9-Cell Division and Mitosis lesson 9 -...

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CELL DIVISION AND REPRODUCTION: MITOSIS & MEIOSIS LESSON 9

What Do You Know?• On your notes, answer these questions: • When you scrape your elbow, how does it heal? • Why do you not just grow a new elbow? • How does your body know to grow skin cells as opposed

to bones cells? • Why is your new skin not a different color? • What does the cell theory state? • So, if cells come from other cells and cells are parts of

living things, how does that happen?

What You Will Learn-• Cells reproduce. • Certain cells reproduce in one way, while others reproduce in another. !

• You will learn and explain the steps of cell reproduction as well as the two types of cell reproduction.

• Go to cellsalive.com

Mitosis • Mitosis is the process of cell reproduction by making a copy of its chromosomes and then dividing.

• The new cells created are called daughter cells. • The original cell is called the parent cell. • Each daughter cell produced by mitosis has the same number and kind of chromosomes as the parent cell.

• If this process is not occurring in the cell, the chromosomes are invisible because they are long, thin, and spread out throughout the nucleus.

• http://www.youtube.com/watch?v=BhomXMKu7wU&safe=active

Mitosis• Mitosis is only for eukaryotic cells. !

• Prokaryotic cells reproduce in a process called binary fission.

• http://www.youtube.com/watch?v=2WwIKdyBN_s&feature=related

Type of Reproduction #1-Mitosis:• If a cell wants to make a duplicate of itself, it first must copy its

DNA (part of a chromosome in the nucleus that contains DNA). !

• The copies then must be separated & sorted into two sides of the cell. !• The cell then splits in two. Part of each parent is carried to the

two new cells, called daughter cells. !

• Results in cells such as internal organs, skin, bones, blood, etc. !

• A copy is made. This is how you have skin cells after you have a scrape as opposed to a new blood cell.

• http://www.youtube.com/watch?v=VlN7K1-9QB0 •

Mitosis: Meiosis:

Each resulting cell still has chromosomes from mom & dad http://www.youtube.com/watch?v=BhomXMKu7wU&safe=active

Interphase occurs just before Mitosis begins:• DNA is replicated along

with organelles and other cellular components and the cell prepares for division.

• The chromosomes that are copied are called chromatids.

• The chromatids are held together by centromeres in the middle.

• The chromosomes are visible because they have condensed.

http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

Mitosis Interphase

Animal cell Plant cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

1st step in Mitosis: Prophase (preparation phase)

• The DNA recoils, and the chromosomes condense.

• The nuclear membrane disappears, and the spindle fibers begin to form.

Mitosis Prophase

Animal cell Plant cell

2nd step in Mitosis:metaphase (organizational phase)

The chromosomes line up the middle of the cell with the help of spindle fibers attached to the centromere of each replicated chromosome.

Mitosis Metaphase Animal cell Plant cell

3rd step in Mitosis: Anaphase (separation phase)

The chromosomes split in the middle and the sister chromatids are pulled by the spindle fibers to opposite poles of the cell.

Mitosis AnaphaseAnimal cell Plant cell

4th step in Mitosis: Telophase

• In telophase, the nuclear membrane forms around the two sets of chromosomes. The chromosomes unwind, fibers disappear, and mitosis is complete.

• The chromosomes decondense.

Mitosis Telophase Animal cell Plant cell

After Mitosis: Cytokinesis

• The actual splitting of the daughter cells into two separate cells is called cytokinesis.

• It occurs differently in both plant and animal cells.

• The cytoplasm is split in two, and the result is two identical cells.

Beginning of cytokinesis in a plant:

Beginning of cytokinesis in an animal:

Mitosis-Look at it Again•Mitosis is the process in which the nucleus divides to form two identical cells.

•Process starts with one cell but results in two identical cells: 1 Parent Cell=2 Daughter Cells http://www.youtube.com/watch?v=pOsAbTi9tHw&safe=active

4 Phases of Mitosis

PMAT • Phase 1-Prophase • Phase 2-Metaphase • Phase 3-Anaphase • Phase 4-Telophase

Prophase=“Pairs”

• Chromosomes form pairs and duplicate (multiply). • During Prophase there are 46 PAIRS of

chromosomes.

Metaphase=“Middle”• Chromosomes line up in the middle of the cell.

Anaphase=“Apart”• Chromosomes are pulled apart by spindle fibers.

Telophase=“Twins/Two”• Cells divide and form two identical daughter cells. Early telophase Late telophase

Mitosis • Mitosis is the process by which living things grow. • For example, one bone cell divides and produces two

identical bone cells. • Each of these cells then divides to produce more bone

cells of the same kind. • The same process occurs in all living things. • Mitosis is the process by which the bodies of living things

repair themselves. • http://www.youtube.com/watch?

v=ZEwddr9ho-4&safe=active •

#2-Meiosis:• The second type of cell reproduction is meiosis. !

• As in mitosis, if a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome). !

• Results in reproductive cells-the sperm and the egg. !

• The cells are unique-not copies. !

• Part of each parent is carried to the four new cells. !

• Each new cells has half the number of chromosomes of the parent cell. !

• Meiosis involves two sets of divisions.

!!!!!!

• Meiosis is a special type of cell division necessary for sexual reproduction in eukaryotes.

• The cells produced by meiosis are gametes or spores. In many organisms, including all animals and land plants (but not some other groups such as fungi), gametes are called sperm and egg cells.

Meiosis!

•Meiosis animation: http://www.youtube.com/watch?v=D1_-mQS_FZ0&NR=1

Chromosomes and Chromosome Number

Meiosis – Homologous Chromosomes

Sexual Reproduction and Genetics

• Same length

▪Same centromere position▪ Carry genes that control

the same inherited traits

!▪ One is from mother, one

is from father = a matching set

The Importance of Meiosis

▪ Meiosis consists of two sets of divisions

Sexual Reproduction and Genetics

▪ Produces four haploid daughter cells that are not identical

Meiosis

▪ Results in genetic variation

Meiosis InterphaseMeiosis is preceded by interphase. !The chromosomes have not yet condensed. !This is what the cell looks like before.

http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Interphase The chromosomes have replicated, and the chromatin begins to condense. !This is the cell during interphase. !The t-like red things are the chromatids.

Meiosis Prophase IThe chromosomes are completely condensed. They are now rod-like structures. ! In meiosis (unlike mitosis), the homologous chromosomes pair with one another. So, they don’t split apart. Instead, they pair up.

Meiosis Metaphase I

The nuclear membrane dissolves and the homologous chromosomes (Pairs of chromosomes) attach to the spindle fibers.

They are preparing to go to opposite poles.

Meiosis Anaphase I The chromosomes move to opposite ends of the cell.

Meiosis Telophase I & Cytokinesis

The cell begins to divide into two daughter cells.

It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes.

Meiosis Prophase II The cell has divided into two daughter cells.

Meiosis Metaphase II As in Meiosis I, the chromosomes line up on the spindle fibers.

Meiosis Anaphase II The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell.

Telophase II & Cytokinesis With the formation of four

cells, meiosis is over. If this process happens in a

male, male reproductive cells are formed.

If it occurs in a female, female reproductive cells are formed.

Each new cell has only half the chromosomes needed.

When the male and female reproductive cells are joined, the fertilized cell will have a complete set of chromosomes.

Cells alive• Goggle cells alive • Click interactive mitosis • Click interactive meiosis • http://www.youtube.com/watch?v=p2tGquUvrBQ&safe=active

• https://www.youtube.com/watch?v=pOsAbTi9tHw

Or, how doughnuts are made….

9-Cell Division and Mitosis lesson 9 -...

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