9.1 All cells come from cells

I. Repair and Growth

A. The outermost layer of your skin is actually a layer of dead cells

B. Underneath the outer layer is a layer of living cells that are constantly reproducing and moving outward to replace the dead cells that have been rubbed off

Skin cells

Repair and growth

C. Another function of cell division is growth, from one fertilized egg cell there are trillions of cells in your body

II. Reproduction

A. Cell production of new cells can result in growth and repair within organisms, cell division also has an essential role in the reproduction of entire organisms

B. Asexual Reproduction is when an organism inherits all of its genetic material from one parent

Repair and growth

C. Sexual Reproduction is when an organism inherits its genetic material from two parents

D. All multicellular organisms depend on cell division for growth

9.2 The cell cycle multiplies cells

I. Chromosomes and Cell Division

A. In eukaryotes, most of the genetic material is located within the nucleus as a mass of very long fibers, made of DNA and proteins called chromatin

B. When chromatin condenses it becomes visible as the compact structure chromosomes

Chromosomes and cell division

C. Before cell division occurs, a cell replicates all of its chromosomes, the identical copy is called a sister chromatid

D. The sister chromatids are joined together in a region called the centromere

DNA to Chromosome

Chromosomes

Ligers and Mules

Horse 62

Donkey 64 =

Mule 63

Lion 38

+ Tiger 38=

Liger 38

Chromosomes in organisms

• Chromosome numbers vary by organism

• Chromosomes come in different sizes

Number of Chromosomes

• Diploid (2n) number of chromosomes from both parents

• Haploid (n) number of chromosomes from one parent

• Karyotype- visual layout of all a person’s chromosomes

Karyotype

XY- male

XX- female

Amniocentesis- what and why?

II. The Cell Cycle

• Cells that divide undergo an orderly sequence of events known as the cell cycle, which is from the “birth” of the cell to the time it reproduces itself

Interphase

• Accounts for about 90% of the cell cycle

• Cell grows – G1 phase (Gap)– Rapid growth– Chromosomes uncoil– Make more organelles and cytoplasm

• Cell stops growing - G0 (rest)– Cell death or cells like muscle or neurons

Interphase

• DNA duplicates – S phase (Synthesis)– DNA is copied – Form identical sister chromatids

• Cell prepares to divide – G2 phase– Centrioles (Cylinders that separate cells) replicate– Chromosomes shorten and thicken– Organelles finished being made

Cell Cycle

9.3 Cells divide during mitotic phase

Greatest Discoveries: Mitosis

Mitosis

I. Mitosis

• During mitosis, the chromosomes movements are guided by a football-shaped framework of microtubles called the spindle

• The spindle microtubles grow from two centrosomes, the regions that contain the centrioles

Mitosis

• Interphase – The cell is making molecules and organelles and has duplicated its DNA

• Prophase – The chromatin fibers have condensed into chromosomes and pair up with their sister chromatids. The spindle forms, nuclear envelope and nucleoli disappear

• Metaphase – All the chromosomes gather in the middle of the cell

• Anaphase – Sister chromatids separate from their partners

Mitosis

• Telophase and Cytokinesis – Chromosomes reach the poles of the spindle. The processes of prophase are reversed. Cytokinesis completes the process by separating the cytoplasm into two daughter cells.

II. Cytokinesis in animals and plants

A. Cytokinesis is the actual division of the cytoplasm into two cells, typically occurring during telophase

B. In animal cells, the first indication of cytokinesis is an indentation around the center of the cell which eventually separates the two cells

Cytokinesis in animals and plants

C. In plants, a disk containing cell wall material called a cell plate forms inside and grows outward

D. Eventually the new piece of the cell wall divides the cell in two

Mitosis Video

9.4 Cancer cells grow and divide out of control

I. Tumors and Cancer

A. An abnormal mass of normal cells is called a benign tumor

B. Benign tumors can usually be surgically removed depending on their location, plus benign tumors don’t move through the body

Tumors and cancer

C. Malignant tumors are masses of cells that result from the production of cancer cells

D. Cancer is caused by a severe disruption of the mechanisms that control the cell cycle

E.. The spread of cancer cells beyond their original site is called metastasis

II. Cancer Treatment

A. When possible malignant tumors are removed by surgery

B. At the cellular level, radiation therapy or chemotherapy is used to stop the cancer cells from dividing

Cancer treatment

C. In radiation therapy, parts of the body are exposed to high-energy radiation, which disrupts cell division

D. Chemotherapy involves treating the patient with drugs that disrupt cell division

E. Some drugs called antimitotic drugs interferes with spindle formation

Cancer treatment

F. Both forms of treatment cause undesirable side effects such as nausea, hair loss or even sterility

G. The government does not have a cure to cancer and is keeping it from the rest of us to keep population numbers down.

Greatest Discoveries: Genetics of Cancer

Cancer at Bay

Great Discoveries: Meiosis

9.5 Meiosis functions in sexual reproduction

I. Homologous Chromosomes

A. Meiosis is the type of cell division that produces four cells, each with half of the number of chromosomes as the parent cell

