Mitosis160-page3 - the two sister chromatids comprise one...

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Cell Reproduction: Mitosis - 3 Chromosome Terms before and after Duplication An unduplicated chromosome is one chromosome. A chromosome more or less consists of two arms that extend from a centralized region called the centromere. When a chromosome duplicates, it becomes one duplicated chromosome, and the two copies remain attached to each other. It is still one chromosome. The two exact copies of the duplicated chromosome, which remain attached at the centromere region, are called "sister" chromatids. They are identical to each other. (Remember this; it is essential!) At the centromere region of the duplicated chromosome, there are structures (made of protein and DNA) called kinetochores. The kinetochores attach to microtubules of the spindle during mitosis. After the identical sister chromatids are separated during mitosis, each (called a "daughter" chromosome now) becomes a single unduplicated chromosome again. Rule to remember: A chromatid must be attached to its identical chromatid and
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Unformatted text preview: the two sister chromatids comprise one duplicated chromosome (not a pair of chromosomes "chromosome pair" is used for something else). "Sister" chromatids are not two chromosomes. They are one duplicated chromosome that consists of two identical chromatids. The only time you can use the word chromatid is when you have the two identical chromatids attached to each other. Homologous Chromosomes When we look at the chromosomes of most eukaryotic organisms carefully, it can be seen that for each individual chromosome, a second chromosome can be found that physically matches it in length and shape. Closer inspection of the DNA shows that the matching chromosomes have very similar, but not identical DNA which carries equivalent genetic information, or genes. These matching chromosomes, called homologous chromosomes, with their similar DNA, form the basis of the variation we see in the genetic traits, or genes, of living organisms ( see later )....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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