How does the structure of DNA (double helix) determine how the genetic information is passed on?
The DNA double helix has a complex molecular structure owing to the chemical features of its polynucleotide chains. The double helix consists of two polynucleotide strands running in antiparallel directions, bound by hydrogen bonds. This is often between the bases of the two strands. The nucleotides in these strands contain discrete units called genes, which carry the necessary genetic information required for the proper functioning of the cell and the organism as a whole. The entire collection of information in the DNA is known as the genome and contains the information to be transmitted to the subsequent generation. The information included in the genomes is staggering. A human cell contains DNA of approximately two meters in length; histones wind the DNA to form the condensed chromosomes that can easily fit into the cells. During replication, this DNA needs to be relaxed and unwound, carried out by helicase, to allow replication proteins to bind to specific regions of DNA and carry out their function. Both strands of the DNA are then used as the template to synthesize daughter strands. DNA replication is a stringent process ensuring the same genetic information transmitted to daughter cells (Alberts et al., 2002).
How does the cell use the information contained in the DNA to construct proteins (transcription and translation)?
Protein synthesis occurs in two highly controlled significant steps, which are translation and transcription. Most genes contain key elements such as the promoter, open reading frame in their sequence necessary for protein synthesis. The first step is transcription, where the information in the DNA arrangement is recorded into messenger RNA (mRNA).
The DNA unwinds and separates to form an open complex, RNA polymerase initiates the process by binding to the promoter region of the template strand, and elongating is the step where the RNA polymerase moves along the template synthesis the mRNA molecule. Step three is chain termination in eukaryotes termination done by the addition of adenine nucleotide in the 3’of RNA transcribe the process is polyadenylation. The final step is processing where the introns are removed and exons are spliced with a mature mRNA molecule.
Eukaryotic mRNA requires posttranscriptional modifications such as splicing to produce the mature RNA, which can now be translocated to the site of protein synthesis example the cytoplasm.
The next step is a translation where the mRNA is converted into protein. In this process, the multifaceted ribosomal RNA (rRNA), containing the acceptor, peptidyl, and exit sites, binds to the ribosomal binding site of the mRNA (a few base pairs upstream of the start codon) and initiates protein translation. The message in mRNA is carried in the form of codons i.e. a structure of three nucleotides that code for a specific amino acid, which is read by rRNA (Barber&Elledge, 2019). A separate RNA called transfer RNA (tRNA) carries amino acids to the rRNA where they are transferred from tRNA to the expanding peptide chain. This process of protein assembling stays until the ribosome encounters a stop codon example (UAA, UAG, UGA) and the peptide chain is released. Finally, the post-translation modification includes the 5’capping,3’polyadenylation, and RNA splicing to release a mature protein. Using translation and transcription biological information contained in the genes is converted to biologically active molecules i.e. proteins (Barber&Elledge, 2019).
How gene expression is regulated (give three different forms of regulation mechanisms)?
Eukaryotes in gene expression comprise many steps during the regulation process. The majority of the genes are regulated the primary levels of transcription. The transcriptional regulatory proteins are accountable for the gene expression during differentiation and development. The proteins contain a significant aspect of enhancers that combine different regulatory proteins where they work together in the regulation of gene expression. The immunoglobulin is known to spans almost 200 pairs and has nine distinct sequence elements serving as protein binding sites. The immunoglobulin is active in the lymphocytes. The regulatory sequence is responsible for specific tissue-specific expression. The home domain proteins also play a fundamental function in the regulation of gene expression during the process of embryonic development. It was discovered as being developmental mutants in Drosophila. In chromatin accessibility, one of the Eukaryotic steps here, the genes can be regulated since it makes them readily available for the transcription process. Also, transcription is acknowledged as being the critical point of the regulatory of many genes. The set of factors in transcription binds to exact DNA order, and therefore, it contains or promotes it to the RNA. Lastly, RNA processing can be used to regulate gene expression whereby the RNA molecule is controlled and can exit from the nucleus (Brooker, 2012) also the RNA molecule splicing to produce more proteins from a single gene is regulated.
How does gene regulation relate to cancer development?
Cancer result from the gene which is not expressed in a cell but due to mutation levels the gene is switched on and expressed at high levels. Alteration in histone acetylation, increased translational control, post-modification, and increased RNA stability is detected in the cancer cells.
Today, cancer is considered as the most chronic condition among human beings. Typically, cancer occurs due to the alterations of gene expression caused by mutation. Modifications in transcription and epigenetic regulation are detected in cancer. Epigenetics is the process of changing the cellular phenotype other than changes in the underlying DNA sequence this results in gene suppression thus resulting in cancer. Also, the mutations affect the growth rate through the cell cycle. Alterations in the body cells are the primary cause of the development of cancer, thus influencing the transcriptional process of which helps in gene regulation. For instance, in breast cancer, their many proteins are overexpressed, thus causing gene mutation. As a result, there is increased phosphorylation, which is a major transcription factor. Therefore, overexpression in epidermal growth is the leading cause of breast cancers among human beings. Cancer alters the expression of miRNA through building RNA molecules. The molecules degrade due to the overexpression of the miRNA, thus affecting the regular cellular activity (Brooker, 2012). For instance, in cases where there is too much MiRNA, it leads to a decrease in the RNA Population, resulting in a reduction of protein expression. Notably, the appearance of wrong proteins in the body considerably affects the cell functioning, and this contributes to the development of cancer. For instance, in colon cancer, the expression of cells increases cell growth instead of cell completely dying. Cancer develops due to mutations that occur in the protein (Brooker, 2012).
Moreover, cancer may develop due to structural rearrangements whereby the pieces of DNA may move from one part of the genome to another. Cancer is a genetic disease that is clonal and usually starts when single cells are acquired in the series of mutations. The alterations of protein modifications and enlarged translational control are generally observed in the cancer cells during the process of gene regulation. The proto-oncogenes, which are referred to as being positive cell regulators, maybe mutated to became oncogenes hence causing cancer. Overexpression of oncogenes can alter the transcription activity and protein translation. The gene helps in the specialization and division of the healthy cells. However, normal cells may have genes that prevent inappropriate growth. For instance, the suppressor genes help in controlling cell growth in normal cells. Therefore, a gene mutation in the cells is reduced drastically. The overexpression of the genes normally leads to the alteration of transcriptional activities and protein stability. Therefore, the need for gene regulation is critical in reducing the cells’ overexpression. The transcription factors are essential in regulating the cell cycle since they help in determining the cell division process. However, the alterations affect transcriptional control, thus leading to the rise of cancer. The growth of modified cells is due to an increase in transcriptional activation (Brooker, 2012).
Conclusion
References
Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). The structure and function of DNA. In Molecular Biology of the Cell. 4th edition. Garland Science.
Barber, K. W., & Elledge, S. J. (2019). Sequencer Hacking Unlocks Quantitative Protein Studies. Molecular cell, 73(5), 863-865.
Brooker, R. J. (2012). Concepts of genetics. New York, NY: McGraw-Hill.