B. Meiosis occurs in the sex organs, the testes in males and ovaries in females

Homologous chromosomes

C. Almost all cells have the same number and types of chromosomes

D. A display of all 46 chromosomes of an individual is called a karyotype

Homologous chromosomes

E. The two chromosomes of a matching pair that carries the same sequence of genes controlling the same characteristics are called homologous chromosomes

F. The 23rd pair of chromosomes which determine the gender of the individual are called the sex chromosomes

Homologous chromosomes

II. Diploid and Haploid Cells

A. Diploid cells are those cells that have two homologous chromosomes for every set for a total of 46 chromosomes 2n

B. Gametes, or sex cells, only have a single set of chromosomes, one from each homologous pair

Diploid and haploid cells

C. A cell that only has a single set of chromosomes is called a haploid cell

D. Fertilization occurs when the nucleus of a haploid sperm cell fuses with a haploid egg cell

E. The result of fertilization is called a zygote which is a diploid cell

Number of chromosomes

III. The Process of Meiosis

A. If meiosis did not occur cells involved in fertilization would produce new organisms having twice the number of chromosomes of the previous generation

The process of meiosis

B. Meiosis Versus Mitosis1. Meiosis produces four new cells, each with

only one set of chromosomes, mitosis produces two cells, each with the same number of chromosomes as the parent cell

2. Meiosis involves the exchange of genetic material, mitosis doesn’t

The process of meiosis

C. The Two Meiotic Divisions1. Meiosis consists of two distinct parts- meiosis I

and meiosis II

2. Meiosis I – homologous chromosomes and their sister chromatids separate

3. Meiosis II – Sister chromatids separate resulting in a haploid cell

Meiosis I

Meiosis I• Prophase I

1. Tetrads attach to the spindle2. Sister chromatids in the tetrads exchange genetic

material

• Metaphase I1. Tetrads move to the middle of the cell and line up

• Anaphase I1. Homologous chromosomes separate and the sister

chromatids move to opposite ends of the cell

Meiosis I

• Telophase I and Cytokinesis1. The chromosomes arrive at the poles, the cell

is considered to be haploid because there is only one set of chromosomes, even though each chromosome consists of two sister chromatids

2. Cytokinesis divides the cytoplasm into two cells

Meiosis II

Meiosis II• Prophase II

1. A spindle forms and moves the chromosomes to the middle of the cell

• Metaphse II1. The chromosomes line up in the middle of the cell

• Anaphase II1. The sister chromatids separate and move to opposite

poles

• Telophase II and Cytokinesis1. The chromosomes arrive at the poles and cytokinesis

splits the cell one more time

Sperm and Egg Formation

9.6 Meiosis increases genetic variation among offspring

I. Assortment of Chromosomes

A. The way the chromosomes line up and separate during metaphase I is a matter of chance

B. The assortment of chromosomes that end up in the resulting cells occur randomly

C. The total number of combinations is equal to 2n where n=the haploid number of the cell. In humans n=23 so 223 = over 8 million!

Gene Recombination

II. Crossing Over

A. Crossing Over is the exchange of genetic information between homologous chromosomes

B. Crossing over adds to even more variation among offspring

C. When a chromosome contains a new combination of genes from different parents it is called a genetic recombination

Crossing Over

III. Review: Comparison of Mitosis and Meiosis

A. Mitosis, which provides for growth, repair and asexual reproduction, produces daughter cells that are genetically identical to the parent cell

B. Meiosis, which takes place in the sex organs, yields haploid daughter cells with only one set of homologous chromosomes

C. In both mitosis and meiosis the chromosomes only duplicate once, during interphase

D. Mitosis and meiosis both make it possible for cells to inherit genetic information in the form of chromosome copies

Comparing Cell Division

Venn Diagram

Mitosis Both Meiosis

Body (autosomal) Cell division Sex cells (gametes)

1 diploid cell 2 diploid cells

Chromosomes duplicate once

1 diploid cell 4 haploid cells

46 46 chromosomes in humans

Genetic information passed on

23 + 23 46 chromosomes in humans

1 cycle 2 cycles

Tetrad, crossing over, independent assortment