Cell Growth and DivisionI. Limits to Cell Growth

A. Why do cells divide? Instead of dividing, why don’t cells just grow larger and larger?

There are two main reasons why cells divide rather than continuing to grow larger and larger:

1. The larger a cell becomes, the:

2. If the cell grows too large, it will have trouble:

B. Problem #1: Our DNA has its limits!1. All of the _____________ that a cell needs to function is stored in the DNA of the cell.

2. DNA is packaged into _______________. A chromosome consists of one:

3. Each gene is the instructions for making a particular __________ that the cell needs.

4. The cell is constantly ________________ of these genes and sending the copies (in the form of RNA) out to the _______________.

5. When the cell is small, the information stored in the cell’s DNA is adequate to meet the needs of the cell.

6. As the cell grows too large, there is an “information crisis”. The DNA cannot keep up with:

C. Problem #2: A Growing Cell Needs More Food!1. A cell must take in a constant inflow of ____________________________________ across the

membrane.

2. ____________________ must constantly be crossing the membrane in order to leave the cell.

3. A larger cell will require much more food, oxygen and water. A larger cell will generate much more waste.

4. As the cell grows, the __________ of the cell increases much more rapidly than the ________________ of the cell membrane.

5. When the cell gets too large, the membrane surface area is not adequate enough to:

Copyright © Science Stuff

II. Cell division1. Cell division is the process by which cellular material is divided:

1

2. 1 Mother Cell ---> 2 Daughter cells. The two daughter cells will be:

3. Each daughter is half the size of the parent cell, but immediately begins growing.4. A typical human cell has about 2 meters of DNA. Before the cell can divide, all of this

DNA must be _________ and then the two copies separated so that each daughter cell ends up with _______________________________.

5. Each species has a characteristic number of chromosomes in each cell nucleus; humans have ___________________.

III. Chromosomes During Eukaryotic Cell DivisionA. Each cell must first ______________________

before cell division occurs.B. Each daughter cell gets a complete copy

of that information.C. Cell division occurs in two main stages:

1. Mitosis –

2. Cytokinesis –

D. The chromosomes are not visible except duringcell division. At the beginning of cell division,the chromosomes:

E. Well before cell division takes place, each chromosome is replicated or copied.

F. At the beginning of cell division, each chromosome consists of two identical “__________________________.” These chromatids are connected at an area called a __________________.

Copyright © Science Stuff

IV. The Cell Cycle1. The cell cycle is:

2. The cell cycle is the life of the cell from the time it is first formed from a dividing parent cell until its own division into two cells.

3. During the cell cycle:

2

4. The cycle consists of five major phases:

a)b)c)d)e)

5. Before a cell can begin mitosis and actually divide, it must do two things:a)

b)

6. These preparations occur during the _________________ phases of the cell cycle.

7. These three are collectively known as ______________.

8. G1 phasea)

b)

9. S Phasea)

10. G2 Phasea)

Copyright © Science Stuff11. When interphase (G1, S, G2) is complete, the cell is ready to begin the process of cell

division. 12. Interphase

(a) Of the cell cycle, interphase accounts for 90% of the time. (b) Nucleus is _____________ and bounded by the ________________________.

3

(c) Outside of the nucleus are two _____________. Their function is to:

They will begin to move apart as spindle microtubules grow out of them.

(d) G1 phase is a period of intense biochemical activity:

(e) The chromosomes have ____________ during the S phase and they appear as a jumbled mass of fibers. They have not yet condensed.

(f) G2 Phase:

V. Mitosis

A. Has 4 Stages1.

2.

3.

4.

Copyright © Science StuffB. Stages of Mitosis

1. Prophase

Early prophase Late prophase

Early Prophase:(a) The chromosomes coil and thicken and become ____________ from one another. The

chromosomes are now visible.

(b) The nucleolus ____________________.

(c) The chromosomes are:

(d) Each half of the double chromosome is a _____________________.

4

(e) The chromatids are connected by a __________________.

(f) The _____________ separate and start moving to opposite ends of the cell. A ____________ made of ________________ begins to form.

Late Prophase:(g) The __________________ fragments and the microtubules invade the nuclear area.

The spindle is completely formed.

(h) The spindle is a structure that will help to ________________________________. During prophase the pairs of _____________ become attached to the fibers of the spindle.

(i) The centrioles have moved to the opposite poles, forming the spindle as they go.

Copyright © Science Stuff

2. Metaphase

(a) The centrioles: (b) The spindle fibers will:

(c) The chromosomes:

(d) Each chromosome is connected to a spindle fiber at its centromere.

3. Anaphase

(a) The centromeres divide and:5

(b) The microtubules begin to:

(c) By the end of anaphase, the two ends of the cell have:

Copyright © Science Stuff4. Telophase

(a)

(b)

(c)

VI. CytokinesisA. At the end of mitosis, ________________ have been formed. Each nucleus has an

identical set of _________________.

B. Cytokinesis is:

C. Cytokinesis usually occurs at the same time as telophase.

D. In animal cells, a ___________________ pinches the cell membrane inward until the cell is pinched into two separate cells. Each new cell contains its own nucleus, cytoplasm, and organelles.

E. In plants, it is _______________ for the cell to pinch inward because of the rigid ______________. In plants, a _____________ forms midway between the two nuclei. The cell plate continues to form across the cell until two separate cells have been formed.

6

Copyright © Science Stuff

VII. The Importance of the Cell Division ProcessA. Mitosis

1. Takes between 30 minutes and 2 hours.2.

3. The two daughter cells:

B. Results of Mitosis1. In unicellular plants and animals:

2. In multicellular organisms:

C. Importance of Mitosis1. The two new cells are exact __________________.2. This insures that:

VIII. Regulation of the Cell Cycle A. The frequency of cell division varies with the type of cell. ________________ divide

frequently throughout our lives. ________________ maintain the ability to divide but only do so on rare occasion - say to repair a wound. The most specialized cells, such as ______________________ cells, do not divide at all.

