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Genetics

What Animals Have Been Cloned?

June 27, 2011 by rfcamat Leave a Comment

Dolly
Dolly, the first mammal to be cloned (Wikimedia Image)
It was in 1996 the world woke up to the news of a sheep named Dolly created through a technique called cloning. Dolly was a carbon copy of another sheep and this started a debate on should scientists be acting like God and producing animals and humans on order.

Cloning is done by removal of DNA from an ovum and replacing it with the DNA of an adult animal. The fertilized ovum is implanted in a womb and an identical or clone animal can be produced. However, the technique is fraught with risks. The cloned animals have been known to carry genetic disorders and have a comparatively short lifespans.

Not many people know that Dolly was not the first animal to have been cloned by scientists. Way back in 1958, scientist John Gurdon claimed to have cloned a frog by using intact nuclei from somatic cells of a Xenopus tadpole. In 1963, Chinese embryologist Tong Dizhou created the first fish clone by inserting the DNA from a male Asian carp into the egg of a female Asian carp. Dizhou went on to create the first interspecies carp clone by inserting Asian carp DNA into a European crucian carp in 1973. In 1986, a mouse named Masha became the first mammal to be cloned using embryo cell.

However, Dolly is still regarded as the most significant achievement in the history of cloning because she was the first mammal to have been cloned using adult cells. Before her, cells extracted from an embryo were being used to create a clone. The success of the Dolly experiment also resulted in a fierce competition among various research groups who started cloning one animal after another.

Scientists at the University of Hawaii created Cumulina, the first mouse clone using adult cells, within one year of Dolly’s birth in 1997.[ad#co-1]

The first cloned calf was also born in the same year and later kept at Minnesota Zoo Education Center. In 1999, Dr Xiangzhong (Jerry) Yang cloned a Holstein heifer named Amy by using ear skin cells from a high-merit cow named Aspen at the University of Connecticut. He followed it up by three additional clones, Betty, Cathy and Daisy in the same year.

The year 1999 saw birth of Second Chance, a Brahman bull which was cloned from a celebrity bull Chance at the Texas A&M University. The research centre was also successful in cloning a Black Angus bull named 86 Squared 15 using cells from his donor, Bull 86, which were frozen in 2000. Just like its parent, the cloned bull also exhibited natural resistance to tuberculosis, brucellosis, and other diseases which can be transmitted to meat.

Five Scottish piglets were created using cloning technique in 2000. In 2001, cloning was done to save Gaur, an endangered species of wild cattle. It was born from a surrogate domestic cow mother at the Trans Ova Genetics in Sioux Center, Iowa, USA. However, the clone died within two days.

The year 2001 saw intensified activity in the field of cloning with birth of two female jersey cows Millie and Emma at the University of Tennessee. They were the first cows to be produced using standard cell-culturing techniques.

In the same year a cat called CopyCat was cloned at Texas A&M University. Though the DNAs of both the clone and the host were same, they had different personalities. Around 10 more Jersey cows were cloned at the University of Tennessee in 2002 while the first commercially cloned cat, Little Nicky, was created by Genetic Savings & Clone in 2004.

In 2003, a Boer goat was cloned at Texas A&M University. In the same year, three male mules were cloned for the first time while a rabbit was also cloned in France.

The year also saw the birth of a first cloned deer named Dewey at Texas A&M University while in 2005 South Korean scientist Hwang Woo-Suk cloned the first dog, Snuppy, an afghan hound. South Korean scientists went on to clone sniffer dogs.

Anatolian Grey bull called Efe was cloned in Turkey along with world’s first buffalo calf through the “hand guided cloning technique” in the year 2009. Next year, the first Spanish fighting bull was cloned by Spanish scientists.

The cloning experiments on animals are still on around the world while there are some unverified claims of human cloning too.[ad#afterpost]

Filed Under: Biology, Genetics

What Causes Widow’s Peak Hair?

June 27, 2011 by rfcamat Leave a Comment

Steven Seagal has a prominent widow's peak hairline
Steven Seagal has a prominent widow's peak hairline (Wikimedia Image)

Leonardo DiCaprio, Keanu Reeves, Steven Seagal and John Travalota, what do they have in common? Besides being handsome Hollywood superstars, all three have similar hairline. The ‘V’ shape at the center of their heads, popularly known as ‘widow’s peak’, gives a unique and mysterious look to these stars. Look around and you will find both men and women with such a pointed hairline.

