DNA Transcription

DNA Transcription

Deoxyribonucleic acid, in short DNA, is the genetic material of all living organisms (except in some prokaryotes). The main function of DNA is to store genetic information, responsible for the construction and development of all cells. A stretch of DNA is called a gene and many genes makeup a structure called chromosome. Genes contain the hereditary information of an individual and are responsible for the phenotypic (physical or external) characters and genotypic make-up. Genetic diseases are caused due to passing of certain abnormal genes from the parents to the offspring. A specific set of chromosomes are present in a living organism, for example, human chromosomes are 46 in number.

DNA is a nucleic acid, consisting of two strands of polynucleotides. In a DNA structure, the two nucleotide strands are arranged in an anti-parallel manner, in which they run in opposite directions. The nucleotides are made up of base molecules, sugar molecules and phosphate groups. The sugars and phosphates are joined by phosphodiester bonds and in each of the sugar molecules, a base molecule is attached. DNA present in the nucleus of a cell is called nDNA or simply DNA; whereas, DNA located in the mitochondria of a cell is referred to as mitochondrial DNA or mtDNA. Let's take a look at eukaryotic DNA transcription for expression of genes.

DNA Transcription: A Brief Explanation

While controlling cellular activity, DNA undergoes coding for synthesis of enzymes and proteins. In the process of protein synthesis, the DNA molecules are not converted directly to proteins, but they are transcribed first as mRNA (messenger RNA), which is then translated to proteins. In genetics, the whole process of converting DNA to mRNA to protein is known as central dogma. The first step of transcribing DNA nucleotide to mRNA is known as DNA transcription. Let's discuss in brief about the transcription of nDNA.

In DNA transcription, specific enzymes called RNA polymerases and other proteins play a major role. There are specific nucleotide sequences in the DNA strand, which act as start and stop point. In the initiation phase, RNA polymerase enzyme attaches to a specific 'promoter region' in one of the DNA strand. With this signal, the double helix structure of DNA unwinds, allowing the RNA polymerase to transcribe the DNA strand to which it attaches.

During the transcription process, the RNA polymerase synthesizes single-stranded mRNA polymer under the direction of the specific DNA strand, which acts as template. The RNA polymerase moves along the DNA strand (in 3′ → 5′ direction) and continues to elongate mRNA polymer, until it reaches a specific 'terminator region' in the DNA strand. As soon as the RNA polymerase reaches this particular nucleotide sequence, it detaches itself from the DNA strand. At the same time, the mRNA polymer (or transcript ) is released into the nucleus where the DNA transcription takes place. Thus, DNA transcription is completed.

The mRNA polymer that results from DNA transcription undergoes modification in the nucleus, after which they move to the cytoplasm for translation process. In the cytoplasm, the mRNA polymers with the help of ribosomes and other enzymes synthesize proteins. This way, DNA transcription and translation work together for protein synthesis, which is very essential for gene expression. In fact, the characteristics are expressed by genes via the proteins that they code for. With this understanding, DNA researches are ongoing to solve the mystery of certain genetic diseases and disorders.

Genetic Predisposition

Genetic Predisposition

Genetic predisposition, also called genetic susceptibility, is defined as the effect of gene that influences the phenotype expression of an individual, including the susceptibility to certain diseases and disorders. As we already know, genetic composition is directly responsible for the physical attributes of an organism. Unlike this genotypic effect, the affectation of genetic predisposition can be altered or changed with respect to environmental factors. In contrary to this, environmental predisposition refers to influencing the phenotype by external conditions.

Genetic Predisposition: Explained

In medical science, genetic predisposition is evaluated to correlate the possibility of diseases developing in an individual and disposition of the genes to the particular health problems. Like for instance, an individual having a predisposition for schizophrenia has an increased risk of manifesting this psychotic disorder than the general population. However, it doesn't mean that he or she will surely get the condition. The main approach used for identifying genetic predisposition is none other than genetic testing and screening. For your understanding, genetic predisposition of various cases are highlighted below:

Genetic Predisposition to Obesity
Go through the probable causes of obesity and you will come across genetic predisposition as one of the factors responsible along with diet and lifestyle habits. In a study conducted in Boston University Medical School, it is found that a slight alteration in the gene (INSIG2) is the primary reason for obese propensity. As this particular gene undergoes changes, it affects fat production in the body, thereby increasing the risk of becoming overweight or obese. Similar to this, some people are genetically predisposed to remain slim.

Genetic Predisposition to Addiction
It is suggested that approximately 50 percent cases of alcohol addiction are caused due to genetic predisposition to alcoholism. The remaining 50 percent are because of poor coping skills. Keeping it in statistical terms, the offspring of drug addicts are eight times more prone to become addicted than others. Supporting this statement, Dr. Nora Volkow, the director of national institute on drug abuse (NIDA), claimed that some individuals are genetically predisposed to addiction.

