The Cell Cycle, Mitosis & Cell Division Omnis cellula e cellula Chapter 9 Biology In Focus AP Biology 2014 Ms. Eggers

Why? From fertilization to arrival of baby, to adulthood, we grow from one cell into trillions of cells. Why? From fertilization to arrival of baby, to adulthood, we grow from one cell into trillions of cells. Why? Why aren ’ t we just one big cell? What limits cell size? Why aren ’ t we just one big cell? What limits cell size? What are the functions of cell division? What are the functions of cell division? Reproduction Reproduction Growth and development Growth and development Tissue repair and renewal Tissue repair and renewal Regeneration Regeneration

Each of our cells is the same in one way… Every single cell in our body has the exact same set of genes – the blue print for making an entire new organism (which gives rise to the idea that someone could make a clone of you from a few of your skin cells). Every single cell in our body has the exact same set of genes – the blue print for making an entire new organism (which gives rise to the idea that someone could make a clone of you from a few of your skin cells). The entire set of DNA in an organism is called its genome. The entire set of DNA in an organism is called its genome.

Division requires duplication Every time a cell grows and divides, it must duplicate this set of blue prints (its genome), so that each of the two cells produced (called daughter cells) gets an EXACT copy of what the parent cell originally had. Every time a cell grows and divides, it must duplicate this set of blue prints (its genome), so that each of the two cells produced (called daughter cells) gets an EXACT copy of what the parent cell originally had. This process of duplicating the genetic blue print and then dividing into two new cells is called cell division. This process of duplicating the genetic blue print and then dividing into two new cells is called cell division.

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

How is the DNA organized within our cells? The genetic information of a eukaryotic organism is stored in the nucleus of the cell. The genetic information of a eukaryotic organism is stored in the nucleus of the cell.

Within the nucleus are found chromosomes… Chromosomes are composed of chromatin, which is a long, coiled strand of DNA and some proteins to help with structure. Chromosomes are composed of chromatin, which is a long, coiled strand of DNA and some proteins to help with structure. That long strand of DNA contains thousands of genes – each gene contains the information to make just one protein. That long strand of DNA contains thousands of genes – each gene contains the information to make just one protein.

Chromosome structure One arm of a duplicated chromosome

Where do we get our genes? Well, from Mom and Dad… Well, from Mom and Dad… So we have 2 copies of every gene – one from Mom and the other from Dad (a good back-up!) So we have 2 copies of every gene – one from Mom and the other from Dad (a good back-up!) Therefore, we have 2 copies of every chromosome in our nucleus. Therefore, we have 2 copies of every chromosome in our nucleus. One pair of alike chromosomes are called homologous chromosomes. One pair of alike chromosomes are called homologous chromosomes.

We have 46 chromosomes in every somatic (body) cell… or 23 pairs. Two copies of chromosome # 1, # 2, # 3, etc. Two copies of chromosome # 1, # 2, # 3, etc. There are 22 pairs of numbered chromosomes – called autosomes. There are 22 pairs of numbered chromosomes – called autosomes. The last pair are called sex chromosomes. The last pair are called sex chromosomes. If your are female, you have two copies of the X chromosome. If your are female, you have two copies of the X chromosome. If you are male, you have one X chromosome and one Y chromosome. If you are male, you have one X chromosome and one Y chromosome.

Our body cells are diploid. Because our cells have 2 copies of each type of chromosome, we refer to them as diploid – and would write this as 2N. Because our cells have 2 copies of each type of chromosome, we refer to them as diploid – and would write this as 2N. Reproductive cells, called gametes, only have one copy of each chromosome (we ’ ll talk about these later). We call these cells haploid – and write this N. Reproductive cells, called gametes, only have one copy of each chromosome (we ’ ll talk about these later). We call these cells haploid – and write this N.

Different organisms have a different number of chromosomes. The number of chromosomes an organism has bears no relation to its “ complexity. ” The number of chromosomes an organism has bears no relation to its “ complexity. ” Having a different diploid number is also one of the reasons that members of different species cannot mate and produce fertile offspring. Having a different diploid number is also one of the reasons that members of different species cannot mate and produce fertile offspring. Organism Diploid Chromosome # Human46 Dog78 Cat38 Horse64

Cell division A parent cell divides into 2 daughter cells. A parent cell divides into 2 daughter cells. Then each daughter cell can divide again to form 2 daughter cells of their own. Then each daughter cell can divide again to form 2 daughter cells of their own. Before division, a cell must grow, and it must duplicate its chromosomes. Before division, a cell must grow, and it must duplicate its chromosomes.

From the time a daughter cell is “ born ” and divides again is called the cell cycle. Cytokinesis: when the membrane divides the cell into 2 separate cells

Parts of the cell cycle Cytokinesis: the division of the membrane and cytoplasm into two daughter cells Cytokinesis: the division of the membrane and cytoplasm into two daughter cells Interphase: the cell grows, produces proteins and cytoplasmic organelles Interphase: the cell grows, produces proteins and cytoplasmic organelles G 1 phase – the phase when cells are “doing their job” G 1 phase – the phase when cells are “doing their job” S phase – chromosomes duplicate S phase – chromosomes duplicate G 2 phase – completes preparations for cell division G 2 phase – completes preparations for cell division Mitosis: the division of the genetic material in the nucleus Mitosis: the division of the genetic material in the nucleus

What occurs in each stage of mitosis? During the S phase, the chromosomes have been duplicated… During the S phase, the chromosomes have been duplicated… In G2 there are now centrosomes, which are the regions where the microtubule spindles are organized In G2 there are now centrosomes, which are the regions where the microtubule spindles are organized

Prophase: Prophase: Chromosomes condense Chromosomes condense Sister chromatids become apparent Sister chromatids become apparent Nucleoli disappear Nucleoli disappear Mitotic spindle forms, centrosomes appear as asters and begin to separate Mitotic spindle forms, centrosomes appear as asters and begin to separate Prometaphase: Prometaphase: Nuclear membrane fragments Chromosomes become even more condensed Kinetochores form at the centromere of each chromosome Mitotic spindles now extend across the cell and meet Microtubule spindles attach to the kinetochores

Prophase Prometaphase

Metaphase: Metaphase: Chromosomes line up in “single file” on the metaphase plate Chromosomes line up in “single file” on the metaphase plate Centrosomes are at either side of the cell Centrosomes are at either side of the cell Kinetochore microtubules are connected to each chromosome at the centromere Kinetochore microtubules are connected to each chromosome at the centromere Anaphase: Anaphase: Cohesion proteins holding the two sister chromatids together at the centromere are cleaved The mitotic spindles begin to shorten, pulling each new individual daughter chromosome to opposite ends of the cell This is the shortest phase

Metaphase Anaphase

Telophase Telophase Two nulcei reform Two nulcei reform Nucleoli reappear Nucleoli reappear Chromosomes decondense Chromosomes decondense Mitotic spindles disassemble and disappear Mitotic spindles disassemble and disappear Cytokinesis Cytokinesis In animal cells this involves the development of a cleavage furrow created by a ring of microfilaments In plant cells, a cell plate forms between the two daughter cells and eventually becomes the new cell wall

Telophase Cytokinesis

Mitosis Animations, etc. Mitosis video 1 (6:20) Mitosis video 1 (6:20) Mitosis video 1 Mitosis video 1 Mitosis Rap (3:17) Mitosis Rap (3:17) Mitosis Rap Mitosis Rap

Binary Fission in Bacteria Reproduction in bacteria involves duplicating their bacterial chromosome, enlarging, and dividing Reproduction in bacteria involves duplicating their bacterial chromosome, enlarging, and dividing It does NOT involve the exchange of genetic material that occurs in eukaryotic sexual reproduction It does NOT involve the exchange of genetic material that occurs in eukaryotic sexual reproduction The new bacterium is identical to the original bacterium The new bacterium is identical to the original bacterium

Videos of actual mitosis (tutorial videos can be found on my Weebly site) Mitosis in developing sea urchin cells Mitosis in developing sea urchin cells Mitosis in developing sea urchin cells Mitosis in developing sea urchin cells Contrast microscopy video of mitosis Contrast microscopy video of mitosis Contrast microscopy video of mitosis Contrast microscopy video of mitosis Fluorescent microscopy video of mitosis in early developing fruit fly embryo Fluorescent microscopy video of mitosis in early developing fruit fly embryo Fluorescent microscopy video of mitosis in early developing fruit fly embryo Fluorescent microscopy video of mitosis in early developing fruit fly embryo Binary fission in bacteria video Binary fission in bacteria video Binary fission in bacteria video Binary fission in bacteria video