Genetics notation

[Mike59]

Hi all,

Can someone please help me "decode" this translocation:

t(9;22)(a34;q11)

Is there a resource online that teaches one how to understand these fancy genetics notations? (or can someone please explain each component to me in a nutshell)

Thanks!

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[skiz knot]

Hi all,

Can someone please help me "decode" this translocation:

t(9;22)(a34;q11)

Is there a resource online that teaches one how to understand these fancy genetics notations? (or can someone please explain each component to me in a nutshell)

Thanks!

I think I can be of a little help.

t stands for translocation (duh, I'm sure you knew that)

(9;22) means it involves chromosomes 9 and 22 (sex or lowest # chromosome is listed first)

I am lost on the "a" so from here it gets to be a little more of a guess for me.

I believe the a34 refers to an event happening on chromosome 9
and I believe q11 refers to an event happening on chromosome 22.
With that said, I'll continue on with my quasi analysis.

Chromosomal areas are notated by number, then by p or q arm on either side of the centromere. Each p or q arm is broken down into regions 1-at most 3 based on visible land marks with numbering begining nearest the centromere. Then each region is broken down by bands and numbered begining nearest the centromere.
What is happening on 22 is there is a break within the first band (second #1) of the first region (1st #1) of the q (long) arm of the chromosome.

on chromosome 9 there is a break within the third region's 4th band (the distal tip)

I am thrown for a loop what the "a" signifies though. I looked online and saw the same myeloid leukemia with the "a" replaced with the more familiar "q", which would be understandable to me. I have also seen it on several sites with the "a" there so it leads me to believe it is not a typo, rather it is some subclassification that I don't understand.

Hope I was of some help. PM me if you have further q's and check this site out.
http://harrisons.accessmedicine.com...ed/harrisons/co_chapters/ch111/ch111_p11.html

 

[skiz knot]

does anybody know what the "a" stands for?

 

[mpp]

Could it be a typo?...I think it should be a q, since that's the translocation for CML.

 

[skiz knot]

Could it be a typo?...I think it should be a q, since that's the translocation for CML.

I thought that too, but I have seen it on a few reputable sites listed with an "a". I have also seen it with "q".

Check out the weblink from my previous post in this thread, or search for the genetic notation or "philadelphia chromosome."

Still am perplexed about what the a means.

 

[bms]

Hello,
I have been working in a Cytogenetics Laboratory for 4 years and I have never seen the letter "a" used to describe the breakpoints in a balanced reciprocal translocation in cytogenetic nomenclature..... I asked one of the Co-directors of the laboratory & he stated it was a typo...

According to the ISCN (International System for Human Cytogenetic Nomenclature), the letters p & q are used to designate the short & long arms, respectively.

So, I wouldn't get to caught up with the letter "a". The important thing to realize is that "q" should be used instead of "a" to represent the break on the long arm of chromosome 9 (9q34) for this translocation. This is the "flagship" translocation that is used to teach students. I don't know why "a" is utilized on these websites when that provides little (if any) information about the location of the breakpoint.

 

[skiz knot]

Thanks BMS

 

[bms]

You're welcome skiz knot. By the way, your explanation of the nomenclature was great.

Also, to everyone & the OP, if you read the nomenclature out loud, it should be read as:
t(9;22)(q34;q11) --> translocation (9;22)(q "three four";q "one one")

and if there is a decimal point in the breakpoint such as 22q11.2, it should be read out loud as 22q "one one point two" & not 22q eleven point two, etc.

Have fun.