Conjoined twins

And after Identical of fraternal twins post, let's go deeper to one of the most intriguing malformations in human beings: the conjoined twins.

The conjoined twins, also known as Siamese twins, are identical twins joined In utero (in the womb). It happens in 1 of 200.000 newborns, mostly in women (75%) and their survival rate is between 5% and 25%.

The name of Siamese twins comes from Chang and Eng Bunker, Thai brothers born in Siam (now Thailand). They travelled with P.T.Barnum circus, and they were joined by a band of flesh, cartilage and their fused livers at the torso. They were not only showed as "monsters", but also as good skilled acrobats and magicians, as well as good in business matters.

Chang and Eng Bunker. Picture from fineartamerica.com

Now we know what conjoined twins are, why does it happen?

Identical or fraternal twins?

They are so similar... but are they really the same? Today we are going to speak about the difference between identical and fraternal twins.

First of all, a twin is one of two offspring in the same pregnancy. The main difference between identical and fraternal twins is that identical twins come from the same zygote that is divided in two different embryos, and fraternal twins come from two different zygotes fertilized by two different sperm cells.

Twin differences. Picture from www.genomesunzipper.org

Ok, until now it seems easy, more or less. But in real life, what can make us differentiate between both types of twins? Here some clues:

The Puffin's Lair - Dont' panic!

Have you ever heard about fainting goats? There are hundreds of videos and jokes about them, but, despite how hillarious these goats can be, a genetic disorder is behind. 

Sicke cell anemia and Malaria

Sickle cell disease (SCD) is a genetic disorder that is characterised by a chronic anaemia occurring almost exclusively in individuals of African descent. Individuals afflicted with SCD are homozygous for a key mutation in haemoglobin, whereas individuals who are heterozygous for this mutation are generally asymptomatic and are said to have sickle cell trait. But, fortunately, individuals carrying just one copy of the sickle mutation were known not to develop sickle cell anemia, leading rather normal lives. It was discovered by Linus Pauling (two-times Nobel laureate).

Example of sicke cell trait. Picture from www.transfusionguidelines.org.uk

The Puffin's Lair - To be pink or not to be

Flamingos are wading birds and belong to the genus Phoenicopterus, which only consists in 6 species all over the world: 4 in the Americas and 2 in the Old World - Europe, Asia and Africa.

They are graceful birds, until 1.40 m height with long legs and long necks. Feet have 4 toes and when flying, both neck and legs are completely straight.

The end of the Romanovs

After the success of the Bolshevik Revolution, the Tsar Nicholas II of Russia abdicated in 1917. He and his family were taken to Yekaterinburg, where they were kept as prisoners and finally executed under direct orders of Lenin in 1918. Their bodies were buried in a mass grave and forgotten for decades.

Romanov's family. Picture from www.historyandwomen.com

Milk and Humans

Hello fellow! Back again with a genetic curiosity. Today, milk will be the main character.

From the beginning, humans and milk have been very related. In addition to the appropriate amounts of carbohydrate, protein and fat, breast milk also provides vitamins, minerals, digestive enzymes and hormones. All what is needed by babies.

Picture from www.myspaceantics.com

The Puffin's Lair - Hot N Cold

There are more than one way to determine the gender in nature. We humans depend on who is the carrier of the Y chromosome - XX female, XY male -. Other species such butterflies or chickens depend on the W chromosome - ZZ male, ZW female. But there is still another surprising possibility: the environmental sex determination.

Temperature plays a key role in a special type of this system, being very common in crocodilians, turtles and other reptiles. This nongenetic way of determine whether an egg develops as male or female occurs after fertilization.

For instance, in some turtle species, like Trachemys, eggs from colder nests result in all males, whereas eggs from warmer nests turn into females. In crocodilian species — the most studied is the American alligator— both low and high temperatures result in females, and intermediate temperatures become males.

Temperature-dependent sex determination in three reptile species: the American alligator (Alligator mississippiensis), the red-eared slider turtle (Trachemys scripta elegans), and the alligator snapping turtle (Macroclemys temminckii). (After Crain and Guillette 1998)

Inbreeding

Today's topic: Inbreeding. What is inbreeding and which problems brings with it?