While many attribute this natural hair style to particular personalities, historical references suggest that a woman with such a hairline will outlive her husband because the shape is identical to a peaked hood worn by women in mourning. This is why the name ‘widow’s peak’.

However, both men and women can have a widow’s peak hairline and no particular trend either related to deaths of their spouses or personality trait has been observed with those possessing it.

It’s only Hollywood which has used the trait to indicate dark inner qualities or evil character. Whether it’s serial killer Hannibal Lecter or Batman’s foe, the Joker, they all have got widow’s peak to signify wickedness. Some actresses, including Marilyn Monroe, Drew Barrymore and Sandra Bullock have also got widow’s peak but this feature of theirs has not been fully exploited.

Genetics of widow’s peak hair

Largely, researchers believe that widow’s peak is linked to genetics. However, even this has been categorized as a myth by another small group of scientists who say that the theory has not been proved in field. But since no further work has been done in this area, not much is known about the real and definite cause.

It is believed that widow’s peak is a classic sign of male-pattern baldness. Men with this disorder have a receding frontline from the corners and hence the front becomes more prominent. The condition progresses with age but even men in their 20s can have widow’s peak.

Men are genetically predisposed to male pattern baldness. The level of dihydrotestosterone or DHT, which is a byproduct of the male hormone testosterone, builds up in their scalps resulting in hair loss. DHT not only blocks nutrients from reaching the hair follicles, it also reduces the size of these follicles resulting in thinning of hair. Hence, follicles keep shrinking and in the end become permanently inactive.

Heredity is the main reason for a person to be predisposed towards baldness and genes from both paternal and maternal sides decide your chances of getting bald. The greater the number of bald people in your ancestry, the greater are the chances of you experiencing hair loss.[ad#co-1]

Possible treatment

Doctors generally use an over-the-counter topical treatment called Minoxidil which can actually help slow the rate of hair loss and also grow new hair in selected cases. Other oral medications may be more effective but have adverse impact on sexual functioning. However, none of the treatment options have long lasting benefits.

Currently, doctors are relying more on hair transplants and other methods of hair improvement rather than medications for greater effect.

Transplant surgery requires removal of hair follicles from back of the head and its transplantation to the areas which has less or no hair. Back-of-head hair follicles are used because it is believed they are not affected by the action of DHT.

The transplanted follicles again sprout healthy hair while the back of the head from where the follicles are retrieved also gets back the normal look on its own.

Genetics of widow’s peak notwithstanding, many don’t consider it as botheration and they flaunt their widow’s peak with elan Who would actually want Leonardo DiCaprio to do away with his widow peak when we know that it lends a unique appeal to his face and personality?[ad#afterpost]

Filed Under: Genetics

Is Tongue Rolling Genetic?

June 27, 2011 by rfcamat Leave a Comment

Tongue rolling
Tongue rolling (Rochelle/Flickr)

Can you roll your tongue into shape of a test tube? Do you get dry ear wax? Do you have cleft chin? Can you wiggle your ears? When you clasp your hands which thumb lands up on the top? These questions may seem innocuous and unwarranted but a whole lot of researchers are scratching their heads on these puzzles which many believe is linked to genetics.

So can you really roll your tongue into shape of a tube? Not many people can but then they do have friends who can and this difference some researchers say is because of genetics. Biology students are taught that tongue rolling is the simplest way to explain inherited genes. Those who can roll their tongues have inherited the gene from their tongue-rolling parents while those who can’t also have parents who can’t roll their tongues. You have got your genes from your parents and even if one of the parents has the tongue-rolling gene, you will be able to roll your tongue.

It’s not so easy to explain

The explanation is not as simple as it is made it out to be and your biology teacher might be wrong after all because there are people who can roll their tongues while their parents can’t. Another research study done by Matlock in 1952 concluded that identical twins don’t always share the tongue-rolling trait. Identical twins are known to have identical DNAs and hence should also share the ability to roll the tongue if they have same genes.  In 1975, another researcher demonstrated that identical twins are no more likely to share tongue-rolling than are fraternal twins. This gives birth to the idea that environment is also a major factor. Both the twins might be having the gene but it is not expressed in one of them due to absence of an environmental trigger.

