is one chromatid = DNA (two stranded) because i have read online that it is one strand of the double helix DNA, but then according to my genetic class and what i remember of the holliday model, one chromatid is a molecule of DNA.... Can someone clarify this for me?


Thanks

Chromosome – one single strand of DNA. During most of the cell’s life (G1), the cell has 46 chromosomes, each a single segment.

Chromatid – During (S) of interphase, the single strand is copied. The two copies then form the X configuration in prophase. Here there are still 46 chromosomes (even though the genetic material has doubled), each consisting of two identical sister chromatid. So a single chromatid is one half of the X.

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ok m confused! i thought DNA are on the genes....1 dna = 1 chromatid? never knew that

I would say yes and no.

Genes are in DNA, not the other way around:

“A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell. It is a very long, continuous piece of DNA (a single DNA molecule), which contains many genes, regulatory elements and other intervening nucleotide sequences. A broader definition of "chromosome" also includes the DNA-bound proteins which serve to package and manage the DNA.”

So:
1 large macromolecule of DNA (with histones and all the goodies) = 1 chromosome

When this single chromosome is copied and connected to the original as an X this = 1 chromosome still, but now composed of two identical sister chromatid.

right chromosome has all the DNA & genes & stuff...but that doesnt apply that 1 chromatid = 1 DNA..there are trillions of DNA in our body. we only have 92 chromatids that doesnt mean we have 96 DNA. I thought that is what the op was asking...that's y i got confused!