CELL GROWTH & DIVISION

Why do cells divide? DNA OVERLOAD 1. _____________________ As cell grows bigger demand on DNA “genetic library” becomes too great Material exchange can’t keep up 2. _____________________ As cell grows bigger demand for transport across membrane is too great

Need for these depends on ___________ Ability to transport of oxygen, food, waste across cell membrane depends on _______________ Need for these depends on ___________ SURFACE AREA CELL VOLUME As cell grows these DON’T increase at the same rate

BIGGER CELLS NEED MORE FOOD and OXYGEN, but CAN’T TRANSPORT IT FAST ENOUGH or IN BIG ENOUGH QUANTITIES! http://www.animationlibrary.com

mainly by increasing cell number Multicellular organisms grow mainly by increasing cell number

DNA CAN BE: SPREAD OUT IN NON-DIVIDING CELLS SCRUNCHED UP IN DIVIDING CELLS CHROMATIN CHROMOSOMES

DNA in PROKARYOTES BACTERIAL DNA is CIRCULAR HAVE ONE CHROMOSOME NO NUCLEUS

DNA in PROKARYOTES Plasmids are small circular DNA molecules Help bacteria to survive stress Antibiotic resistance Recombinant DNA technology Insulin: http://www.abpischools.org.uk/page/modules/diabetes/diabetes6.cfm?coSiteNavigation_allTopic=1

DNA in EUKARYOTES DNA is ROD-SHAPED CHROMOSOMES MANY PAIRS FOUND IN NUCLEUS DNA in one human cell would be about 6 feet long if it were all stretched out Light regions tend to be euchromatic, early-replicating and GC rich (Karyotype)

DNA in EUKARYOTES Diploid When a (somatic) cell contains two sets of chromosomes Humans: 2n=46 Haploid When a (gamete) cell contains one set of chromosomes Humans: n=23 Zygote Fertilized egg cell The cells are usually collected by one of two methods: amniocentesis or chorionic villi sampling Chorionic villi sampling reliability of results is less than with amniocentesis.  Light regions tend to be euchromatic, early-replicating and GC rich (Karyotype)

Chromosome structure Modifications such as acetylation or methylation of the histones can alter how tightly DNA is wrapped around them.

Telomere A region of repetitive nucleotide sequences Protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes Telomerase replaces telomeres Shortens each time a cell divides Associated with aging and cancer Telomerase replaces short bits of DNA known as telomeres, which are otherwise shortened when a cell divides via mitosis. https://www.youtube.com/watch?v=8_bNfQd7Smc

Chromosome structure CHROMATIDS CENTROMERE HOMOLOGOUS ______________ 2 identical arms _____________ constricted area holds chromatids together CHROMATIDS CENTROMERE HOMOLOGOUS __________________ PAIR 2 of each chromosome (one from mom; one from dad)

HOMOLOGOUS CHROMOSOMES SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT ______________! (Don’t have to have the SAME CHOICES) NOT IDENTICAL http://arnica.csustan.edu/biol3020/cell_division/cell_division.htm

CELL DIVISION in PROKARYOTES Bacteria reproduce using __________________________________ BINARY FISSION Form of asexual reproduction that produces identical offspring http://fig.cox.miami.edu/~cmallery/150/mitosis/fission.jpg

CELL CYCLE INTERPHASE – non-dividing phase G1- Grow bigger Cell is “doing its job” DNA is spread out as chromatin S - Synthesis (copy DNA) & chromosomal proteins G2- Grow bigger, make organelles & molecules needed for cell division Cell cycle is a series of events that cells go through as they grow and develop

CELL DIVISION MITOSIS – Nuclear division Prophase Metaphase Anaphase Telophase Cytokinesis – Cytoplasm divides G0 – cell stops dividing (Ex: nerve cell)

INTERPHASE (G1 - S - G2) Can’t see chromosomes In between divisions Cells are in this phase most of the time Can see nucleus DNA spread out as chromatin Can’t see chromosomes DNA gets copied (S) Cell gets ready to divide

PROPHASE 1st dividing phase DNA scrunches into chromosomes Centrioles appear in centrosome region & move to poles Nuclear membrane & nucleolus disappear Spindle fibers form & attach to chromosomes

________ region organizes spindle CENTROSOME Spindle MICROTUBULES are part of cytoskeleton

METAPHASE Chromosomes line up in ___________ middle

ANAPHASE Centromeres split Centrioles pull chromatids_______ apart

two TELOPHASE (reverse prophase steps) See ______ nuclei Nuclear membrane & nucleolus return Chromosomes spread out as chromatin Centrioles disappear Spindle fibers disappear

CYTOKINESIS Cytoplasm splits into 2 cells CLEAVAGE FURROW ANIMAL CELLS pinch cytoplasm in two with a ______________________ CLEAVAGE FURROW

CYTOKINESIS Cytoplasm splits into 2 cells PLANT CELLS can’t pinch because they have a sturdy ____________ Plant cells separate cytoplasm by growing a _______________ down the middle. CELL WALL CELL PLATE

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Chromatin Centromere Nuclear envelope Centriole Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Telophase Individual chromosomes Anaphase Nuclear envelope reforming

Cell Cycle includes M phase (Mitosis) Interphase is divided into G1 phase S phase Prophase G2 phase Metaphase Telophase Anaphase

Outline Mitosis http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect16.htm