Wednesday, May 29, 2013

DS 101 - The Basics

Six months ago all I knew about Down syndrome came from some mostly-forgotten high school biology classes and Glee.  I’ve spent an awful lot of time in the past few months reading while nursing, and slowly learning the shorthand & assumptions of this club we’ve joined.  I'm still learning, but I'm finding that summarizing and writing it down helps me process and understand.  And I’ve gotten quite a few questions from friends (and probably a few more questions have gone unasked), so I thought I’d put together a few posts about the basics of Down syndrome.

Down syndrome, it turns out, works an awful lot like a Game Genie.  Back in the day, did you have a Game Genie for your Nintendo?  It was a device that fit between the game cartridge and the console.  Before the game started up, it gave you a chance to type in about six codes.  Each code was a series of numbers and letters that would go in and alter a line of the game’s computer code.  The code might give you unlimited lives or make the baddies move more slowly.  Codes could be found in books and on the back of game boxes and, of course, in Nintendo Power magazine.  Or—and this is how my friends and I mostly used the device—you could make up your own codes and play through the game trying to figure out what changed.

Sometimes the change made game play harder—the clock would move faster or the power-ups wouldn’t work.  Sometimes the changes were benign—once we managed to turn the game’s sky purple.  Sometimes we would play through the whole game and never figure out what change had occurred.

Down syndrome works just like that.  See, when a man and a woman love each other very much, they each contribute 23 chromosomes to their offspring.  Each of the 23 pair up, so that the baby’s first cell, and every cell that grows after that, has a total of 46 chromosomes.  But sometimes the mom’s or dad’s (okay, usually the mom’s) original chromosomes don’t separate the way they should.  All of the pairs split up except for one, and that one hangs along for the ride.  When the egg is fertilized that first cell, and every cell that divides from it, has 47 chromosomes.

The chromosome pairs are numbered in order from longest to shortest.  For some reason, I find it fascinating that chromosomes come in different lengths.  I must have missed that day in high school biology.  Anyways, they are numbered in order, but 23 gets the last number because it’s the pair that determines sex—the one that is either an X or a Y.  And then whoever named the pairs measured 21 and 22 wrong.  So that is how the shortest pair ended up with the name 21.  When a person has 3 copies of chromosome 21, they have Down syndrome—also clinically called Trisomy 21.

You can have extras of other chromosomes, or extra parts of other chromosomes.  Some of these cause other rare genetic syndromes.  But usually, if a complete longer chromosome comes along for the ride, the fetus doesn’t even make it to term.  It’s really something of a miracle, and a testament to the human body’s amazing adaptability, that a baby with an extra set of code can survive at all.

Just like that Nintendo Game Genie, the extra code scrambles things a bit.  And since everyone’s genes are a bit different, we don’t know exactly where the extra chromosome’s influence will show up.  Sometimes the effects are benign.  People with Down syndrome often have only one crease across their palm (Max doesn’t, he has three), and they often have a larger space between their first two toes (Max does have this marker.)  Some changes alter the game play a bit.  People with the extra chromosome tend to have shorter limbs in relation to their torso, for example, and that will affect the way Max learns to crawl and walk, although it shouldn’t affect how he walks once he learns.  And some changes make the game more difficult.

Just like with any other baby, we won’t really know where Max’s strengths and challenges lie until he gets older.  The down side to having a label so soon is that we got hit with a lot of worry right when he was first born, and Max will always have folks see his diagnosis first before they get to know him.  Having a diagnosis so early can be useful, though.  It means we qualify for early intervention services from day one.  It means we know what medical conditions to screen for at certain ages.  And since Down syndrome is the most common chromosomal condition, there is a lot of research on what sort of therapies and teaching may work well for him.  For example, people with Down syndrome tend to be visual learners—so our therapists will likely work with us to teach him skills using pictures and sight words alongside verbal instructions.

And, of course, there are still 46 other chromosomes at play. So, Max has still inherited a possibility of my high cholesterol or Christer’s allergies.  He might end up with my artistic interests or Christer’s talent for numbers.  He’s just got a few extra lines of code mixed in with what we were expecting.

1 comment:

  1. Great and informative post! Thank you for taking the time to write it all out. Also in good timing, one of my favorite bloggers posted a great post about DS: