Question

9) In your own words, explain how gene expression can be regulated by miRNAs. Choose a gene of your choice and explain how miRNAs could be used to elucidate its function. Include your hypothesis and expected results from your proposed experiment (10 points). aculated by mininas, Choose asene of your

Answer 1

miRNAs (microRNAs) 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 destabilizing the mRNA and translational silencing. The exact mechanism of miRNA-mediated translational repression is yet to be fully determined, but recent data from our laboratory have shown that the stage of translation which is inhibited by miRNAs is dependent upon the promoter used for transcribing the target mRNA.

Human Genes:-

The more complex the organism, the more complex its genome and the higher the number of genes. The Human Genome Project estimates that around 30,000 human genes provide the codes for the proteins that create each person’s unique anatomical and physiological identity.

The human genome contains approximately three billion base pairs as subunits of deoxyribonucleic acid nucleotide monomers. The sequence of these base pairs forms the code of each gene, and each gene provides the transferable data for one or more proteins.

The Forkhead box protein P2 (FOXP2) gene encodes a transcription factor. The FOXP2 gene is found at the same chromosomal loci in every human cell (except mature red blood cells), but is only expressed in the brain, the gut and in the lung. This particular transcription factor binds with DNA but is not limited to a single function as it has the ability to bind with hundreds of DNA promotors and therefore, as previously mentioned, can contribute to the production of more than one protein. However, one of FOXP2’s primary functions is in the human development of speech and language. We know this because mutations in the FOXP2 gene lead to ‘autosomal dominant speech and language disorder with orofacial dyspraxia’, or SPCH1.

The BRCA gene mutation is well known as a cause of breast cancer. Usually, the BRCA genes stop tumor formation by repairing DNA damage caused by pollution, diet, lifestyle habits such as smoking, exposure to radiation, and many other factors. In humans with mutated or damaged BRCA genes, this protection no longer applies. Men and women with BRCA mutations either at locus 17q21 (BRCA 1) or 13q12.3 (BRCA 2) have a much higher risk of developing breast cancer, and females have a higher risk of developing ovarian cancer.

The COL1A1 gene encodes a single component of alpha-1 type I collagen, a protein found in many types of connective tissue. This gene can be found at locus 17q21.33. This ‘address’ refers to the COL1A1 gene’s position on the 17th chromosome, more specifically on the longer ‘q’ arm, and in region 2, band 1, sub-band 33.

MTHFR gives the code the human body requires in order to manufacture methylenetetrahydrofolate reductase. A mutation in the MTHFR gene is actually quite common, and this result means hindrance or an inability to carry out steps within the process of manufacturing end products such as homocysteine and the nucleoside thymidine. This can lead to hyperhomocysteinemia which leads to certain vitamin B deficiencies; one of these, vitamin B9 (folic acid), is necessary for embryonal neural development.

CXorf38 is another gene that codes proteins for tissue formation. Cxorf38 is predominantly expressed in glands and lymph nodes and can be found at locus Xp11.4, which indicates the X chromosome (non-autosomal chromosome or sex chromosome), the shorter ‘p’ arm, region 1, band 1, sub-band 4. This locus is pictured below.

- Xp22.32 Xp22.2 Xp22.12 - Xp21.3 Xp21.1 Xp11.4 Xp11.22 (TIITTICIITTIIT TID - Xq12 -Xq13.2 Xq21.1 +Xq21.31 - Xq21.33 Xq22.2 Xq23 + X225 Xq26.2 Xq27.1 -Xq27.3

X-chomasome loci