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CHROMOSOMES

CHROMOSOMES

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CHROMOSOMES

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  1. CHROMOSOMES

  2. What are chromosomes? • Chromosomes are compact spools of DNA. • Stretched out the DNA from one of your cells would be over 3 ft (1 m) long! • Think of chromosomes as "DNA packages" that enable all the DNA to fit in the nucleus of each cell. • We have 46 of these packages in each cell; we received 23 from our mother and 23 from our father.

  3. What do chromosomes look like? • Chromosomes are very small but when dyed can be seen with a microscope. • Chromosomes are best seen during mitosis (cell division), when they are completely condensed.

  4. How Do Scientists Read Chromosomes? • Scientists use three key features to match up the 23 pairs: • Size: This is the easiest way to tell two different chromosomes apart. • Banding pattern: The size and location of the bands on chromosomes make each chromosome pair unique. • Centromere position: Centromeres are regions in chromosomes that appear as a constriction.

  5. Chromosomes taken from dividing cells are attached to a slide and stained with a dye. This dye gives chromosomes a striped appearance because it stains the different regions of DNA.

  6. How are chromosomes organized? • A karyotype is built by arranging the chromosomes in declining order of size.

  7. The 23rd Pair: The sex chromosomes determine if the individual is a male or female.

  8. Normal Male Karyotype

  9. What’s different about this Karyotype?

  10. Why do scientists look at chromosomes? • Scientists can diagnose or predict genetic disorders by looking at chromosomes.

  11. What does this karyotype tell you?