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Unit VI: Cell Growth and Division
Making more cells, making sex cells, and the problems that can
occur
A. Limits to Cell GrowthOrganisms grow because they __________________
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) _____________________________
The elephant is larger because it has more cells
B. Cell Division _____________________
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
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 MeiosisProphase Prophase I
- _____________ 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 MeiosisMetaphase Metaphase I
- chromosomes attach to spindle at their ______________
- Tetrads line up in the middle
- _______________ = homologous chromosomes switch pieces “new combinations of alleles” ___________
- chromosomes line up in the _________________
Mitosis MeiosisAnaphase Anaphase I
- ___________________- Chromosomes separate- _________________ apart – migrate towards the centrioles- in late anaphase ______________ starts
_____________ = tetrads separate and migrate to opposite sides of the cell
Mitosis MeiosisTelophase Telophase I
- 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
MeiosisProphase II
*remember mitosis is done
This is the 2nd division of meiosis
- The process starts again but with ____________- ________________________- Chromosomes condense and become visible, nuclear membrane disappears, centrioles migrate, and spindle starts to form
MeiosisMetaphase II
*remember mitosis is done
This is the 2nd division of meiosis
- Chromosomes line up in the middle- __________________________- Centromeres replicate so chromatids can separate
MeiosisAnaphase II
*remember mitosis is done
This is the 2nd division of meiosis
- Chromatids separate and migrate Single pieces – not homologous pairs- Cytokinesis starts to separate the cytoplasm
MeiosisTelophase II
*remember mitosis is done
This is the 2nd division of meiosis
- Nuclear membrane reforms - ___________________________ 1 Cell 4 cells - Each has ___________________________ as the original parent cell- _______ _______ ________ __________- The distribution of homologous chromosomes is _________ thus _______________ frequently occurs
5. Comparing Mitosis and Meiosis
Mitosis Meiosis
Type of Cells
# of Daughter Cells
Chromosome #
# of Divisions
Homologous Pairing
Crossing Over
Compare DNA
Type of Reproduction
Mitosis vs Meiosis
C. Uncontrolled Cell Growth________________ = cells lose ability to control mitosisForm masses of cells = ___________________________________ = cancer cells break loose and spread inside the bodyGenetic 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
1. How does the number of daughter cells produced from mitosis and meiosis differ?
2. How does the ploidy of the daughter cells produced from mitosis and meiosis differ?
3. Do the daughter cells produced from mitosis contain identical genetic complements?
4. Do any of the daughter cells produced from meiosis contain identical genetic complements?
5. When do the homologous chromosomes separate during mitosis?
6. When do the homologous chromosomes separate during meiosis?
7. When do sister chromatids separate during mitosis? 8. When do sister chromatids separate during meiosis?