The environmental trigger theory has also found takers in several other conditions like autoimmune disorders. People are known to be predisposed to them but these disorders are manifested in only those who encounter particular environmental triggers stress, pollution or specific disorders.[ad#co-1]

Another theory regarding tongue rolling is that there might be another gene called modifier gene which is controlling the expression of tongue rolling gene. So there can be parents who possess the gene to roll their tongues but still they can’t roll them because the modifier gene in them is off. Now their child can have the ability to roll the tongue if they modifier gene is not passed on.

All these explanations may seem confusing but that’s not the end of the whole story. Tomorrow some new research may prove that all the above propositions are wrong and there is some new factor that defines tongue rolling. Meanwhile, surveys done by biologists have put forth interesting data related to tongue rolling. It was found that in Spain 67 per cent of females can roll their tongues compared to just 64 per cent of the male population. However, Spanish men are better at wiggling their ears. Around 20 per cent of them can wiggle their ears as compared to 10 per cent of women. Another Iranian researcher found that north England does not have many people who can roll their tongues and this, he believes, is because of genetic intermingling with the Scandinavians.

Whatever the final verdict be, it’s clear that if you can roll your tongue, genetics are involved in this ability of yours. However, to what extent the power of genetics works in this scenario is not yet known. So, the picture is out but the contours are still being finalized.[ad#afterpost]

Filed Under: Biology, Genetics

Polydactyly: Causes, Symptoms and Treatments

June 21, 2011 by rfcamat Leave a Comment

Polydactyly

Left hand of African woman with postaxial polydactyly.
Left hand of African woman with postaxial polydactyly (Wikimedia Commons Image)

Polydactyly is a congenital physical aberration in which a person has more than five fingers on his/her hand or if his/her foot has more that five toes each. The term is derived from the Greek words ‘polus’ which means ‘many’ and ‘daktulos’ which means ‘fingers’. The extra digit on either hand or toe may be rudimentary or fully formed with or without bones at all. For rudimentary polydactyly, the extra finger or toe is usually a piece of soft tissue. In rare cases, the extra digit may develop fully and become a functional finger or toe.

Polydactyly is one of the most prevalent inborn hand abnormalities which manifests in 1 out of 500 live births. Experts formed a classification for this congenital condition based on its extent and location. Fully formed digits having a complete number of bones and joints are classified as Type A polydactyly while rudimentary fingers or toes are classified as Type B polydactyly. Based on location, polydactyly can be preaxial, central or postaxial. Preaxial when the extra digit occurs near the thumb or big toe; postaxial when it is located near the pinky or near the smallest digit of the foot; and central when the extra digit arises between the  biggest and smallest digits of the limbs. Among Asians, an extra thumb is most likely to arise (preaxial polydactyly) while an extra finger on the small digit side is most common among African-Americans (postaxial polydactyly). Polydactyly may occur as an isolated condition or it may be expressed as a result of an underlying health condition such as Meckel syndrome, trisomy 13  and Grebe type Chondrodysplasia. In most cases however, polydactyly is caused by genetic factors.

Genetic Causes of Polydactyly

The gene that codes for polydactyly is found on one of the short legs of chromosome seven and has an autosomal dominant mode of inheritance. Since it is autosomal, its occurrence among males and females is equal. And because it follows a dominant pattern of inheritance, a child with a polydactyl parent has at least 50% possibility to inherit and show the trait.

One of the genes behind polydactyly is GLI3. It serves its function by providing instructions for making a protein (GLI3 protein) that has the capacity to turn on or to turn off gene expression. During embryonic development, GLI3 protein plays a key role in shaping tissues and organs by interacting with other genes. When a mutation or a change related to the GLI3 gene in chromosome seven occurs, deletion or rearrangement of genetic materials for example, limb development becomes severely affected which can lead to polydactyly at birth.

