DNA Transcription

Transcription is the synthesis of a strand of RNA from a DNA template. It is the process by which the information in a DNA strand is copied into a molecule of messenger called RNA. DNA stably and safely stores genetic material in the cell nucleic as a reference. Meanwhile, RNA is like a copy from a reference book because it has the same information as DNA but only used for short-term storage and can exit the nucleus. Although the RNA has the similar information, it is not an identical copy of the DNA segment.

Transcription is steered by an enzyme known as RNA polymerase and several accessory proteins known as transcription factors. These factors bind to specific DNA sequences known as enhancer and promoter sequences to recruit RNA polymerase to a suitable transcription site.

Transcription occurs in three stages: initiation, elongation, and termination. Both RNA polymerase and transcription factors form a complex referred to as the transcription initiation complex. The complex starts transcription process, and the RNA polymerase initiates synthesis of RNA by matching complementary bases to a DNA strand. The molecule of the RNA is elongated and after the strand is entirely created, transcription is terminated.

References

http://plato.acadiau.ca/courses/biol/microbiology/Transcription.htm

http://www.nature.com/scitable/definition/transcription-dna-transcription-87

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How Genes are Related to “Baldness”

According to the new study published in United Kingdom, 200 new genetic markers linked with male pattern baldness, which is a great number comparing to the previous study that revealed only eight of the genes. The researchers also found a new mechanism that is efficient in predicting chance of a portion of a population to get a severe hair loss.

In the experiment, the researchers collected baldness linked characteristics from more than 52,000 men ages 40 to 69 years in United Kingdom. Of these men, about 32 percent said they had no hair loss, 23 percent said they had slight hair loss, 27 percent said they had moderate hair loss and 18 percent said they had severe hair loss.

Then, the researchers analyzed the genetic variation known as single-nucleotide polymorphisms (SNPs) of participant’s genome and revealed 287genetic variations, which are located on 100 different genes, that are linked to severe hair loss of men. Most of the variations were located on the genes that are related to formation and growth of hair, and some genes were on the X chromosome that was inherited from their mother.

Based on the result of the experiment, the researchers created a formula that calculates the “genetic risk score” of individuals to have moderate or severe hair loss. However, the researchers note that in the study, information on the age of participants started to loss hair, and if more information were available, it would have been possible to make more accurate prediction of a men’s chance to have severe baldness.

This research has revealed many new information about baldness-linked genes, but it is still hard to make accurate prediction and further researches would be needed to prevent and predict individuals’ hair loss pattern, the researchers noted.

 

reference: http://www.livescience.com/57887-baldness-genetic-markers.html

Why do we SLEEP?

We feel the urge to sleep when waves of tiredness fall upon us that has been accumulated along the day. After a good rest, we can feel the burden of physical and mental fatigue removed from our  body.

Through this, we can emit a question, “Do people sleep to relieve stress?”.

Although this is the significant answer to the question, there are other reasons why sleeping is crucial to our body.

1 Necessary Energy source; Sleep

One way to think about the function of sleep is to compare it to another of our life-sustaining activities: eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow, repair tissues, and function properly.

2 Sleep is crucial for LEARNING

Studying mice, scientists at Johns Hopkins have fortified evidence that a key purpose of sleep is to recalibrate the brain cells responsible for learning and memory so the animals can “solidify” lessons learned and use them when they awaken. Without at least 4~6 hours of sleep, more than 40% of the content one studied are not solid in the recollective systems in one’s brain. For young infants 11~13 hours of sleep is required for this ability to function correctly.

But still, the answer to the question cannot be satisfied with the pre-suggestions, for the question is asking for the fundamental reason why animals started the action, “sleeping”.There are several theories to clarify the reason to this action that existed to all living organisms from birth .

Inactivity Theory

DNA Damage and Mutation

DNA damage is a change in the chemical structure of DNA. It can be a break in a strand of DNA, a chemically changed base like 8-OHdG, or a base missing from the DNA backbone. Natural damage to DNA can result from hydrolytic or metabolic processes. During metabolism, compounds that damage DNA such as reactive oxygen species, reactive carbonyl species, reactive nitrogen species and lipid peroxidation products are released. On the other hand, hydrolysis process weakens chemical bonds in DNA.

Although both DNA damage and mutations are types of error in DNA, they are distinctly different. When a DNA is damaged, its chemical structure is altered. In mutation, alteration occurs in the DNA sequence.

Mutation and DNA damage have different biological consequences. Although many DNA damages are repairable, such repairs are not 100 percent effective. Un-repaired DNA damages mostly accumulate in non-replicating cells (cells in the muscles or brains of adult mammals) and can result in aging. In replicating cells, errors occur during replication. These errors can cause epigenetic alterations or mutations. Both of these alterations can be replicated and eventually passed on to subsequent generations of cells. These alterations can change regulation of gene expression, change gene function and possibly contribute to the development of cancer.

References

http://www.nejm.org/doi/full/10.1056/NEJMra0804615

http://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344

Roles Played by DNA in Cells

DNA is long chain molecule that has a central role in life. The information encoded in DNA strands control organisms’ genetic make-up. The four roles of DNA are encoding information, gene expression, recombination, and replication.

The base sequence of C, G, A, and T along a strand of DNA are organized into units known as genes. A neighboring trio of bases, known as codon, specifies specific amino acids. Thus, base sequence in genes determines the amino acids sequence in proteins. Normally, amino acids are biochemical units of a cell’s function and structure.

Each cell has a full complement of genes. However, cells in different organs and cells behave and look differently. This is because only some DNA in each cell makes proteins. DNA acts as a traffic cop for the protein types a cell will make.

In the evolution of species, DNA plays a major role. Normally, chromosomal DNA doesn’t interact with each other. Nevertheless, through genetic recombination process, sections of different chromosomes exchanges places with each other, resulting in new sequence of genetic material. When such changes take place, new proteins are produced, which can be beneficial to an organism.

During cell division, the chromosomes that contain the DNA strands replicate themselves so that daughter cells get the full set of genetic material. When replicating, DNA double helix unwinds, enabling each strand of DNA to act as a template of a newly created complementary strand that makes a new double helix.

References

http://education.seattlepi.com/four-roles-dna-must-play-cells-4359.html

https://www.ncbi.nlm.nih.gov/books/NBK26821/