lost. In the inherited form of the disease, one parental chromosome carries an alteration in this region. A spontaneous mutation in the retinal cells which results in the inactivation of the other copy of Rb gene can cause the tumor development. Thus, the loss of function of Rb protein due to mutation or deletion is the cause of retinoblastoma.
How Rb acts as a tumor suppressor gene?
A tumor suppressor gene is a gene that prevents the development of cancer. When this gene is mutated and its function is lost forever, there is a very high chance of the cell to enter into a cancerous growth.
TMC ACTREC JRF for Ph.D in Life Sciences, Notification, 2016
TATA MEMORIAL CENTRE Advanced Centre for Treatment, Research and Education in Cancer (ACTREC)
(A Grant-in-Aid Institution of the Department of Atomic Energy, Government of India)
Applications are invited, in the prescribed format, for the award of JUNIOR RESEARCH FELLOWSHIPS(JRF 2016) for Ph.D. in Life Sciences at Tata Memorial Centre. The Tata Memorial Centre (TMC) is an autonomous Grant-in-aid Institution of the Department of Atomic Energy. The TMC is comprised of the Advanced Centre for Treatment, Research and Education in Cancer (ACTREC) and the Tata Memorial Hospital (TMH). The TMC conducts Ph.D. program in Life Sciences and is affiliated to the Homi Bhabha National Institute (Deemed University).
On-going research at TMC includes basic and translational research in Cancer Biology. Specific research topics include study of cell proliferation, differentiation, apoptosis, metastasis, tumor immunology, molecular imaging, carcinogenesis, stem cell biology, biophysics, structural biology, bioinformatics, proteomics, genomics, genetics, epigenetics.
Qualifications: M.Sc. (Applied Biology / Biochemistry / Bioinformatics / Biophysics / Biotechnology / Botany / Life Sciences / Microbiology/ Molecular Biology / Zoology or related Biological Sciences) / M.Tech. (Bioinformatics/ Biotechnology); M.V.Sc.; M.Pharm. from a recognized University, with ³ 60% aggregate marks. Those awaiting results may also apply. Candidates having done post-graduation course of only 1 year duration are not eligible.
Stipend: Rs. 25000/-+ 30% HRA (if hostel facility is not allotted) per month as applicable. Limited hostel facility is available on the ACTREC campus on first come, first served basis.
The XX -XY Sex Chromosomal Mechanism of Sex Determination in Plants
Majority of the flowering plants are monoecious with male and female reproductive parts are borne on the same flowers or different flowers of same plant. Only about 6% of Angiosperms are dioecious (male and female flowers on separate plants). The studies of sex determination mechanisms in plants were done only in very few species, such as Coccinia, Asparagus and Melandrium. Melandrium album or Silene latifolia (synonym) is a dioecious model plant in genetics belongs to the Family Caryophyllaceae. The diploid chromosome number of Melandrium album is 24 (n = 12).
This post describes the genetic mechanism of sex determination in Melandrium album or Silene latifolia.
Melandrium album shows sex chromosomal sex determination. They have X and Y sex chromosomal constitution similar to Drosophila and Human. However, the mechanism of sex determination is quite different from the usual XX – XY system. In Melandrium album, the AAXX individuals will be females and AAXY individuals will be males.
The Y chromosome plays a crucial role in the sex determination of Melandrium album. The Y chromosome contains male determining genes and female suppressing genes, both are necessary for the development and maturation of fertile anthers in the male plants. Since the female individuals are homogametic, (produce only one type of gametes – XX constitution) the segregation of X and Y chromosomes occurs only in the male individuals during meiosis.
Usually plants with AAXY chromosomal constitution are males. Sometimes AAXY individuals will be hermaphrodite (bisexual) or androhermaphrodites (forming both bisexual and male flowers on the same individuals). The formation of bisexual individuals in AAXY individuals may be due to the mutation or deletion of the female suppressing genes on the Y chromosome or due to the change in DNA methylation pattern.
Mechanism of sex determination in Melandrium album: