i What is meant by the term gene expression 2. What is meant by the term regulat
ID: 134254 • Letter: I
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i What is meant by the term gene expression 2. What is meant by the term regulation 3. What are the stages in which a gene could be regulated 4. What is an activator how does it act s. What is a repressor how does it act? 6. Why does DNA methylation occurs and on which nucleotide 7. What does presence and/or absence of tryptophan do to the s. What does presence and absence of glucose and lactose do to 9. Give an example of how alternative splicing results in 10. What is miRNA, RNA interference and SiRNA in gene tryptophan synthesizing gene the lactose promoter expression of different proteins in two different organs expression 11. What is essential for a ribosome to control translation on mRNA in term of start site orientationExplanation / Answer
1.Gene Expression: Synthesis of a perticular protein as per the sequence of bases in the perticular gene is known as gene expression. This protein will either work structurally or as an enzyme to control a perticular trait. Some genes are non protein coding such as genes coding for tRNA and rRNA etc.
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2. Regulation: Regulation means any step or mechanism that control the expression of any gene.Regulation involve many factors like cyclin and cdk (cyclin dependant kinase) in cell division, Methylation at adenine in replication etc.
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3. Stages of gene regulation: There are following steps -
a) Transcriptional regulation
b. Post transcriptional regulation
c. Translation level regulation
d. Post translational regulation
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4. Activator: Activator are the components that enhance the expression of genes. It intract with DNA at Promoter site example in Lac operon, cAMP act as activator, it bind at promotor site and facilitate the binding of RNA polymerase to DNA.
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5. Repressor: Repressor are protein or other non protein compounds that inhibits the gene expression. for example in Lac operon model, repressor protein formed by regulator, bind at operator site and inhibit the transcription of structural gene by RNA polymerase.
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6. DNA methylation: DNA methylation occurs at adenine base in Prokaryotes and it represent the origin site of replication. In Eukaryotes, methylation at any site may repress the gene expression. It occurs mainly on Guanine.
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7. Tryptophan synthesizing genes are switched ON when tryptophan is not present in media. Whn tryptophan is binds with aporepressor protein and make it active repressor that can bind with operator site of gene and make it SWITCH OFF.
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8. Presence of glucose in media switch OFF lactose operon gene because in the presence of glucose, cAMP level remains low and it can not bind to lactose promotor so lac operon reain switch off. In the presence of lactose, Lac operon remain switch on because lactose bind with repressor protein and inhibit its binding at operator region. So repressor are not inhibit the gene expression.
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10. miRNA (microRNA) are short non-coding RNAs that regulate gene expression post-transcriptionally. They generally bind to the 3'-UTR (untranslated region) of their target mRNAs and repress protein production by destablizing the mRNA and translational silencing.RNA interference means silencing the mRNA by its binding with small complementary RNA molecule. Many siRNA are used to silence the mRNA to inhibit the production of particular protein.
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11: During the initiation of protein biosynthesis, the gene expression can be regulated via some structural elements. these elements are presented at the '5 untranslated region(UTR) of mRNAs. These elements made up of folded mRNA segments. These segments bind to the ribosomes and block the translation until the mRNA will unfolds.
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