Another gene that can cause polydactyly is the LMBR1 gene which is also located in chromosome seven. Similar to the case of GLI3 gene, a disruption in the LMBR1 region can alter the expression of a protein called Sonic hedgehog homolog (SHH) which regulates vertebrate organogenesis and growth of digits. Defects in this gene are associated with preaxial polydactyly while abnormalities in GLI3 gene are associated with both preaxial and postaxial polydactyly.[ad#co-1]

Diagnosis

Physical examination after birth is the easiest way to diagnose polydactyly. Diagnosis can also be done before childbirth by looking at family histories and by performing several prenatal tests. One of the most commonly used method during pregnancy is a prenatal ultrasound called a sonogram. If polydactyly is seen in the ultrasound, other medical tests may be conducted to determine if the condition is associated with other genetic disorders. In cases where the result of a sonogram becomes unyielding, a method called embryoscopy is also employed. This test involves the the direct visualization of the embryo by inserting a fiber optic scope through the mother’s abdominal wall and uterus. For a more genetic approach and reliable result, amniocentesis is performed. This requires the analysis of amniotic fluid sampled from the mother’s womb primarily to detect chromosomal abnormalities in the fetus.

Treatment

Treatment for polydactyly depends on the severity of the disorder. X-ray is usually done to determine the extent of polydactyly so as to apply the corresponding treatment for such condition. For isolated cases where no major health consequences are likely to arise, surgery is used to remove the extra digit. For Type B polydactyly, the extra finger or toe can be surgically removed before the newborn is discharged from the hospital. Type A polydactyly on the other hand is more complicated and requires more surgeries compared to the other type and is usually corrected when the child is above one year of age.[ad#afterpost]

References

  • http://www.nlm.nih.gov/medlineplus/ency/article/003176.htm
  • http://www.umm.edu/ency/article/003176.htm
  • http://www.healthline.com/galecontent/polydactyly
  • http://www.childrenshospital.org/az/Site1073/mainpageS1073P1.html
  • http://ghr.nlm.nih.gov/condition/greig-cephalopolysyndactyly-syndrome
  • http://www.brighthub.com/science/genetics/articles/47390.aspx
  • http://answers.yourdictionary.com/medical/what-causes-polydactyly.html
  • http://www.springerlink.com/content/d2t10p466rm502kt/

 

Filed Under: Genetics, Medicine

Ethical Issues Associated With Human Cloning

June 18, 2011 by rfcamat Leave a Comment

Dolly's remains are exhibited at the Museum of Scotland.
Dolly's remains are exhibited at the Museum of Scotland. (Wikimedia Image)

In the movie “The Sixth Day”, a clone of Adam Gibson (Arnold Schwarzenegger) takes over his family and professional role forcing the original character to prove his authenticity in the year 2015.

The movie could not be far from reality especially when experiments to produce human clones are being done clandestinely across the globe.

Cloning debate gained momentum since Dolly, the first cloned mammal, walked over the earth in 1996. The birth of Dolly opened the possibility that humans can be also be cloned using the same technique. Today, scientific cloning is yet to go mainstream mainly because it’s a difficult and expensive procedure and till now the clones produced have not been able to live long enough.

While animal cloning is quite acceptable in the society, we are yet to accept the fact that some time in future human clones will be greeting us in neighborhood parks.

Human cloning is possible through various methods. Embryo cloning, one of the methods, involves production of identical twins artificially. A few cells extracted from a fertilized embryo can be induced to develop into a duplicate embryo having DNA identical to its parent embryo. This technique has been used successfully on animals.

Another method is through removal of DNA from an ovum and replacing it with the DNA of an adult. The fertilized ovum is implanted in a womb and an identical or human clone can be produced. However, studies done on animals show that this technique can result in severe genetic defects in the newborn. Due to these side effects, this technique is banned in several countries but an Italian embryologist claimed to have developed a human clone through this procedure.

Several ethical issues of human cloning crop up through the years. Some people would like to have a clone to have a biological insurance to extract organs from in case their original ones fail or damaged. In this scenario, the existence of a clone just to save the original human being or to act as a replacement for him strongly questions human morality.

While a human clone’s right to identity is jeopardized, questions are raised on his right to inheritance, choice of a life partner, and other crucial life matters.

The safety of cloned humans is also questioned. While most attempts to clone mammals have failed, several of the clones born suffer from debilitating conditions and die prematurely. Moreover, we still don’t know how cloning impacts the brain and other vital organs in the body.