B. Controls on Cell Division1. When cells come into contact with other cells, they respond by __________________.2. When an injury, like a cut in the skin occurs, the cells at the edge of the injury

begin to: ______________________.3. When the healing process nears completion, the rate of cell division slows down.

C. Cell Cycle Regulators1. There are many ____________ found on the inside and the outside of the cell that

regulate cell division. 2. Some of these proteins are responsible for:

. 3. Other proteins seam to ________________________the cell division process.4. These proteins send out ____________ that prevent excessive cell growth. This

keeps the tissues of the body from disrupting one another.

Copyright © Science Stuff

7

D. Uncontrolled Cell Growth1. If the cells in a tissue grow uncontrollably, the consequences may be severe.2. ________________ do not respond to the signals that ___________ the growth of cells.

Cancer cells divide ______________ and form masses of cells called ___________. These tumors can __________ the surrounding healthy tissues.

3. All cancers have one thing in common:

Meiosis and Sexual Reproduction

I. Asexual and Sexual ReproductionA. Asexual Reproduction

1.

2. Advantages of Asexual Reproduction(a)

(b)

(c)

3. Disadvantage of Asexual Reproduction(a)

(b)

B. Sexual Reproduction1.

2. Must have male and female: male to produce sperm and female to produce eggs.3. Disadvantages:

(a)

(b)

(c) Copyright © Science Stuff

4. Advantage:(a)

5. Sexual reproduction always involves:(a) gametes:

8

(b) fertilization: (c) zygote:

II. Cell Division and Chromosome NumberA. If an organism is the result of sexual reproduction, it will have _____ sets of

chromosomes. One set comes from the __________ and one set comes from the _______.

B. These two sets are called ________________________________.

C. Homologous chromosomes are:

D. Homologous chromosomes carry the same _______, but they may have different ________________of that gene.

E. Diploid1. Diploid means that:

2.

3. Diploid cells contain:

4. So in mitosis:

Copyright © Science StuffF. Chromosome number in gametes

1. ________________ cells must have _______ the number of chromosomes so that when added together, the ______________ will have the proper number.

2. Example: human body

3. Gametes are said to be ____________________ because they contain only ______ of each kind of chromosome.

4. The cells, which produce eggs, and the cells, which produce sperm, are diploid or 2N. So how do the egg and sperm cells get to be 1N? ___________________

9

5. Meiosis is a process of:

III. Phases of MeiosisA.

B. Purpose is to:

C. Meiosis, like mitosis, is preceded by the replication of chromosomes. Unlike mitosis, this replication is then followed by two divisions:

Copyright © Science StuffD. Drawings of the stages of meiosis

10

E. Stages of Meiosis1. Interphase: The ____________ replicate. It is similar to chromosome replication of

mitosis. Two identical sister chromatids are held together by a centromere.

2. Prophase I: Chromosomes ______________________. Each chromosome pairs with its corresponding homologous chromosome to form a _________. There are _______________ in a tetrad.

3. Metaphase I:

4. Anaphase I:

5. Telophase I and Cytokinesis: a)

b)

c)

6. Prophase II: The pairs of sister chromatids start toward the center.

7. Metaphase II: 11

8. Anaphase II:

9. Telophase II and Cytokinesis:

F. Importance of Meiosis1.

2. The chromosome number of the egg and sperm is cut in half to insure that the zygote will have the proper number of chromosomes.

Copyright © Science StuffG. “Crossing Over” During Meiosis

1. During ______________, each pair of chromatids lines up next to its _____________.2. This pairing of homologous chromosomes produces ___________.

3. A tetra consists of ___________________.

4. It is possible for the chromatids within a homologous pair to twist around one another. Portions of the chromatids may:

5. This process is called “_________________”.

6. “Crossing over” is the exchange of _________________________________ between segments of homologous chromosomes during meiosis.

7. The result is that the offspring will receive __________________ of genetic information. This leads to ________________ in the offspring.

8. Variation leads to _________________________. These variations will cause some of the offspring to be _________________ for their particular environment. If they are better suited for their environment, it is _________________ that they will __________ to reproductive age and pass these favorable variations on to their offspring.

9. If the result of crossing over causes the offspring to be less suited for its environment, it may not _____________. Or, if the offspring does survive, it may not be reproductively competitive. This means that it may not be able to secure a mate. These “unfavorable” genes are _________________ to be passed on to the offspring.

12

10. Crossing over leads to _______________.

Copyright © Science Stuff

IV. Gamete FormationA. Meiosis produces __________________ cells that are different.

B. In males, meiosis results in:

C. In females, ___________ are produced, but only one will become an ______ cell. All of the ______________ and all of the _____________ are put into one egg cell. The other three cells:

V. Comparison of Mitosis and Meiosis A. Mitosis occurs in all cells of the ______ except ________________. Meiosis only occurs in

the formation of _______________________.

B. In meiosis, each __________ cell divides _______ to produce a total of _______ cells. In mitosis each _________ cell divides ________ to form _____ cells.

C. In meiosis, each of the four cells contains _______ the number of chromosomes as the parent cell. In mitosis, each new cell contains the _______ number of chromosomes as the original cell.

D. In mitosis, the homologous pairs do not come together to form ___________. In meiosis, the homologous pairs do come together to form __________. While the chromosomes are in tetrads, __________________ may occur. There will be no crossing over in ________________.

E. In meiosis, the four haploid cells contain _______________ combinations of chromosomes from each other. In mitosis, the new cells contain _____________ copies.

13

Copyright © Science Stuff

14