Unit VI: Cell Growth and Division Making more cells, making sex cells, and the problems that can occur

Organisms grow because they __________________ A. Limits to Cell Growth Organisms grow because they __________________ The elephant is larger because it has more cells 1. The larger the cell the ________________________ DNA ____________ cell activities In large cells  unable to keep up with the need of information 2. The larger the cell the ________________________________________ The exchange of materials depends upon _________________ The rate at which nutrients are used up and wastes are made depends upon the cells volume (what is happening inside) _____________________________

B. Cell Division Reduces volume increase ratio of surface area: volume _____________________ Reduces volume increase ratio of surface area: volume 1. Chromosomes made of ________  carry genetic information human cells – 46 chromosomes in 23 pairs ___________________ _________________ usually chromosomes are in the form of chromatin during cell division chromatin condenses and becomes visible chromosomes 2 identical sister chromatids connected with a centromere

2. The Cell Cycle The cell grows, prepares for division, and divides into daughter cells

3. Mitosis 4. Meiosis There are two different types of cell divisions for two different purposes Mitosis and Meiosis are very similar processes but with some major differences Mitosis is used for ________________________________ the organism. In some organisms it is used for ___________ __________________ Meiosis is only used to ______________________ (sex cells) used in the process of __________________

Mitosis Meiosis Prophase I Prophase - _____________ condenses into _____________ (become visible) - centrioles separate and move to opposite sides of the cell - centrioles form ____________ *in plants – no centrioles, spindle forms from ________ in the cytoplasm - nuclear membrane __________ _____ ____________ = pairing of homologous chromosomes chromosome + copy + homologous + copy total of 4 chromosomes = ____________

Mitosis Meiosis Metaphase I Metaphase - Tetrads line up in the middle - _______________ = homologous chromosomes switch pieces “new combinations of alleles”  ___________ - chromosomes line up in the _________________ - chromosomes attach to spindle at their ______________

Mitosis Meiosis Anaphase I Anaphase - ___________________ - Chromosomes separate - _________________ apart – migrate towards the centrioles - in late anaphase ______________ starts _____________ = tetrads separate and migrate to opposite sides of the cell

Mitosis Meiosis Telophase I Telophase - chromosomes gather at opposite ends of the cell (poles) - chromosomes unravel - nuclear membrane reforms - ___________ finishes Daughter cells are __________ ___________t 2 new _________ ___________ daughter cells are formed Mitosis is done Restarts the cell cycle Cells take a brief rest and then start the next division

Meiosis - The process starts again but with ____________ *remember mitosis is done This is the 2nd division of meiosis Meiosis Prophase II - The process starts again but with ____________ - ________________________ - Chromosomes condense and become visible, nuclear membrane disappears, centrioles migrate, and spindle starts to form

Meiosis - Chromosomes line up in the middle *remember mitosis is done This is the 2nd division of meiosis Meiosis Metaphase II - Chromosomes line up in the middle - __________________________ - Centromeres replicate so chromatids can separate

Meiosis - Chromatids separate and migrate *remember mitosis is done This is the 2nd division of meiosis Meiosis Anaphase II - Chromatids separate and migrate Single pieces – not homologous pairs - Cytokinesis starts to separate the cytoplasm

Meiosis - Nuclear membrane reforms *remember mitosis is done This is the 2nd division of meiosis Meiosis Telophase II - Nuclear membrane reforms - ___________________________ 1 Cell  4 cells - Each has ___________________________ as the original parent cell - _______  _______ ________  __________ - The distribution of homologous chromosomes is _________  thus _______________ frequently occurs

Mitosis Meiosis 5. Comparing Mitosis and Meiosis Mitosis vs Meiosis Type of Cells # of Daughter Cells Chromosome # # of Divisions Homologous Pairing Crossing Over Compare DNA Type of Reproduction

C. Uncontrolled Cell Growth ________________ = cells lose ability to control mitosis Form masses of cells = _________________ __________________ = cancer cells break loose and spread inside the body Genetic and Environmental Links

D. ______________ Humans are created from 1 single fertilized cell Every cell in the body has the ______ ____________________________ Cells ______________ and become all types of cells Specialized cells only use certain _____________________ Once cells are specialized they can’t go back Stem cells are cells that can become all different cells Stem cells come from embryos? ? ?

E. Gamete Formation _____________ = sex cell Sex cell = ____________ and ___________ (in plants pollen and ovum) Happens by ___________  reduces the number of chromosomes so offspring don’t have extra chromosomes

Mitosis Meiosis Questions How does the number of daughter cells produced from mitosis and meiosis differ? How does the ploidy of the daughter cells produced from mitosis and meiosis differ? Do the daughter cells produced from mitosis contain identical genetic complements? Do any of the daughter cells produced from meiosis contain identical genetic complements? When do the homologous chromosomes separate during mitosis? When do the homologous chromosomes separate during meiosis? When do sister chromatids separate during mitosis? When do sister chromatids separate during meiosis?