Cellular Division

Cellular Division

Mitosis

Meiosis

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


Mitosis Stages - Metaphase

DNA lines up along equator of cell


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


Mitosis Stages - Telophase

Cell begins to pinch in along the equator of the cell

Nucleus begins to form Mitosis


Mitosis Stages – Interphase – 2 cells Cell spends most of

its life in interphase (G1)




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)



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


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


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


Meiosis Stages - Prophase II

Spindle fibers form and attach to DNA


Meiosis Stages - Metaphase II DNA lines up along

equator of cell


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


Meiosis Stages - Telophase II

Cells begins to pinch in along the equator of the cell

Nucleus begins to form


Meiosis Stages – Interphase – 4 cells Cell spends most of

its life in interphase (G1)




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

Questions?

BJ Shaw Panochthus frenzelianus American Museum of Natural History 2004

Documents

Cellular Division