Cell Cycle. **The cell cycle or the cell division cycle is a series of events that take place when a cell is going to divide and reproduce a new cell

Cell CycleCell Cycle

**The cell cycle or the cell division cycle is a **The cell cycle or the cell division cycle is a series of events that take place when a cell series of events that take place when a cell is going to divide and reproduce a new cell. is going to divide and reproduce a new cell. This process must take place when:This process must take place when:1.1. A fertilized egg develops into a multicellular A fertilized egg develops into a multicellular

organismorganism2.2. An organism must replace cells that have An organism must replace cells that have been injured or destroyedbeen injured or destroyed3. An organism grows3. An organism grows

There are 2 main parts to this cycle:There are 2 main parts to this cycle:1.1. Interphase Interphase 2.2. Mitotic phase (M phase)Mitotic phase (M phase)

SCI.9-12.B-2SCI.9-12.B-2 - [Standard] - The student - [Standard] - The student will demonstrate an understanding of the will demonstrate an understanding of the structure and function of cells and their structure and function of cells and their organelles.organelles.

SCI.9-12.B-2.6SCI.9-12.B-2.6 - [Indicator] - Summarize - [Indicator] - Summarize the characteristics of the cell cycle: the characteristics of the cell cycle: interphase (called G1, S, G2); the phases interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and anaphase, and telophase); and plant and animal cytokinesis.animal cytokinesis.

ChromosomesChromosomes

**

Homologous chromosomes – Homologous chromosomes – Chromosomes that have the same type of Chromosomes that have the same type of gene located at the same spot (locus). You gene located at the same spot (locus). You inherit one from your mom and one from inherit one from your mom and one from your dad. They both give you a number your dad. They both give you a number one chromosome but dad’s might have a one chromosome but dad’s might have a gene for brown eyes and mom’s a gene for gene for brown eyes and mom’s a gene for green eyes. Alleles – different forms of green eyes. Alleles – different forms of same genesame gene

**

Humans have 23 pair of chromosomes. Humans have 23 pair of chromosomes.

22 pair of autosomes determine 22 pair of autosomes determine characteristics characteristics

The 23The 23rdrd pair determines the sex of the pair determines the sex of the child child XX = femaleXX = female

XY = maleXY = male

**

Genes that are found on the same Genes that are found on the same chromosome are said to be chromosome are said to be linkedlinked and and are inherited together. For example, red are inherited together. For example, red hair and freckles are on the same hair and freckles are on the same chromosome and are usually inherited chromosome and are usually inherited together.together.

Structure of a chromosomeStructure of a chromosome

*Chromatids are *Chromatids are

connected by the connected by the

centromerecentromere and and

have a have a LONG AND LONG AND

SHORT ARMSHORT ARM. .

p = short armp = short arm

q = long armq = long arm

The ends of the armsThe ends of the arms

are called are called telomerestelomeres..

Involved in agingInvolved in aging

Chromatids are connected by the centromere and have a LONG AND SHORT ARM.

p arm

q arm

telomerethe entireia a

chromatid

**

Centromeres and telomeres are made of Centromeres and telomeres are made of short sections of DNA repeated over and short sections of DNA repeated over and over. over.

For example, AAATTT AAATTT For example, AAATTT AAATTT AAATTT AAATTT.AAATTT AAATTT.

*INTERPHASE*INTERPHASE

Interphase is when the cell is obtaining Interphase is when the cell is obtaining nutrients, growing, and making new nutrients, growing, and making new cellular parts. Inter phase is sometimes cellular parts. Inter phase is sometimes called the “resting stage” but it does not called the “resting stage” but it does not rest here. Interphase has 3 parts:rest here. Interphase has 3 parts:

GG11 – Growth 1 – Growth 1

S phase -- when DNA copies itselfS phase -- when DNA copies itself

GG22 – Growth 2 the cell is getting ready – Growth 2 the cell is getting ready

to divideto divide

Plant cell in interphasePlant cell in interphase


*Prophase*Prophase Second stage of cell cycle – the first in Second stage of cell cycle – the first in

the M phasethe M phase Everything that appears in this phases Everything that appears in this phases

will disappear in telophase. Everything will disappear in telophase. Everything that disappeared here will re-appear in that disappeared here will re-appear in telophasetelophase

*Prophase continued*Prophase continued1. Chromatin condenses (shortens) into 1. Chromatin condenses (shortens) into chromosomeschromosomes

2. Centrioles start moving toward poles (ends 2. Centrioles start moving toward poles (ends of cell).of cell).

3. Mitotic spindle begins to form.3. Mitotic spindle begins to form.

4. The nucleolus disappears.4. The nucleolus disappears.

5. The nuclear membrane disappears.5. The nuclear membrane disappears.

6. Mitotic spindle is fully formed with 6. Mitotic spindle is fully formed with chromosomes attached to its fibers. And the chromosomes attached to its fibers. And the chromosomes are all moving toward the chromosomes are all moving toward the center of the cell (called equator).center of the cell (called equator).

*Metaphase*Metaphase

In metaphase, all the chromosomes have In metaphase, all the chromosomes have their centromeres lined up on the their centromeres lined up on the equator.equator.


Plant cell in metaphasePlant cell in metaphase

*Anaphase*AnaphaseIn anaphase, the centromere divides and In anaphase, the centromere divides and

separates the two chromtids. They are separates the two chromtids. They are now called chromosomes and they move now called chromosomes and they move away from the equator toward the poles. away from the equator toward the poles. (Think A = Away A = anaphase)(Think A = Away A = anaphase)

Plant Cell in AnaphasePlant Cell in Anaphase


*Telophase*TelophaseTelophase is the last stage of mitosis and it Telophase is the last stage of mitosis and it

is the opposite of prophase. Whatever is the opposite of prophase. Whatever appeared in prophase, will disappear in appeared in prophase, will disappear in telophase and whatever disappeard in telophase and whatever disappeard in prophase will reappear in telophase.prophase will reappear in telophase.

1. Chromosomes go back to chromatin.1. Chromosomes go back to chromatin.

2. Mitotic spindle disappears.2. Mitotic spindle disappears.

3. Nucleolus reforms.3. Nucleolus reforms.

4. Nuclear membrane reforms4. Nuclear membrane reforms

Plant Cell in telophasePlant Cell in telophase

*Cytokinesis*CytokinesisAfter the nucleus finishes dividing, the After the nucleus finishes dividing, the cytoplasm has to divide. It divides evenly cytoplasm has to divide. It divides evenly down the middle so that the 2 new cells down the middle so that the 2 new cells are the same size. are the same size.

In plant cells, the cell wall begins to form In plant cells, the cell wall begins to form first. Then the cell membrane divides.first. Then the cell membrane divides.

Cytokinesis in plant cellsCytokinesis in plant cells

*How long does it take *How long does it take for cells to divide?for cells to divide?

The more complicated a cell is the longer The more complicated a cell is the longer it takes to divide. Your skin cells take it takes to divide. Your skin cells take about 10 hours to divide. Some cells in about 10 hours to divide. Some cells in your body do not divide at all. For your body do not divide at all. For example, your brain cells are in the example, your brain cells are in the GG00

phasephase, meaning they do not divide. Your , meaning they do not divide. Your muscles will not divide again unless they muscles will not divide again unless they are damaged in some way.are damaged in some way.


Cells Undergoing MitosisCells Undergoing Mitosis

Interphase Prophase

Metaphase Anaphase

Telophase

Documents

Cell Cycle. **The cell cycle or the cell division cycle is a series of events that take place when a cell is going to divide and reproduce a new cell