What are the components of a paired chromosome

1. Bellwork What are the components of a paired chromosome

2. Ch. 5 Cell Division Ch. 5.3- Maintaining The Chromosome Number

3. Target #20- I can explain how DNA condenses into a Chromosome • Eukaryotic chromosomes contain an enormous amount of DNA relative to their condensed length • All fits into the nucleus through a series of condensed packing • Primary system • The DNA strand wraps twice around proteins called histones • Creates a “beaded” chain • Each bead is known as a nucleosome, the basic unit of DNA packing • Occurs through positive histones creating bonds through attraction with negative DNA • Known as the DNA-Histone complex • Chromatin in it’s most fundamental form

4. Target #20- cont • Secondary System • The string of nucleosomes coils more densely • Called a 30nm fiber • Made of chromatin • Tertiary System • The 30nm fiber forms loops that are attached to non-histone proteins • Quaternary System • The loops fold in a zig-zag pattern • Most compacted form of chromatin • Shape most noted during Metaphase

6. Humans contain 46 chromosomes • Known as the diploid number contains two of each type of chromosome • 23 pairs • One member of each pair originates from each parent • All somatic cells are considered diploid cells • Contain a 2n nucleus • Creates 2n daughter cells • Sister chromatids are separated during mitosis Target #21- I can explain diploid number

7. Target #22- I can describe what occurs during each stage of mitosis • Prophase • Early Prophase • Centrioles begin moving away from each other toward opposite ends of the nucleus • Spindle fibers appear between the separating centrioles • Nuclear envelope begins to fragment, and nucleolus begins to disappear • Chromatin condenses and chromosomes are now visible • Each is duplicated and composed of sister chromatids • Held together at the centromere • Late Prophase • Spindle begins forming • Chromosomes become attached to the spindle fibers • Centromeres attach to fibers called kinetochore fibers

8. Target #22- cont Metaphase Spindle fibers are fully formed Consists of poles, asters (an array of microtubules), and fibers Metaphase plate A plane along the central portion of the nucleus Chromosomes attached to kinetochore spindle fibers line up at the metaphase plate Anaphase The centromeres uniting the sister chromatids divide The sister chromatids divide and separate Create individual daughter chromosomes The spindle fibers shorten, pulling the chromosomes towards the poles

9. Target #22- cont. • Telophase • The spindle disappears • The nuclear envelope reassembles around the daughter chromosomes • each daughter nucleus contains the proper number of replicated chromosomes • The chromosomes become less compact

12. Target #23- I can identify the phases of mitosis in a diagram or on a slide

13. Target #24- I can differentiate between cytokinesis in animal and plant cells • Cytokinesis Animal cells • A cleavage furrow forms • An indentation of the membrane between the two daughter nuclei • A contractile ring made of actin filaments forms around the daughter cells • Tightens to separate the two cells completely

14. Target #24- cont • Cytokinesis Plant cells • A small flattened disc, called a cell plate, appears between the two daughter nuclei • The golgi apparatus sends materials via vesicles to the cell plate • Vesicles carry microtubules • Results in the formation of new cell wall