Therapeutic cloning, another technique, differs from reproductive cloning in a way that no offspring is given birth to. Only stem cells are extracted from the pre-embryo for the purpose of developing organs or tissues that can replace the damaged organs of the original DNA donor. The process eliminates the need to wait for the right donor and since the DNA is exactly the same, there are no complications in organ transplantation..

However, many decry such a procedure since the human embryo is destroyed in the extraction of stem cells. They feel that since embryo is equivalent to a human being, he should have rights equal to those of normal humans and killing him just to save the life of another person is simply unjust.

The stem cell proponents, however, claim that the stage at which the stem cells are being extracted is a very nascent stage and the embryo does not have brain to have awareness of the self and also lacks a thought process. They feel it can only be termed as human when it’s aware of the environment and has sensory capabilities, organs and limbs.

Time will tell whether humans are going to accept human cloning technology or not. But many scientists are unstoppable in developing perfect techniques on human cloning and stem cell production.


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Filed Under: Biology, Genetics

The Advantages and Disadvantages of Genetically Modified Food

June 18, 2011 by rfcamat Leave a Comment

Btcornafrica
Kenyans examining insect-resistant transgenic Bt corn (Wikimedia Commons)

There is no love more sincere than the love for food. Food is  a uniting factor among different cultures since everybody likes to taste and enjoy exotic cuisines from around the world. This is also one of the reasons why the issue of genetically modified (GM) food is generating intense debate because we are what we eat. GM food includes crops, fruits and vegetables which are created by combining quality genes of various species and hence have better nutritional and productive value. The difference between this technique and traditional breeding is that latter occurs only between related species and hence is safe whereas there is no final word on safety of mixing genes of unrelated species.

Both sides of GM food debate are equally vociferous in expressing their opinions. While the pro lobby talks about how the GM crop can give a larger and better yield even in inhabitable conditions, the critics talk about risk to health and environment due to genetic alterations and exploitation of the poor by food corporates. Here we have a deeper look at the issue.

Advantages of Genetically Modified Food

Supporters of GM food crops are mostly relying on scientific data claiming that these crops yield much larger quantity and hence can be the solution to the problem of world hunger. The ability of GM crops to be cultivated even in areas with poor soil and harsh weather conditions is one of the advantages of genetically modified food. Another plus point is that the food produced is higher in nutritional value and can also taste better than the traditional variety. GM crops have inbuilt resistance against pests, insects and diseases allowing them to produce higher yield. The proponents are also claiming that genetic modification can even make certain food free of common allergies. This can be done by removing the genes that express the allergens or substances that trigger allergic reactions.

The GM foods are also capable of staying ripe for long hence there is lesser problem of spoilage. This can be done by adding a gene in the crop that expresses an organic compound that will extend the shelf life of the food.

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Disadvantages of Genetically Modified Food

While the pros of GM food may seem rewarding, the critics claim that they don’t hold water. First of all, they counter the technique itself by putting forth the argument that scientists still don’t know much about the genetics GM crops. They may identify quality genes but where to introduce them so as not to disturb the natural expression is still unclear. In fact, this lack of knowledge can lead to faulty interventions and irrepressible side effects. Traditional breeding has natural checks and balances due to breeding between related species but these are missing in GM food crops.

The hope that GM food can be an answer to the world hunger is another faux pause because they claim that millions of people sleep with empty stomach not because of lack of food but because of improper distribution. Millions of tons of food are wasted every month around the world because they do not reach the needy. Financial, infrastructural and political reasons rather than less production are responsible for the large number of hungry people across the globe.

The GM food may be having inbuilt resistance to common pests and insects but these organisms are known to mutate according to changes in their environment for survival. Thus, disease-resistant crops will only give rise to superbugs which will be more difficult to destroy.

Another big issue with GM crops is that they cross-pollinate with nearby normal crops and lead to ecological issues. Furthermore, if GM crops contain vaccines and antibiotics, human health is in peril as it would contribute to the development of resistance genes to human viruses and bacteria that we normally kill using vaccines and antibiotics.

Opponents assert that GM crops are patented by big biotechnology corporations that make sure that the harvested grains/fruits are not viable source of seeds to force farmers to buy costly seeds every time they want to cultivate the land.

Tests to validate the risks of GM crops are very expensive that most corporations avoid testing each and every food item. This increases the chances of unsafe food getting served to people.

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Filed Under: Biology, Genetics

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