Genetic Predisposition to Depression
When it comes to treatment of major depression problems, the option lies in identifying the underlying causes and preventing them. But, the main query that lingers in the minds of physician is the genetic basis of depression. A genetic research of identical twins concluded that if one of them is depressed, the other person has 50 percent chances of getting depressed. No doubt, the gene responsible for triggering depression symptoms is identified. But, it differs from one report to another. Thus, it is still not clear as to which gene leads to depression.

Genetic Predisposition to Disease
Apart from genetic disorders, genetic predisposition to cancer, diabetes and osteoarthritis have been studied on a global scale. It is found that a person having a medical history of diabetes, either in first-degree relative (parents or siblings) or second-degree relative (uncle, aunt, cousins) is more likely to develop this blood sugar problem than others. Likewise, an individual with a genetic predisposition to lung cancer should refrain from smoking to reduce risk of developing lung carcinoma in the later stages of life.

According to scientists, genetic predisposition has both positive and negative effects. The good point is inheritance of intelligence, strong mental ability and specific talents from parents to their offspring. Whereas, tendency to develop mental disorders and medical conditions is the downside story of genetic disposition. In the concluding note, studying human genetics and identifying disposition towards a disease will surely help an individual in minimizing the risk of developing it in future.

Chromosomes in Humans

Chromosomes in Humans

The correct diploid number of chromosomes in humans is 46, out of which 44 are somatic ones and remaining 2 are sex determining chromosomes. Any abnormalities in the chromosomal number or structure are expressed as genetic disorders. Read on to know more...

Chromosomes are threadlike structures of DNA present in the cell nucleus, which are responsible for carrying genetic information. The word chromosome is derived from the Greek words for color (chroma) and body (soma). In laboratory studies, chromosomes are stained easily with specific dyes, hence the name. Studying chromosomes in humans is an important aspect in genetics, as the phenotypic expression of an individual entirely depends on them. Also, genetic disorders are caused due to abnormalities in the chromosomes.

Chromosomes in Humans: An overview

The human genome is diploid, meaning it contains 2 sets of chromosomes. As per researches in human genetics, it is found that more than 3 billion DNA base pairs are present in a single haploid human genome. In addition to these, chromosomes contain non-coding genes, regulatory elements and proteins. Together, they are arranged in an organized manner as chromosomes. Following are some points concerning facts about human chromosomes, which you may find interesting.

Number of Chromosomes in Humans
The total chromosomes can be expressed in diploid and haploid number. While the diploid number of chromosomes in humans is 46, the haploid number is 23. All normal human cells are diploid and the gametic cells (male gametes and female gametes) are haploid. In short, the number of chromosomes in humans differs, based on whether you are referring to a diploid cell or a haploid cell.

Sex Chromosomes in Humans
When we say sex chromosomes, they are used for determining the gender of an individual. Out of the 23 pairs of chromosomes, 22 are autosomal and 1 pair is the pair known as sex chromosomes. Males have one 'X' and one 'Y' chromosome, represented as (XY); whereas females have two copies of the same chromosome 'X' (represented as XX). Besides humans, this XY sex-determination system is observed in many sexually reproducing organisms, like ginkgo biloba tree and Drosophila insect.

Chromosomes and Reproduction
In the process of fertilization, the male gamete that contains 22 autosomes and 1 sex chromosome (either X or Y) fuses with the female gamete that contains 22 autosomes and 1 sex chromosome (X) to form a diploid zygote. Thus, the resulting zygote has 44 autosomes and 2 sex chromosomes (may be XX or XY). Precisely speaking, two haploid cells or gametes fertilize to form a diploid cell during the reproduction process, thus retaining the typical chromosome number in humans.

Chromosome Abnormalities in Humans
Abnormalities in chromosomes are usually due to alterations in the chromosome number or structure. An example of genetic disorder due to extra chromosomes in humans is Down syndrome. In this condition, three copies of one chromosome is present in an individual, a condition known as trisomy. On the other hand, lack of one chromosome leads to an abnormality called monosomy. An example of this is Turner syndrome, a disease in females in which there is only one X chromosome.

Speaking about structural abnormalities of chromosomes in humans, they are caused either due to the presence of additional chromosomal parts (duplication) or lack of the same (deletion). In some conditions, sections of the chromosomes get exchanged between two chromosomes during cell division (translocation), resulting in a structural abnormality. In majority of the cases, abnormalities in the chromosomes of an offspring are inherited from its biological parents.

On a concluding note, presence of typical number of chromosomes in humans is imperative to express normal phenotype characteristics. Any major changes in the numerical value or structure is a cause for medical condition. For ease in studies, similar looking chromosome pairs are lined up in a proper fashion, along with their respective numbers, which is referred to as karyotype. Various researches in human genetics are ongoing to find out the solutions for chromosome related medical conditions.

What Makes up DNA

What Makes up DNA


DNA or deoxyribonucleic acid is known as the building block of life. Through this article let us discuss what makes up DNA and its role in life.

Every living being is made up of millions of microscopic structures known as cells. These cells contain various organelles which have an individual function. Among the organelles in the cell, the cell nucleus is the most important since it contains DNA or deoxyribonucleic acid. We are all familiar with the term DNA and have heard it many times. But what exactly is DNA? What makes up DNA and why is DNA important are a few questions many ask. The interesting fact about DNA and RNA is that both are composed of the same material and are polymers of adenosine triphosphate (ATP). Let us take a look at the composition and history of DNA, which is considered to be the storehouse for genetic traits.

