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    • Genetics (from Ancient Greek ????????? genetikos, "genitive" and that from ??????? genesis, "origin"),[1][2][3] a discipline of biology, is the science of genes, heredity, and variation in living organisms.[4][5]

    Genetics deals with the molecular structure and function of genes, with gene behavior in the context of a cell or organism (e.g. dominance and epigenetics), with patterns of inheritance from parent to offspring, and with gene distribution, variation and change in populations. Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, through plants (especially crops) and domestic animals, to humans (as in medical genetics).

    The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-19th century.[6] Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes.

    Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit. DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as a template for creating a new partner strand. This is the physical method for making copies of genes that can be inherited.

    The sequence of nucleotides in a gene is translated by cells to produce a chain of amino acids, creating proteins—the order of amino acids in a protein corresponds to the order of nucleotides in the gene. This relationship between nucleotide sequence and amino acid sequence is known as the genetic code. The amino acids in a protein determine how it folds into a three-dimensional shape; this structure is, in turn, responsible for the protein's function. Proteins carry out almost all the functions needed for cells to live. A change to the DNA in a gene can change a protein's amino acids, changing its shape and function: this can have a dramatic effect in the cell and on the organism as a whole.

    Although genetics plays a large role in the appearance and behavior of organisms, it is the combination of genetics with what an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining an organism's size, the nutrition and health it experiences after inception also have a large effect.

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    Researchers at The University of Texas M.D. Anderson Cancer Center have found that gene therapy if delivered directly to a particular type of breast cancer cell causes the cell to self-destruct, there
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    Mutations in the breast cancer susceptibility 1 (BRCA1) gene significantly increase the chance of developing breast and ovarian cancers. However the mechanisms at play are not fully understood. Now, researchers at Virginia Commonwealth University Massey Cancer Center have shown that certain BRCA1 mutations result in excessive, uncontrolled DNA repair, which challenges the prior assumption that mutations in BRCA1 only contribute to breast cancer through a reduction in function. Recently
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    The targeted drug Xalkori™ (crizotinib) has been approved by the US Food and Drug Administration for the treatment of advanced non-small lung cancer that has an abnormal version of the ALK gene. Lung cancer is the leading cause of cancer death in the US and around the world, highlighting the importance of developing effective new approaches news.cancerconnect.com


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    BACKGROUND:Single nucleotide polymorphisms (SNPs) in nucleotide excision repair (NER) pathway genes may modulate DNA repair capacity and increase susceptibility to breast cancer (BC). A case-control study was conducted by evaluating genes involved in DNA repair to identify polymorphisms associated with BC.METHODS:The 384 SNPs of 38 candidate genes were genotyped using the Illumina GoldenGate method. Genotypes were determined in a case-control study that consisted of 346 BC patients and 361 controls. Odds ratios and 95% confidence intervals were computed using logistic regression models. Multiple logistic regression models adjusted for age, family history of BC, and body mass index were used.RESULTS:Gene–gene interaction analysis among the DNA repair pathway genes showed significant effects on BC risk. ERCC2 rs50872 (TC genotype) in combination with XPA rs2808668 (TC genotype) and rs1800975 (AG genotype) was strongly associated with an increased risk of BC (P = .0004 and .0002, PBonferroni = .023 and .014, respectively). Moreover, the T-G (including rs2808668 and rs1800975) haplotype in XPA combined with the ERCC2 T allele in rs50872 carriers was also associated with additive risk effect of BC (odds ratios: 2.58, 2.62, and 3.49, respectively).CONCLUSION:Genetic variation in DNA repair genes involved in NER mechanisms increased the risk of BC development. These results suggested that a stronger combined effect of SNPs via gene–gene interaction may help to predict BC risk. Cancer 2011;. © 2011 American Cancer Society.dx.doi.org


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