and...(e) sister chromatids.
biology's killing me.
biology's killing me.
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Chromatin is a long, thin molecule consisting of DNA and associated proteins, such as histones. A single chromatin "thread" is one complete DNA double helix with histones and other proteins attached.
The histones form octamers that form little semi-spherical clusters. The DNA strands then spool around the histones, as if someone were wrapping a mouse cord around a mouse a couple time. A single histone octamer cluster with its DNA wrapped around it is called a nucleosome. A chromatin "thread" has thousands or millions or more nucleosomes along its length.
Here is a picture of chromatin with nucleosomes (what they label as nucleosome core particles are the histone octamer clusters).
http://edoc.hu-berlin.de/dissertationen/…
During cell division, chromatin strands condense -- they get thicker and shorter as coiling and then folding upon coils and further coiling occurs.
Here is an image that tries to show how chromatin gets packaged to become shorter and thicker.
http://academic.pgcc.edu/~kroberts/Lectu…
When the chromatin "threads" become short and thick enough to be visible structures - which occurs in prophase - they are called chromosomes. And the end of mitosis and meiosis - in telophase - the chromsomes begin decondensing back into long, thin chromatin "threads".
Before cell division, each chromatin "thread" is a single structure. But in the S phase of interphase, each chromatin "thread" is replicated, with the two identical copies remaining attached at a pretty much central location on them. When the chromatin then condenses into chromosomes, the two attached structures are called sister chromatids.
Here is an image of a single chromosome composed of 2 sister chromatids.
http://www.macroevolution.net/images/sis…
So in prophase and metaphase, a chromosome consists of 2 sister chromatids attached at their centromere. In anaphase of mitosis, the centromere is broken and the two sister chromatids are separated. At that instant, each one is then called a chromosome. So what were 2 sister chromatids of a one chromosome, become 2 chromosomes once they are separated.
The histones form octamers that form little semi-spherical clusters. The DNA strands then spool around the histones, as if someone were wrapping a mouse cord around a mouse a couple time. A single histone octamer cluster with its DNA wrapped around it is called a nucleosome. A chromatin "thread" has thousands or millions or more nucleosomes along its length.
Here is a picture of chromatin with nucleosomes (what they label as nucleosome core particles are the histone octamer clusters).
http://edoc.hu-berlin.de/dissertationen/…
During cell division, chromatin strands condense -- they get thicker and shorter as coiling and then folding upon coils and further coiling occurs.
Here is an image that tries to show how chromatin gets packaged to become shorter and thicker.
http://academic.pgcc.edu/~kroberts/Lectu…
When the chromatin "threads" become short and thick enough to be visible structures - which occurs in prophase - they are called chromosomes. And the end of mitosis and meiosis - in telophase - the chromsomes begin decondensing back into long, thin chromatin "threads".
Before cell division, each chromatin "thread" is a single structure. But in the S phase of interphase, each chromatin "thread" is replicated, with the two identical copies remaining attached at a pretty much central location on them. When the chromatin then condenses into chromosomes, the two attached structures are called sister chromatids.
Here is an image of a single chromosome composed of 2 sister chromatids.
http://www.macroevolution.net/images/sis…
So in prophase and metaphase, a chromosome consists of 2 sister chromatids attached at their centromere. In anaphase of mitosis, the centromere is broken and the two sister chromatids are separated. At that instant, each one is then called a chromosome. So what were 2 sister chromatids of a one chromosome, become 2 chromosomes once they are separated.
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They all relate to being parts of a cell.
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They are found in the NUCLEUS of a cell