Genetics behind dwarfism



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Dwarf vs size 12 shoe


What is it?
"Dwarfism is short stature resulting from a particular medical condition. It is sometimes defined as an adult height of less than 4 feet 10 inches" (Dictionary.com)

Signs and symptoms:

  • Slow growth before age 5
  • Periods of little or no change in height
  • Height below the fifth percentile on standard pediatric growth charts
  • Delayed or no sexual development during adolescence
  • Adult height usually less than 5 feet

The symptoms of Disproportionate Dwarfism are:
  • An adult with an average height of about 4 feet
  • Short arms and legs, especially upper arms and legs
  • An average size trunk
  • Short fingers, usually with a wide separation between middle and ring fingers
  • Progressive development of bowed legs
  • Limited mobility at the elbows
  • Progressive development of swayed lower back
  • A disproportionately large head, with a prominent forehead and flattened nose bridge

Possible complications

Disproportionate dwarfism can cause such problems as:
  • Delays in motor skills development, such as sitting up, crawling and walking
  • Frequent ear infections and risk of hearing loss
  • Bowing of the legs
  • Difficulty breathing during sleep
  • Pressure on the spinal cord at the base of the skull
  • Excess fluid around the brain
  • Crowded teeth
  • Progressive severe hunching or swaying of the back
  • In adulthood, narrowing of the channel in the lower spine, resulting in pressure on the spinal cord and subsequent pain or numbness in the legs
  • Arthritis in adulthood
  • Weight gain that can further complicate problems with joints and the spine and place pressure on nerves


What causes

The main causes of dwarfism can be:
  • Achondroplasia
  • Turner Syndrome
  • Growth Hormone Deficiency
  • Primordial Dwarfism

Prevention

Unfortunately, most types of dwarfism are unpreventable, because they are caused by gens. Genetic conditions that cause dwarfism may be identified with genetic testing, by screening for the specific variation that result in the condition. However, due to the number of causes of dwarfism, it may be impossible to determine definitively if a child will be born with dwarfism.


Treatment

Most people with dwarfism have orthopaedic or medical complications. Treatment of those include the followings:
  • Insertion of a shunt to drain excess fluid and relieve pressure on the brain.
  • A tracheotomy to improve breathing through small airways.
  • Corrective surgeries for deformities such as cleft palate, club foot or bowed legs.
  • Surgery to remove tonsils or adenoids to improve breathing problems related to large tonsils, small facial structures, and/or a small chest.
  • Surgery to widen the spinal canal (the opening through which the spinal cord passes) to relieve spinal cord compression.





Can two dwarfs have an average height child?

Everyone has two copies of most genes, one from mom and one from dad. And our genes can come in different versions called alleles. The
gene called FGFR3. Most of the time this gene results into average height, but some times it can result into dwarfism. When dwarfism occurs it means the person has one copy of FGFR3 that causes dwarfism and one that does not. Even though the gene for dwarfism is dominant over the gene for average height, if two dwarf parents had a child there's still a fifty fifty chance of them passing down a gene that doesn't cause dwarfism.

25% of the time, the child will get a copy of the average height gene from both parents. The result will be a child of average height.


D- Dwarfism
d- average height
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This is a punnet square that shows a child with two dwarf parents can be average height (dd).



Do dwarfs have to have dwarf parents?

No, dwarfs can have average sized parents because 7 out of 8 cases of dwarfism result from DNA changes in the FGFR3 gene that happens at random. These changes (or mutations) happen in the sperm or the egg or very early on in development, and of course this brings up the most important point that genes are not written in stone. They are written in DNA, and DNA can change.
DNA is made up of four letters that spell out, in three letter words, the instructions found in a gene for making a protein. A mutation happens when something in that series of letters changes.Either one or more letters go missing, an extra letter or more is added, or the letters are changed to a different letter, and also these changes alter the instructions giving a different version of the protein.


Further readings and references:


http://genetics.thetech.org/ask/ask179
http://en.wikipedia.org/wiki/Dwarfism
http://www.mayoclinic.com/health/dwarfism/DS01012/DSECTION=symptoms
http://www.youtube.com/watch?v=nzsdfSDMj64










Extinction


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Wooly Mammoth- most became extinct about 11 000 years ago


What is extinction?
is when a animal or plant doesn't exist any more, because all of its species has died out completely.
More than 90 percent of all organisms that have ever lived on Earth are extinct.

It's estimated that 137 species disappear each day, meaning 50,000 species disappear every year. This means within 25 years 10% of our population will die out. Experts say that at least half of the world’s species will be completely gone by the end of the century.
Extinction is a natural result of evolution and natural selection. Species go extinct when they are unable to adapt to changes in their environment or can't compete with other organisms.

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This graph shows that in the past 1000 years extinction rates went up majorly


Different types?

  • Natural extinction- When a species declines in numbers gradually but steadily. The length of the period depends on the success of the species and its ability to adjust to changes in climate, vegetation and the appearance of predators.
  • Direct extinction- When Humans destroy animals that they become completely exterminated and no longer exist as a species.
  • Indirect extinction- When humans indirectly affect animals habitats.



What are human causes of extinction?
  • Increased human population
  • Destruction of Habitat
  • Pollution
  • Climate Change/Global Warming
  • Hunting
  • Taking animals for profit




What are natural causes of extinction?

  • Climatic heating and cooling
  • Changes in sea
  • Acid rain
  • Disease
  • Asteroids


Some animals that have gone extinct


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Tyrannosaurus Rex, believed to have become extinct 6 million years ago.



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Half zebra half horse, became extinct in 1883




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Steller's sea cow, became extinct in 1768




Further readings/ References:






Puberty


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The changes the male's body undergoes.The changes the female's body undergoes.



What is it?
The time when your body begins to develop and change as you grow older. During puberty, your body grows faster than any other time in your life, except when you were a baby.



What happens to your body?
During puberty, your body will grow faster than at any other time in your life, except for when you were a baby. When your body is ready to hit puberty your pituitary glands releases hormones,
what these hormones do depend on your gender. But these hormones can also get blamed for lots of other things like acne, moodiness, tiredness, bad temper, greasy hair, sleeping a lot.


Male ( Hit puberty between 10-18)
In males the hormones travel through the blood down to the testes, which causes testosterone and sperm
to start being made. Testosterone is the hormone that makes
most the changes in the males body happen.
Boy's bodies become more muscular and their shoulders become wider.
Voices crack and become deeper. Their penis grows longer and wider and their testes get bigger.



Female ( Hit puberty between 8-17)
In females these hormones travels to her two ovaries, which carry
eggs inside. The hormone causes the ovaries to start making another hormone (estrogen).
These hormones together prepare a female's body to start her period ( a monthly cycle when blood is released through the vagina).
Girl's bodies become more curvier and their breast develop, and hips usually grow wider.



Both male and female
Both male and female begin to grow hair under their arms,on and around pubic area.
They have a growth spurt, some teens grow 4 more inches in a year.
Both genders may experience oily skin and pimples. Some teens also experience body
odor.


Can puberty be delayed?
Yes, by a few different reasons. Sometimes it can be from a medical reason. If the child exercise a lot and has little body fat, or sometimes it can just run in the family.


Further readings/ references: