Sunday, April 19, 2009

FYI #1 - How CF is Passed from Parent to Child

At the suggestion of a few people who said they'd like to hear more about CF, I've decided to do a series of "FYI Posts.". I'm glad to have this opportunity to spread CF awareness! I will try not to get too technical with these posts, but, as I am an engineer, that might be a challenge ;)

So, here is my first one.

Cystic Fibrosis is a recessive, genetic disease. The key word here is "recessive." Recessive means that a child must inherit two copies of the CF gene in order to have CF. A child who carries only one copy of the CF gene will not have CF. And, because a child receives one gene from each parent, if one parent is not a carrier of the CF gene, it is impossible for the child to have CF.

CF is just like just like blue eyes - remember that lesson in high school science? Well, if you don't, here's a recap: Every parent carries two copies of a gene for eye color. Blue is a recessive gene and brown is a dominant gene. If a child is born with one brown-eye gene and one blue-eye gene, the child will have brown eyes. A child must have two copies of a blue-eye gene in order to have blue eyes.

As I mentioned before, a child gets one gene from each parent. For two parents who are carriers of the CF gene, (e.g. my parents), here are the possible outcomes for a child.

So, as you can see, when two parents are carriers of the CF gene, there is a 1 in 4 (25%) chance their child will have CF.

Now, let's look at the case in which one parent has CF and the other parent is not a carrier. This almost certain is the case for Greg and I. The reason I say "almost certain" is because genetic testing, (which Greg has undergone), does not account for all of the CF genes (I will explain this more in the next FYI). There is still a 0.4% chance that Greg is a carrier. However, for the moment, we will look at that 99.6% chance. Here is a chart for a CFer having a child with a non-carrier.

As you can see, it is impossible for a CFer and a non-carrier to have a baby with CF.

Now to look at the 0.4% chance that Greg is a carrier. If that were the case, our chart would look like this:
If one parent has CF and the other is a carrier, they have a 50% chance of having a child with CF.

What all this means is Greg and I have a 0.4% x 50% = 0.2% chance of having a child with CF. In comparison, the average Caucasian couple has a 0.04% chance of having a child with CF, (so I was wrong in my comment response the other day).

So yes, Greg and I have a higher chance of having a child with CF compared to an average couple. However, 0.2% is a very small chance. To put it in even more perspective, 0.2% is the same chance a woman my age, (32.5), has of having a child with Downs Syndrome. It is a chance that we, and my doctors, feel very comfortable with.

21 comments:

Lindsay said...

Thanks for that! I feel much more informed now about a subject i knew nothing about. ;-)

Something Simple Design said...

Very good bio lesson, coming from the bio teacher ;) But, to be a nerd... there are actually 26 genes (52 alleles) for eye color. Just in case anyone gets stumped at how they got their eye color :)

Your the greatest for sharing your story :)

agarrisonrn said...

I think its crazy to even take that very small chance in inflicting a horrible genetic disease on your child. wow. talk about being selfish. Go to the state "foster to adopt" program instead .There are plenty needy children up for grabs. The state will even help fund the adoption. Maybe you could even adopt one with CF since you don't seem to mind.

Jennifer said...

So Agarrisonrn, what's your story. You seem so hell bent on bashing Kristen I figure you must have some beef with her or just life in general. Would you care to man up and provide us a link to your blog so we can see how perfect and wonderful your life is, or isn't?

JackiJaguar said...

agarrisonrn, you're a really shitty human. You should go run your keyboard over with your car...this whole typing thing really isn't working out for you.

ironbunny said...

agarrisonrn:
You are a douchebag.
How many children have you adopted? How many children have you fostered?

Kristen said...

AgarrisonRN, I deleted your last post because it so ridiculously ignorant (as is this one). However, this time, I am letting the world see A) What a douchebag you are, and B) What other CFers who are TTC might have to deal with.

Is it ok, in your opinion, for a woman in her 30s to have a child? Because they have THE SAME risk of having a baby with down's syndrome. Or what about cerebral palsy? Or Neural Tube defects? Those diseases have similar odds.

If you don’t want to be a hypocrite, maybe you should be run along and start spouting this shit on every single TTC blog because ALL couples are risking producing a child with some sort of genetic disease or birth defect.

And, what about a “normal couple” who STILL has a risk of having a baby with CF? Do you think they are being selfish too? Or did you sit there and think BEFORE I POSTED THESE ODDS “a 0.04% chance, that’s ok, but 0.2%, that where I draw the line.” I’m SURE that’s what you did.

Actually, what I am sure of is that you did not know what you were talking about, and you are too much of a douche to change your mind once the facts are laid out in front of you. If I had said we have a 0.002% chance, you would still be telling me how selfish I am.

I’m really am sorry you feel this way. Really, I am. I am sorry there is so much ignorance out there. Maybe it would benefit you and that RN after your name if you learned more about the subject.

pmarie33 said...

I wish you didn't have to respond to terrible people making stupid comments about something they know nothing about. It's such a waste of time and energy.

Now go make a beautiful baby =)

Christine said...

Agarrisonrn, the other posters have already commented on your ignorant posts, and I think Kristen has shown your complete lack of insight or thought.

People like you make me want to throw up.

Mari said...

What pmarie said!

Jennifer said...

So agarrison, do you like it when people judge you on being a single mother? Do you think they think of you as selfish? Yeah, don't think you would.

CottonSocks said...

agarrison - You are simply unbelievable.

I would imagine that 99.8% odds that Kristen won't have a child with CF would be sufficient for any sane person.

I would imagine that someone who actually lives with the disease might know a thing or two about how 'horrible' it is and whether or not it is worth the miniscule risk.

Further, it is not Kristen's responsibility to 'rescue' children from the custody of the state. Adoption is NOT a sure thing, especially foster to adopt programs. And it is disgusting to refer to those poor children as being up for grabs, as if they were some sort of disposable consolation prize.

What a disgusting person you must be, based on your ignorant attacks.

CottonSocks said...

Kristen - thank you for taking the time to educate folks on CF and how ttc with CF works. I find it fascinating - keep up the good work!

picunurse01 said...

I just have to say that this woman creates a BAD name for nursing. Agarrisonm, please do your research before harassing Kristen.

I've only known her online, but her postings are not ignorant nor cold-hearted. She has the best interest of her future child. She would not go into this blindly; she has done her research and medical checks. She has mentioned that if her husband was a carrier, it would really change her plans. However, given that he is not a carrier of the most common genes, it is a miniscule risk.

I am just so shocked how you come across as high and mighty as to what to do.

I am so glad I haven't yet posted my blog publicly because I am SURE you'd have comments for me. Yes, I am an adult with CF and want a biological child. Shame on me for risking 0.2%. I think I'd rather gamble on that than the other genetic diseases that can be just as (or MORE) devastating.

I'm also a critical care pediatric nurse practitioner and shake my head. Go back to to books and journals and THEN come post something relevant and educative BACKED by research, not by your own personal feelings.

Leave Kristen alone from your annoying posts.

JM

picunurse01 said...

Wow... I never thought I would continue to read utter stupidity and ignorance.

Agarrisonm, you are putting a bad rap on nurses. Please go research risks of other diseases that can be passed on from mom to baby. You will see that a 0.2% of passing on CF is not that horrible.

Funny thing... I calculated an "assumed" age of you from your resume. If you graduated with an AA degree in 1989, I put you at 20 years then. Therefore, you were born roughly in 1969, which puts you at 40 years old now. Your son was born in 2005, which makes him probably 4. So, you were 36 years old when he was born.
Do you know that the risk of Down's syndrome for a woman of 36 years of age is? ONE in 287, which is roughly 0.3%. Let's say, maybe you were 35 years old, so the risk is ONE in 365, which is roughly 0.2%.

HUH! A risk of 0.2-0.3% for downs... not different from Kristen's baby's risk for CF. I bet no one was yelling at you for being selfish for being pregnant at age 35/36...

Leave Kristen alone. She's a good person who has done a lot of research, considerable amount of thought about this decision. She's not blindly entering in a pregnancy like others in the world. Why don't you yell at the teenage moms' who get pregnant from lack of birth control, lack of abstinence, or inability to get out of a bad situation with their significant other.

I'm a nurse practitioner in pediatric critical care and I do my research before I comment on anyone's blog. Did I see Kristen scoffing at you or criticizing you for being a single mom? No. So back off and learn some proper manners. What compassion do you have as a nurse? I'd hate to have you as a bedside nurse after reading your comment. No empathy at ALL.

Put yourself in our shoes (as I have CF too and want a biological child). You will see that it's not black and white about having a child. When you are faced with infertility issues, it's painstaking and annoying to deal with people like you.

That's all for now unless you start provoking Kristen again.

Jenn

Shannon said...

Kristen- Im glad you took the time to post all that info on CF, thanks for sharing it.

To agarrison- Everyone has already said what I would have said but I just wanted to add a STFU. Seriously, your posts make me sad that someone (you) could be so ignorant and rude to another person.

Amy said...

I haven't commented on your blog in awhile, but I always read it. Thank you for taking the time to educate people about CF. It's clear that SOME people are complete morons and prefer to judge you. I think what you're doing is wonderful and I wish you all the best!

jessica said...

Agarrisonrn:
STFU and DIAF.

Nikki1007 said...

Agarrison- YOu are a judgmental whore. Did you have genetic testing done before getting pregnant? Well if you didn't shame on you for taking the risk to pass on some genetic disease you could be a carrier of. That was a very selfish decision.

Eilerts said...

agarrisonrn -- As an aside (in addition to you being an asshole), you are ignorant. There are sooo many factors that can affect a baby. A 0.4% chance is NOTHING. A woman has a better chance of drinking contaminated water and causing a birth defect than she does of passing on CF through genetics. Or exposure to a cold. Or air pollution. Unless you lock yourself in a bubble for the nine months you're pregnant, you can't guarantee a perfect baby. Amazing the human race has survived so long without your wisdom to guide them.

agarrisonrn said...

picunurse..
you calculated my resume? lol. not sure where you found your so called info, but I happen to be 31 not 40, and I have 7 children, 4 of whom are adopted. thank you very much. time for you to go do more "research" i think. where do you get this stuff? ha

 
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