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I am confused and I think my questions are to check my thinking. I did read your explanation maybe it's the terms you don't understand. Mine is not the terms, but maybe connecting it to a karyotype.

So, I see 2 kinds of karyotype pictures; this I know: \"X\" chromosomes are diploid and undergo mitosis, 23 pairs of \"X\" in autosome cell (non-sex cell); \"l\" chromosome is a chromosome found in sex (somatic) cells, like Egg/Sperm; there are only 23 chromosomes, haploid, not in pairs. Does this make sense, or am I missing something?

What I need explained is this:
If you look at a karyotype, KARYOTYPE #1: sometimes you see some with a pair of \"X\" and KARYOTYPE #2: sometimes you see a pair of \"l\". (Look on karyotype to see the pair of \"l\").

My question #1 is: When I see the pair of \"X\" with 23 human chromosomes karyotype, am I looking at non-sex cells?

Question #2: Which karyotype will you use to determine a disorder?

To answer my own question, I think - since all the DNA is the same in every cell, the unknown genes wouldn't matter which cell you would look at, but if you are looking for Turner's Syndrome, then you would have to use a Somatic cell. Or does it really not matter if you have somatic cell autosome; which karyotype picture would I look at, the \"X\" pairs or the \"l\" sex cells?

THANK YOU! Sorry for the lengthy questions, trying to be specific and understand this confusing thing!

Question Date: 2018-02-12

Answer 1:

For your Question #1:
To clarify, it is not just the "sex cells" that have the sex chromosomes. All human cells have all 23 pairs (46) chromosomes - 22 pairs of "autosomes" and 1 pair of sex chromosomes. In cells of females, there will be two X chromosomes and in cells of males, there will be 1 X and 1 Y. So, you could look at either a somatic cell and still see sex chromosomes.

For your Question #2:
Here again, you want to clarify that the somatic and germline (gamete) cells all have the same chromosomes. Once you have this straight, you can definitely answer your question - you are thinking about it the right way except for that one little roadblock. Some disorders are linked to duplications or loss of sex chromosomes, others to autosomes. Some are associated with translocations (Down's syndrome is a good example). All of which can be assessed by karyotyping.

What you CANNOT determine by karyotyping are diseases or disorders associated with small (often single nucleotide) mutations - for that you need to sequence the DNA.

A really important piece of info to keep in mind is that even though all cells carry the same genetic material (DNA), the cells can take on different fates (or roles) based on what genes are actually expressed. For example, a cell in your retina and cell in your heart may express some of the same genes - those that are involved in basic metabolism, for example. But, those two cells have very different roles to play and so there will be a large number of genes that are differentially expressed between the two.

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