What is Deoxyribonucleic Acid?

DNA, which is also known as deoxyribonucleic acid in medical terms, is a nucleic acid which is present in the cell nucleus of all living things. DNA is also known as the 'building block of life' since it holds genetic information about the previous generation which is passed on to the next. This is the reason why DNA is sometimes referred to as a blueprint. Apart from maintaining genetic information of the parent, DNA also plays a major role in many important functions of life.

The DNA molecule is composed of sugar and phosphate molecules, which form a polymer of nucleotides in DNA. This chain of nucleotides is what makes up DNA. The sugar molecules which form the four bases of DNA, adenine, cytosine, guanine and thymine, are essential for the DNA replication process. The two polynucleotide strands are intertwined with each other and form complementary pairs of the bases through the process of hydrogen bonding. The phosphate and sugar groups that bond the nucleotides are sometimes called the backbone of the DNA helix structure. The cell contains chromosomes, which hold the strands of DNA and genes which are attached to it. There are 23 pairs of human chromosomes (or 46 chromosomes) in the body, which control various factors. The genes hold the genetic code like the color of the eyes, body structure and hair color etc.

The DNA research was first carried out in the year 1889, when a well-known Swiss physician and biologist Friedrich Miescher stumbled upon the presence of this nucleic acid during one of his researches. It was this eminent researcher who discovered DNA, which he called 'nuclein'. Later, two other well-known scientists, William Astbury and Phoebus Levene, researched on the structure and the constituents of DNA. In the year 1953, two other biologists James Watson and Franklin Crick, with the help of Rosalind Franklin conducted a detailed study and discovered that the human DNA consisted of two strands interlocked with each other and formed a double helix model. This model was named as the Watson Crick model of DNA in honor of these scientists. The discovery of DNA proved helpful to the field of genetics as it helped in the study of human behavior and also about some rare hereditary diseases.

The DNA also replicates and undergoes transcription. In the DNA transcription process, a DNA structure undergoes protein synthesis and is converted in messenger RNA (mRNA). These messenger RNA are then transcribed into protein molecules. This process leads to gene expression, in which a gene is synthesized to obtain codes. The study of these codes help the researchers in unveiling the mystery surrounding the occurrence of some of the genetic disorders and diseases and to find a cure for them.

There is also another type of DNA, known as mitochondrial DNA, which is present in the mitochondria of a cell. When DNA undergoes mutation and produced mutagens (or defective genes) it can cause numerous health problems which are generally congenital or present at the time of birth. These mutagens can also be transferred from one generation to another. Hope you found this article on what makes up DNA informative.

A new restored gene therapy?

As holographic in one of the previous posts, treating neurodegenerative diseases with RNAi is writer herculean than treating hepatitis C or remaining correspondent diseases. Notwithstanding, a new ponder on the neurodegenerative disease Machado-Joseph, shows that an landscaped sequence therapy is beingness reliable.
What is Machado-Joseph disease and why is it alpha?
Uncovering a aid for Machado-Joseph disease is serious because at acquaint it is untreatable. The disease is defined by degressive locomote discoordination that could, yet, lead to alteration.
The MJD1 cistron is accountable for the creation of ataxin-3 ---a mentality catalyst alleged to be efficacious in the wipeout of venomous proteins in the brainpower. Nevertheless, the mutated MJD1 cistron is not able to food functional ataxin-3 catalyst. The mutated ataxin-3 catalyst then accumulates in the wit and causes neuronal wrongdoing.
This search conducted by Alves, Almeida, Déglon et al. from the Lineman for Neurosciences & Room Assemblage at the University of Coimbra, Portugal and the Make of Molecular Imaging and Molecular Imagery Investigate Halfway in Orsay, France hump plant an landscaped way to quiet the MJD1 mutated sequence and potentially broach Machado-Joseph disease.
Withal, how exactly is this different from any another studies? Change tho' the take relieve uses RNAi to quiet the factor, these researchers bonk restored their targeting precision. Cite, that there are unremarkably two copies of a gene--- the mutated and the regular factor. Thus, if exclusive one gene is mutated and the opposite MJD1 factor is comfort producing formula ataxin-3, it would be deleterious to silence both the mutated and sane MJD1 factor.
The landscaped RNAi has been tried on pussy rats with the neurodegenerative disease. The reflection showed that the RNAi led to a alteration of roughly 50% of the mutated proteins accumulated in the wit of a charged physical.
Nevertheless, we must maintain in noesis that level tho' these results are promising, they are auspicious in rats. Further search has to be through before billowing to clinical trials. On the glaring sidelong, the RNAi handling did not crusade any side effects in the reliable rats; therefore, diminuendo the conception of having sedate back effects in humans. In section, this experiment provides wish that one day RNAi module be old to provide neurodegenerative diseases by silencing the mutated factor and not the mean factor that can solace be effective