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Chromosomes
Humans have 23 pairs of chromosomes
1 set inherited from mother
1 set inherited from father
https://bioinformatics.cs.vt.edu/~heath/IMAGES/human_chromosomes.gif
Chromosome
DNA is called chromatin when in cell during normal functioning of cell – cannot discern anything except nucleolus
DNA replicates When cell divides, DNA
condenses into tight “X” shape, one side the original and the other side copied DNA
http://www.yorku.ca/kdenning/images/bioanthropology/chromosome.jpg
Mitosis – Somatic Line
Mitosis
http://staff.kings.edu/kdils/StudentWork/Kalinay%20Lessons/lesson_plan_3_files/image007.jpg
Mitosis Stages - Interphase
Cell spends most of its life in interphase (G1)
Signaled to replicate DNA (S phase)
Cell resumes normal functions with replicated DNA (G2)
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Mitosis Stages - Prophase
DNA condenses Spindles form (they
organize and guide DNA as it separates to each side of the cell
Nucleus begins to dissolve
Spindle fibers attach DNA
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Mitosis Stages - Metaphase
DNA lines up along equator of cell
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Mitosis Stages - Anaphase
Spindle fibers attached to DNA shorten and DNA moves to one side of the cell Notice that arms
of the chromosome separate
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Mitosis Stages - Telophase
Cell begins to pinch in along the equator of the cell
Nucleus begins to form Mitosis
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Mitosis Stages – Interphase – 2 cells Cell spends most of
its life in interphase (G1)
Signaled to replicate DNA (S phase)
Cell resumes normal functions with replicated DNA (G2)
http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg
Meiosis – Germ Line
Sexual Reproduction In humans – 23 pairs of
chromosomes, or a total of 46 chromosomes 1 chromosome from
mother 1 chromosome from
father Meiosis Meiosis
http://www.accessexcellence.org/RC/VL/GG/meiosis.php
Meiosis Stages - Interphase
Cell spends most of its life in interphase (G1)
Signaled to replicate DNA (S phase)
Cell resumes normal functions with replicated DNA (G2)
http://www.dnaletters.com/img/3.gifhttp://www.realscienceprograms.com/files/IMAGES/egg_cell.jpg
Meiosis Stages – Prophase I
DNA condenses Replicated DNA from
adjoining chromosomes crossover
Spindles form (they organize and guide DNA as it separates to each side of the cell
Nucleus begins to dissolve Spindle fibers attach DNA
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Metaphase I
Replicated chromosomes of DNA lines up along equator of cell
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Anaphase I
Spindle fibers attached to chromosome DNA shorten and one of the pairs of chromosome of DNA moves to one side of the cell – or the other
Chromosome number in humans – 23 – no longer in pairs
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages – Telophase I
Cell begins to pinch in along the equator of the cell
Division not yet complete
NOTE – cells now only have half the chromosome number
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Prophase II
Spindle fibers form and attach to DNA
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Metaphase II DNA lines up along
equator of cell
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Anaphase II
Spindle fibers attached to DNA shorten and DNA moves to one side of the cell Notice that arms
of the chromosome separate
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages - Telophase II
Cells begins to pinch in along the equator of the cell
Nucleus begins to form
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Meiosis Stages – Interphase – 4 cells Cell spends most of
its life in interphase (G1)
Signaled to replicate DNA (S phase)
Cell resumes normal functions with replicated DNA (G2)
http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpghttp://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg
Fertilization (Humans)
Egg with 23 chromosomes
Sperm with 23 chromosomes
Fertilization – zygote with 23 PAIR of chromosomes!
TA DA! (Sea Urchins)
http://www.brown.edu/Courses/BI0032/gentherp/pronucl.jpg