DNA is also known as deoxyribonucleic acid, it is an important molecule for life. DNA holds instructions telling our bodies how to develop and function. An important property of DNA is that it can replicate, or make copies of itself. Most DNA is located in the cell nucleus , but a small amount of DNA can also be found in the mitochondria. DNA is a long thin molecule which is made up of nucleotides. There are 4 types of nucleotides: adenine, thymine, cytosine, and guanine. Each chromosomes is made up of DNA, which is how we get genes.

An image of a DNA

Structure of a DNA

DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C). The order of these bases is what determines DNA's instructions, or genetic code. The order of nitrogen bases in a DNA sequence forms genes, which in the language of the cell, tells cells how to make proteins. The entire human genome contains about 3 billion bases and about 20,000 genes. Nucleotides are attached together to form two long strands that spiral to create a structure called a double helix. The double helix structure looks like a ladder. The bases on one strand pair with the bases on another strand: adenine pairs with thymine, and guanine pairs with cytosine. DNA molecules are known to be very long. DNA is packed tightly to form structures that are known as chromosomes. Every chromosomes contains a single DNA molecule. Us humans have 23 pairs of chromosomes. Chromosomes are found in the cell's nucleus.

Replication of DNA

DNA has all the details for developing all of the cell's proteins. When the cell reproduces, it gives all of the details to the daughter cells. Before a cell can reproduce, it has to replicate or make another copy of the DNA. When the DNA replication occurs it depends on the the cell, whether it is a prokaryote which does not have a nucleus or a eukaryote that does have a nucleus. DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes.

Replication of DNA: Preparation - step 1: Replication Fork Formation

Before DNA can be replicated, the double stranded molecule must be “unzipped” into two single strands. DNA has 4 types of nitrogen base called adenine (A), thymine (T), cytosine (C) and guanine (G) that makes pairs between the two strands. Adenine only pairs with thymine and cytosine only binds with guanine. For the DNA to unwind, the base pairs must be broken. This is accomplished by the enzyme known as the DNA helicase. The helicase breaks apart the bonding between the pairs to separate the strand which is known as the replication fork.

Replication of DNA: Replication - step 2: Primer Binding

When the DNA has separated, a small piece of RNA called a primer always binds as the starting point.

Replication of DNA: Replication - step 3: Elongation

Enzymes also known as DNA polymerases are in charge of creating the new strand by a process called elongation. The strands begin replication by binding with several primers. Every primer is only a number of bases apart. Enzymes then adds chunks of DNA, called Okazaki fragments to the strand in between primers. is process of replication is discontinuous as the newly created fragments are disjointed.

Replication of DNA: Replication - step 4: Termination

When both of the continuous and discontinuous strands are built, an enzyme called exonuclease removes all RNA primers from the original strands. These primers are then replaced with appropriate bases. Another exonuclease looks over to see the newly formed DNA to check, remove and replace any errors. Another enzyme called DNA ligase joins Okazaki fragments together developing a single unified strand. In the end, replication produces two DNA molecules, each with one strand from the parent molecule and one new strand.

Replication of a DNA

What is DNA Screening?

DNA screening (genetic testing or genetic screening) is a genre of medical test which shows the differentiate in chromosomes, genes, or proteins. Your DNA contains information about your heritage, and can sometimes reveal whether you're at risk for certain diseases. When the lab workers do gene tests, they mostly look for "abnormalities" in the DNA which is taken from an individual's blood, body fluid or tissues. DNA tests, or genetic tests, are used for a variety of reasons, including to diagnose genetic disorders, to determine whether a person is a carrier of a genetic mutation that they could pass on to their children, and to examine whether a person is at risk for a genetic disease. For an example, the mutations in the BRCA1 and BRCA2 genes have shown the high risk of breast and ovarian cancer, and from the DNA testing it can reveal whether the person has these mutation. The tests can also search for a massive mistake such as a gene that has a component missing or a component that has been added. Others look for minor changes within the DNA. Other mistakes that can be found include genes that are too active or those that are lost entirely. There are many methods of DNA screening such as:

1. blood test

2. bone sample

3. stool sample

4. hair

5. dead skin

6. nail sample

7. bottled fluids (mucus, blood, urine and sweat)

BRCA1 and BRCA2 are genes that are tumor suppressor genes.

Different Technology Used for DNA Screening

Thermal cycler also known as PCR machine, thermocycler, or DNA amplifier is a laboratory apparatus is used to amplify a portion of the DNA from the polymerase chain reaction (PCR).

Fluorescence in situ hybridization also known as FISH is used to detect and localize the presence or the absence of detailed DNA sequence on chromosomes. FISH is mostly used for finding certain features in DNA for use in genetic counselling, medicine, and species identification.

