Chromosome 2 - What happened?


(Mike Sovocool) #1

So reading and watching youtube videos (Please don’t judge), I learned about Chromosome 2. A Chromosome that supposedly was fused from 2 ape Chromosomes.
After watching both sides of the debate, My wife made an interesting inquiry.

If apes have 48 Chromosomes and Humans Have 46 Chromosomes, and one fused, wouldn’t that leave 47?

I have searched all over for an answer and can not locate anything about a missing Chromosome.

I did read an article last year that someone basically said, “We didn’t need it so our body got rid of it”.

This brought up a flurry of issues to me. For now, I’ll egress, Do we have a missing Chromosome that we can relate back to apes, and if so, what happened to it? If we lost that chromosome, wouldn’t that mean a major loss of information?

Any info or articles would be super appreciated.Thank you.


#2

It is interesting to note that they have found a man with 44 chromosomes in China, and he is perfectly healthy and normal. He has a fusion of chromosomes 14 and 15. This arrangement can be passed on, and if his descendants meet and have offspring in the future then they will have children with 44 chromosomes.

http://genetics.thetech.org/original_news/news124


(Mike Sovocool) #3

But why doesn’t he have any problems? A loss of one let alone two chromosomes is almost always fatal because so many essential genes are lost.

In this case, he has fewer chromosomes but is actually missing very few genes. Instead, he has two chromosomes stuck to two other chromosomes. More specifically, both his chromosome 14’s are stuck to his chromosome 15’s.

Wow! Thanks again! That answered a lot of questions!
Now off to find that missing Chromosome!


(George Brooks) #4

@Mike_Sovocool, Please be careful about the phrasing: “ape chromosomes”. Those chromosomes fused some time after our ape lineage separated from the common ancestor we share with chimpanzees.

I see that @T_aquaticus has saved the day with a relevant link to an article.

If you remember that our 46 Chromosomes are really 2 sets of 23 unique chromosomes, it is easier to realize that the fused chromosomes replicated the fusion as well … which explains how the loss of a chromosome count got multiplied by 2!.


(Mike Sovocool) #5

what would the correct term be?


(Curtis Henderson) #6

We have 23 pairs of homologous chromosomes (if you count the sex chromosomes) and the evidence strongly supports the merging of two pairs. So if we account for the same event in both our maternal and paternal chromosome sets, the reduction from 48 to 46 makes sense.

The hypothesis suggests that the reduction happened by Robertsonian translocation. Basically, this type of event fuses the two “long” arms of two separate chromosomes together into one and the two “short” arms together. Often this fused short-arm product does contains little coding information, so the loss of that product is negligible.

You can read a little more about Robertsonian translocation at this wiki site – https://en.wikipedia.org/wiki/Robertsonian_translocation.

Thanks, Mike, good questions!

(Oops, sorry for the redundancy!)


(George Brooks) #7

I think the term “ape” as you have used it is not wrong. I was actually thinking about how someone else would abuse the term. I kept waiting for someone to say those two fused chromosomes are Chimpanzee chromosomes… and that would have made me wince.


(Matthew Pevarnik) #8

Edit: more redundancy with some new info while I was resetting my router :slight_smile:

When we label chromosomes it is 1 through 23. Since you inherit one from you dad and one from your mom you end up with 46.

Other primates have theirs labeled 1 through 24. Since primates have one dad and one mom they get 48.

Here’s a nice article summarizing what chromosomes are, noting that:

you increase the chances of losing some important file folders in the process, and making it more difficult to sort out important information — but it’s not as drastic as some seem to think, and chromosome numbers can change dramatically with no obvious effect on the phenotype of the organism

https://www.google.com/amp/scienceblogs.com/pharyngula/2008/04/21/basics-how-can-chromosome-numb/amp/


(Mike Sovocool) #9

Thank you everyone. I now have a few more spring boards to jump off in my quest for knowledge! Thanks Again!


#10

That would be opening a big huge can of worms labeled “Cladistics Nazi”. :wink:

The real problem is that “ape” is not a true scientific group, in the most strictest sense. In cladistics (the science of grouping species), you only use monophyletic groups which is a common ancestor and all of its descendants. Any group that includes chimps, gorillas, and orangutans must also include humans since we are descendants of the same common ancestor. The scientific name for this group is Hominidae. The term “ape” is paraphyletic group since it excludes some of the descendants.

English has a lot of paraphyletic terms, such as “dinosaur” which excludes birds. Scientists also use colloquial terms which are paraphyletic, and that only adds to the confusion. Should we also include humans in the term “ape”? Should we continue to use the colloquial term that excludes humans even though it isn’t scientific? Suffice it to say, there are many different views on the subject.


(Phil) #11

Great answers, but this brings up another question. AIG writes about how the chromosomes really are not fused etc. Here is a sample article of what they say, which sounds pretty flimsy but anyway: https://answersingenesis.org/genetics/dna-similarities/chromosome-tales-and-importance-biblical-worldview/
Any thoughts on their explanation from those who know?


(Curtis Henderson) #12

Dennis Venema wrote about this several years ago, and I doubt I could add much that he doesn’t cover!


(Steve Schaffner) #13

Just to confuse matters, chimpanzee and gorilla chromosomes are numbered 1 through 23 (or 1 through 22 + X/Y) just like humans. Two of their chromosomes are numbered 2a and 2b, to make it easier to compare to human chromosomes. A trifle speciest, if you ask me.


(Mike Sovocool) #14

OK. I am way out of touch with terminology. It seems thats what was my downfall on searching for answers.

I got answers to my questions and answers to questions I haven’t thought of yet. I guess I will spend the day going through all the posts and learning.

Its nice to ACTUALLY FIND A GROUP THATS WANTS TO TEACH and not condemn.

Thanks again everyone.


(system) #15

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