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

2. The Cell CycleThe 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 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?