File Name: biological importance of dna and rna .zip
By convention, sequences are usually presented from the 5' end to the 3' end. For DNA, the sense strand is used. Because nucleic acids are normally linear unbranched polymers , specifying the sequence is equivalent to defining the covalent structure of the entire molecule.
DNA deoxyribonucleic acid is the genomic material in cells that contains the genetic information used in the development and functioning of all known living organisms. DNA, along with RNA and proteins, is one of the three major macromolecules that are essential for life. Within the nucleus of eukaryotic cells, DNA is organized into structures called chromosomes. The complete set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes.
DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases bases. It is the sequence of these four bases along the backbone that encodes information.
The sequence of these bases comprises the genetic code, which subsequently specifies the sequence of the amino acids within proteins. Bases are classified into two types: the purines, A and G, and the pyrimidines, the six-membered rings C, T and U. Uracil U , takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring.
Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine. In the DNA double helix, each type of base on one strand normally interacts with just one type of base on the other strand.
This is complementary base pairing. Therefore, purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G. Furthermore, DNA is never translated directly to protein.
The Central Dogma of Molecular Biology. Cell division is essential for cells to multiply and organisms to grow. As the final step in the Central Dogma, DNA replication must occur in order to faithfully transmit genetic material to the progeny of any cell or organism. When a cell divides, it must correctly replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. This enzyme makes the complementary strand by finding the correct base through complementary base pairing.
In this way, the base on the old strand dictates which base appears on the new strand, and the cell ends up with a perfect copy of its DNA. This process typically takes place during S phase of the cell cycle.
A gene is a DNA sequence that contains genetic information for one functional protein. Proteins are essential for the modulation and maintenance of cellular activities. The amino acid sequence of each protein determines its conformation and properties e. Directed protein synthesis follows two major steps: gene transcription and transcript translation. Transcription is the process by which the genetic information stored in DNA is used to produce a complementary RNA strand.
Genes consist of sequences encoding mRNA exons that are interrupted by non-coding sequences of variable length, called introns. Introns are removed and exons joined together before translation begins in a process called mRNA splicing. Messenger RNA splicing has proved to be an important mechanism for greatly increasing the versatility and diversity of expression of a single gene. It takes place in the nucleus in eukaryotes and in the cytoplasm in bacteria and archaea and leads to the formation of mature mRNA.
Several different mRNA and protein products can arise from a single gene by selective inclusion or exclusion of individual exons from the mature mRNA products. It permits a single gene to code for multiple mRNA and protein products with related but distinct structures and functions 1. Once introns are excised from the final mature mRNA molecule, this is then exported to the cytoplasm through the nuclear pores where it binds to protein-RNA complexes called ribosomes 2. DNA transcription. Although every somatic cell in the human body contains the same genome, activation and silencing of specific genes in a cell-type-specific manner is necessary.
Moreover, a cell must silence expression of genes specific to other cell types to ensure genomic stability. This type of repression must be maintained throughout the life of each cell in normal development. Epigenetic modifications that are defined as heritable, yet reversible changes that influence the expression of certain genes but with no alteration in the primary DNA sequence are ideal for regulating these events.
The best studied epigenetic modification in human is DNA methylation, however it becomes increasingly acknowledged that DNA methylation does not work alone, but rather occurs in the context of other epigenetic modifications such as the histone modifications. Epigenetic Modifications. RNA, is another macromolecule essential for all known forms of life. The chemical structure of RNA is very similar to that of DNA: each nucleotide consists of a nucleobase a ribose sugar, and a phosphate group.
Among the ncRNAs, microRNAs miRNAs represent the best-studied class to date and have been shown to regulate the expression of their protein-coding gene targets in a sequence-dependent manner 10 — An RNA molecule is said to be monocistronic when it captures the genetic information for a single molecular transcriptional product, e.
Most eukaryotic mRNAs are indeed monocistronic. In the case of polycistronic mRNAs, the primary transcript comprises several back-to-back mRNAs, each of which will be eventually translated into an amino acid sequence polypeptide. Such polypeptides usually have a related function they often are the subunits composing a final complex protein and their coding sequences are grouped into a single primary transcript, which in turn permits them to share a common promoter and to be regulated together.
MRNAs carry the genetic information that directs the synthesis of proteins by the ribosomes. All cellular organisms use mRNAs. The structure of an mRNA. RNA interference is a process that moderates gene expression in a sequence dependent manner. The RNAi pathway is found in all higher eukaryotes and was recently found in the budding yeast as well. SiRNAs are double-stranded ncRNAs that are mainly delivered to the cell experimentally by various transfection methods although they have been described to be produced form the cell itself SiRNAs are typically designed to be perfectly complementary to their targets.
RNA interference in mammalian cells. Designer siRNAs are now widely used in the laboratory to down-regulate specific proteins whose function is under study. At the same time, the ability to engage the RNAi pathway in an on demand manner suggests the possibility that RNAi can be used in the clinic to reduce the production of those proteins that are over-expressed in a given disease context. The delivery method remains an important consideration for the development of RNAi-based therapies as the active molecule needs to be delivered efficiently and in a tissue-specific manner in order to maximize impact and diminish off-target effects.
