IUBio GIL .. BIOSCI/Bionet News .. Biosequences .. Software .. FTP

Seeking clarification in understanding genetic concepts

Dean P McCullough dpmccul at comcast.net
Mon Apr 19 03:14:51 EST 2004

Lets see if this gets back to you.
To answer a few of your questions:

Given that the genome between mouse and human is at lest 99% the same, 
the differences between one human and another is at least 99.9% the 
same.  Thus, it is very important to get a baseline, from which we can 
study the very minor variations from one person to another.

It is well known that these minor changes can have a major impact on the 
individual.  For example, there is a phenomenon called tandem repeats 
where a small number (2,3,4) basis are repeated many times.  A number of 
genetic diseases have been traced to a different number of repeats in 
these tandem repeats.

As for meiosis, there is recent evidence that a woman continues to 
generate new eggs.  Meiosis occurs only in the sexual organs, and is not 
something (in humans) that occurs else where.  Also, keep in mind that 
the copied chromosome is not purely from the mother or father.  There is 
many crossovers from one side of the chromosome to the other.  Though 
there is a greater likelihood that adjacent genes on the same 
chromosomes are from the same parent, in general, across the chromosome, 
this is not true.  I do not believe we have a good handle yet on the 
expected number of cross overs that occur.

Hope this helps.

> Hello all,
> I'm trying to understand about genetic engineering by reading the
> relevant articles on www.wikipedia.org, but I'm having some difficulty.
> First of all, there's the article on genomes, where it says:
> "In biology, the genome of an organism is a complete DNA sequence of
> one set of chromosomes..."
> For me, this means that each genome will be different for each
> person. But I know that recently, there has been a project going on
> to describe the "human genome". I assume that this cannot then refer to
> a single person, but then how possible is it to arrive at a 'generic
> genome' for all of humanity?
> Also, I've been trying to understand meiosis. Am I correct in saying
> that this only happens when sperm or egg cells are being made?
> At what time in a human beings life would this be - is this a
> continuous process, or a one off? I ask, because I seem to recall
> reading that a woman has all the eggs that she will ever produce
> when she is born.
> Also, am I right in saying that each of these reproductive cells
> has a different combination of genetic material from the person
> that produces it, depending on which of the 23 chromosomes is
> selected from either his mother's chromosome set or his father's
> chromosome set and on the effects of 'crossing over' during meiosis?
> How much 'crossing over' actually takes place - does it occur at
> multiple points in each chromosome?
> Thanks in advance for any answers or confirmations.
> --
> Akin
> aknak at aksoto dot idps dot co dot uk

Dean P McCullough
410 997 7506

More information about the Biochrom mailing list

Send comments to us at archive@iubioarchive.bio.net