For sure we all have heard about inbreeding. When we hear about the Amish, about some royal families or even in some historical games (Crusader Kings I and II), inbreeding is almost always present. It means marriage, union or reproduction between individuals of common ancestry, ie. of the same family or lineage.

Picture from xenohistorian.faithweb.com

Also, inbreeding usually represents something bad. Some traits come with it, such as reduced fertility, facial asymmetry, lower birth rate or increased genetic disorders (albinism, hexadactilia, etc.). But, genetically, why is inbreeding so deleterious?

The Puffin's Lair - Tamed foxes in Russia

There are two kinds of people in the world: those who love dogs and those who prefer cats. Until now.

Russian scientist Dmitri Konstantinovich Belyaev strongly believed that foxes can become the new human's best friend. He and his team spent more than 50 years trying to domesticate silver foxes, a melanistic form of the red fox -Vulpes vulpes.
The experiments began in the Soviet Union in 1959 and continue until today, carried out in the institute of Cytology and Genetics at Novosibirsk, Russia.

Bloody confusion!

We are back again! Sorry for the delay. Let me compensate you with a very useful explanation about blood groups and compatibility. The eternal confusion. Am I universal receptor? Who can donate blood to who?

There exist two different human blood group systems -actually there are 32, but those two are the most important ones-, ABO and Rh antigen. 

First of all, all of you should know that the dominance in ABO group is A and B co-dominant and O recessive. It means that if we have AA or AO genotype, the phenotype will be A, if we have BB or BO the phenotype will be B, with OO we have O, and with AB the phenotype is AB.

In case of Rh we have positive (+) or negative (-) genotype, the positive is dominant and the negative recessive.

Knowing that, now... who can donate to who? Here there is a very clear table about that:

The Puffin's Lair - Secret skin

The polar bear – Ursus maritimus – lives in the Arctic Circle and is the largest living bear in the world. In some places is also called the Maritime Bear, as in the scientific name, due to the time it spends living in the water. An adult bear weights from 300 kg to 700 kg, is carnivorous - is fond of seals – and not territorial, unlike grizzly bears. 

Epigenetics

As explained in the post About cloning..., when we talked about "surrounding DNA stuff", we were talking about epigenetics.

Epigenetics is the study of changes in gene expression caused by mechanisms in the underlying DNA sequence, some of which are inheritable. In other words, we do not depend only on our genetic code plus the environment to be as we are, we have our "genetic environment" inside that makes us different.

Differentiation process. Picture from www.systembio.com

The Puffin's Lair - The Puffin's tongue

As an Animal Biologist, when the mind behind Genetics and Beyond proposed me to divulge some curious aspects and facts of the wildlife, I rapidly agreed. Although all the animals are wonders of nature, I have chosen the puffin to inaugurate this blog section.

The Atlantic puffin (Fratercula arctica) is a black and white seabird with reddish legs that presents a shiny colourful beak during mating season – the couple remains together for a lifetime.

It can be mainly found in northern coast of Europe, Iceland and Faroe Islands, and lives in colonies near the cliffs, ready to dive and get some squids and seafood.

However, what it likes the most is fish. And here it comes the amazing feature. If you have seen a bird diving for fish, they usually take out from the water one fish. The Atlantic puffin can catch and hold with ease about 10, each trip.

The puffin’s tongue is special, as is shown in the picture. It uses its raspy tongue to push the fish against spines on the palate while they continue fishing. Each time another fish is caught; the tongue pushes again and holds it up with the others.

About cloning...

I am sure that all of you have heard about cloning before. Despite of being a scientific invention or discovery, it has existed from long time ago in nature. It is also called asexual reproduction. It happens, for example, in bacteria. But it also happens in higher animals. 

Example of fragmentation in a starfish. Picture from blocs.xtec.cat

Cloning is an identical copy of an individual, organism or cell that already exists. 

But coming back to more human concepts, cloning has been one of the most interesting issues in science since the discovery of the DNA. The idea of creating a new individual with exactly the same genome as another... it almost means immortality. But we can discuss about philosophical meanings later.

Picture from www.neatoshop.com