The expression of proteins is determined by genomic information, and their presence supports the function of cell life. These RNA transcripts have been referred to as ncRNAs and there is increased appreciation that many of them are indeed functional and affect key cellular processes. There are many recognizable classes of ncRNAs, each having a distinct functionality.
The full extent of distinct classes of ncRNAs that are encoded within the human genome is currently unknown but are believed to be numerous. The biological role of long ncRNAs as a class remains largely elusive. Several specific cases have been shown to be involved in transcriptional gene silencing, and the activation of critical regulators of development and differentiation: these exerted their regulatory roles by interfering with transcription factors or their co-activators, though direct action on DNA duplex, by regulating adjacent protein-coding gene expression, by mediating DNA epigenetic modifications, etc.
This is known to occur in the case of retroviruses, such as HIV, as well as in eukaryotes, in the case of retrotransposons and telomere synthesis. Post-transcriptional modification is a process in cell biology by which, primary transcript RNA is converted into mature RNA.
This process is vital for the correct translation of the genomes of eukaryotes as the human primary RNA transcript that is produced as a result of transcription contains both exons, which are coding sections of the primary RNA transcript and introns, which are the non coding sections of the primary RNA transcript.
The cap and tail protect the mRNA from enzyme degradation and aid its attachment to the ribosome. A protein is a molecule that performs reactions necessary to sustain the life of an organism.
One cell can contain thousands of proteins. Following transcription, translation is the next step of protein biosynthesis. In translation, mRNA produced by transcription is decoded by the ribosome to produce a specific amino acid chain, or a polypeptide, that will later fold into a protein. Ribosomes read mRNA sequence in a ticker tape fashion three bases at a time, inserting the appropriate amino acid encoded by each three-base code word or codon into the appropriate position of the growing protein chain.
This process is called mRNA translation. Each amino acid is encoded by a sequence of three successive bases. Some specialized codons serve as punctuation points during translation. All proteins thus begin with a methionine residue, but this is often removed later in the translational process. The completed polypeptide chain then folds into a functional three-dimensional protein molecule and is transferred to other organelles for further processing or released into cytosol for association of the newly completed chain with other subunits to form complex multimeric proteins.
Protein translation. Post-translational modification is the chemical modification of a peptide that takes place after its translation. They represent one of the later steps in protein biosynthesis for many proteins. During protein synthesis, 20 different amino acids can be incorporated in order to form a polypeptide. In addition, enzymes may remove amino acids from the amino end of the protein, or even cut the peptide chain in the middle.
This amino acid is usually taken off during post-translational modification. Other modifications, like phosphorylation, are part of common mechanisms for controlling the behavior of a protein, for instance activating or inactivating an enzyme.
Home Learn! DNA 1. DNA transcription 1. Regions of DNA in the human genome, ranging from 0. Approximately half of all gene promoters have CpG islands that when methylated lead to transcriptional silencing. Aberrant DNA methylation patterns have been described in various human malignancies. In particular, global hupomethylation has been implicated in the earlier stages of carcinogenesis, whereas hypermethylation of tumour suppressor genes has been implicated in cancer progression 3.
DNA hypomethylating agents are used for the treatment of certain haematological malignancies. Nucleosome is the basic unit of DNA packaging within the nucleus and consists of base pairs of genomic DNA wrapped twice around a highly conserved histone octamer, consisting of 2 copies each of the core histones H2A, H2B, H3 and H4.
The histone tails may undergo many posttranslational chemical modifications, such as acetylation, methylation, phosphorylation, ubiquitylation, and sumoylation. Histone modifications act except for chromatin condention and transcriptional repression in various other biological processes including gene activation and DNA repair 4. Epigenetic Modifications 2.
DNA deoxyribonucleic acid is the genomic material in cells that contains the genetic information used in the development and functioning of all known living organisms. DNA, along with RNA and proteins, is one of the three major macromolecules that are essential for life. Within the nucleus of eukaryotic cells, DNA is organized into structures called chromosomes. The complete set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases bases.
RNA. CHAPTER 4. DNA AND RNA. Table Some important types of RNA. Name The RNA nucleotides may pair with either DNA or other RNA molecules. When depicts the structure of the biologically active hemoglobin molecule.
Steve Minchin, Julia Lodge; Understanding biochemistry: structure and function of nucleic acids. Essays Biochem 16 October ; 63 4 : — Nucleic acids, deoxyribonucleic acid DNA and ribonucleic acid RNA , carry genetic information which is read in cells to make the RNA and proteins by which living things function. The well-known structure of the DNA double helix allows this information to be copied and passed on to the next generation. In this article we summarise the structure and function of nucleic acids.
The code within our DNA provides directions on how to make proteins that are vital for our growth, development, and overall health. DNA stands for deoxyribonucleic acid. DNA is a vitally important molecule for not only humans, but for most other organisms as well. But what does DNA actually do?
Deoxyribonucleic acid DNA is a nucleic acid that contains the genetic instructions for the development and function of living things. It is often compared to a blueprint, since it contains the instructions to construct other components of the cell, such as proteins and RNA molecules. The DNA segments that carry genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the expression of genetic information.
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