Southern blot is a method used to detect a specific DNA sequence in DNA samples. Southern blot analysis reveals information about DNA identify, size, and abundance.

What can you get from the results?

After the genealogist looks over the test results, they can find certain results from the tests which are:

• who your parents are

• who your ancestry's are

• there is genetic testing for background

• to see if there are an genetic diseases

The Individual's Right to Choose

DNA tests most commonly present an opportunity for individuals to become informed about their genetic predisposition to disease, and for them to be aware of what problems they might face. Most people in life have certain diseases such as thalassaemia, for which there is no cure and it limits the individual's freedom of choice. Respecting a patient’s confidentiality by not disclosing the results of a genetic test to third parties can therefore conflict with the well-being of family members, who could benefit from this knowledge. Genetic test results can have implications for a person's health, and the tests are often provided along with genetic counseling to help individuals understand the results and consequences of the test.

Negative and Positive Economic impact

In a lot of countries genetic services are either needed, and in some stages they are developed or still developing. The quality and availability of genetic technologies alters between high-income countries to low to middle income countries. In different countries such as the United States, Canada, Australia, United Kingdom, and more European countries, genetic technologies are strongly established, advanced and universal. Presently it is imbalanced in affordability of genetic services between low-to middle-income countries is a cause of concern for the prominent international organizations that are centred around public health and development concerns. Particular technologies include carrier identification screening, prenatal diagnosis, new born screening, and reproductive technologies. In several high-income countries, genetic services that are provided in variety of settings including community clinics, academic health centres, public health departments, and private practice still need enhanced systems of assessment. Genetics laboratories are scarce and DNA-based diagnosis, which can be inexpensive, is available in only a few centres in low-income countries. The cost of the genetic technology is just too much for some countries which cause a lot of severe problem for most individuals. which causes Lack of information on genomics and health financing options, are some barriers among many, that also affect the use of genetic services among populations in both high income and low- to middle-income countries. Health policy can also play an important role in the expansion of genetic services that can be made more accessible and affordable for the public.

Negative and Positive Social Impact of DNA Screening

There are several disadvantages which any individual considering undergoing testing should be aware of (these include the limitations of the genetic testing technique). genetic alterations generally need to be identified in a family member who has already developed cancer this can lead to distress and difficult family relations, for example if there are no surviving family members who are able to undergo diagnostic genetic testing, or if an individual is reluctant to undergo testing he/she may be subject to pressure from other family members. A positive genetic test can also lead to an increased level of anxiety and individuals may feel guilty for having potentially passed a gene alteration on to their children. There may also be issues for individuals wishing to obtain health and life insurance. A lot of family's have had issues and a lot of individuals have committed suicide. Receiving a negative genetic test can also affect family relations, with many individuals feeling ‘survivor guilt’, for example if they have a brother or sister who has been shown to carry that gene alteration, they may feel guilty at having escaped the increased cancer risk, while their sibling is still at risk.

There are many potential benefits that can arise as a result of genetic testing. Individuals who don't carry harmful gene alteration which is known to run in their family may feel that they are less anxious and have a better quality of life; they may also benefit from the knowledge that they have not passed a gene alteration on to their children. Plus, such individuals do not require the exact same check ups as do people who have the disease (genes). Also the patients will have knowledge about their own body and will have a more social life with their families as well as with the doctor which is positive in some cases.

Environmental Impact

Genetic modification has a huge impact on the environment. Genetic modification operates on the premise that a desired gene from one organism can be inserted into a recipient organism that normally does not have that gene. When GM crops are grown, there is the potential for genes to be transferred to other organisms in the environment. This creates the possibility of uncontrolled growth, which could be a real threat if any unexpected and dangerous consequences arose from the gene transfer. If a transfer of genes did occur, the resulting species may not survive at all because the traits would not be beneficial in that particular environment. Another aspect to consider is that GM technology may itself evolve to allow techniques to prevent gene transfer from one crop to another. Other effects are considered positive such as reduced need for pesticides and herbicides. It has, however, been argued that resistance may eventually occur so any benefit would be short-lived. Farmers also benefit from reduced costs when GM crops that are engineered to be herbicide and pesticide resistant are used. The reduced use of pesticides also holds an additional benefit of reducing toxins released into the environment.

Genetic Modification. Inserting genes into a tomatoe

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Created with images by Caroline Davis2010 - "DNA" • Sophieja23 - "woman question mark person" • frolicsomepl - "blood medical attempts" • Candace Nast - "Hair" • agnte - "deadskin foot 1" • nightrose - "French Nails" • White77 - "family holiday people" • PublicDomainPictures - "allergy cold disease" • no3rdw - "All Rights Reserved*" • DonkeyHotey - "Dollar Sign in Space - Illustration" • sarcifilippo - "elderly corridor doctor" • artursfoto - "modified tomato genetically"

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