cell growth and division honors biology chapter 10

Cell Growth and Division

Honors Biology

Chapter 10

Cell Growth

Living things grow larger due to an increase in cells

Larger the cell, the more demands on the DNA and the more transport of water and nutrients across the membrane

The surface area to volume ratio must also be maintained.

Cell GrowthBefore the cell gets too big in size, it must

divide into 2 new daughter cells via a process known as cell division

In order to divide, the cell must make a copy of its DNA so each cell has a set of instructions of how the body functions

DNA Replication

Cell Division

Occurs in 2 main stages

1. mitosis – division of nucleus

2. cytokinesis – division of cytoplasmConsidered to be asexual since the two

daughter cells are genetically identical to the parent cell

Source of new cells as organism grows and develops

Chromosomes

Made of DNA and proteinsCells of every organism have a specific

number of chromosomes

humans = 46 carrot = 18 fruit fly = 8Chromosomes are only visible during cell

division, these structures form to compact the DNA to make it easy to divide

Chromosome Structure Each chromosome consists of 2 identical “sister” chromatids When the cell divides, the sister chromatids separate from

each other. One chromatid goes to each of the 2 new cells Each pair of chromatids are attached by the centromere. The

centromere is usually located near the middle of the chromatid The human body contains 46 chromosomes and 46

centromeres, each of which contain 2 chromatids

Short arm

Long arm

One chromosome with 2 identical sister chromatids

Cell Cycle

During the cell cycle, a cell grows, prepares for division, and divides to form 2 new identical daughter cells, each of which then begin the cycle again.

The cell cycle consists of 4 phases

1. M Phase: (mitosis phase) mitosis and cytokinesis

2. G1 Phase: (gap phase) growth and activity 3. S Phase: (synthesis phase) DNA replication

4, G2 Phase: (gap phase) growth and activity G1, S and G2 all used to be group together and

called interphase

Cell Cycle

M Phase

G1 Phase

S Phase

G2 Phase

Interphase

Cell spends more time in interphase than M phase

1. G1 Phase – Most growing occurs. Cells increase in size and synthesize new proteins and organelles

2. S Phase – Chromosomes are replicated. Key proteins are synthesized

3. G2 Phase – Shortest of the three phases. Organelles and molecules required for division are produced. When the cell completes this phase it is ready to enter the M phase and begin the process of cell division

Mitosis Involves the centrioles (cell organelles made of

proteins and microtubules) of the cell Occurs in four stages

1. prophase – chromosomes appear and nuclear envelope breaks down2. metaphase – chromosomes line up across center of cell 3. anaphase - sister chromatids separate into separate cells 4. telophase – chromosomes gather at opposite ends of two cells and two new nuclear envelopes begin to form

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

InterphaseDuring Interphase the chromosomes are not visible. The cell grows and replicates its DNA and centrioles

Prophase

Longest phase of mitosis Chromatin condenses and chromosomes

become visible The nuclear envelope begins to break down Centrioles separate and take positions on

opposite sides of the cell The spindle, a microtubule structure that helps

separate the chromosomes, begins to form

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Prophase

Metaphase

Chromosomes line up across the center of the cell.

Microtubules connect the centromere of each chromosome to the two poles of the spindle

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Metaphase

Anaphase

The centromeres that join the sister chromatids of the chromosome split and allow the sister chromatids to separate and become individual chromosomes

The chromatids continue to move until they have separated into two groups near the poles of the spindle

Anaphase ends when the chromatids stop moving

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Anaphase

Telophase

Final stage of mitosis Chromosomes begin to loosen and into a tangle

of dense material Two new nuclear envelopes begin to reform

around the two clusters of chromosomes The spindle begins to break apart and a

nucleolus becomes visible in each daughter nucleus

Mitosis is now complete, 2 nuclei are formed, but the cells are not yet separated

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Telophase

Cytokinesis

Separation of cytoplasm within a single cell Typically occurs at the same time as telophase Cell membrane is drawn inward until the

separation of the cytoplasm into two nearly equal parts

Each part contains its own nucleus and organelles

In plants, a cell plate forms midway between the divided nuclei and a cell wall begins to appear in the cell plate

Centrioles

Chromatin

Interphase

Nuclear envelope

Cytokinesis

Nuclear envelope reforming

Telophase

Anaphase

Individual chromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindle forming

Cytokinesis

Mitosis and Cytokinesis Video Segment

..\..\bio CD\Chapter 10A.mpg

Did you know????

All of the DNA in an adult human body could fit inside one ice cube, but if unwound, stretched out and joined end to end, it could reach from the earth to the sun and back again approximately 400 more times. 

Homework Assignment

This will be due tomorrow, start it in class now because it is a long assignment!!!

Suppose you were small enough to hitch a ride on a chromosome located in an animal cell that goes through mitosis and cytokinesis. Describe what you would see happening during EACH phase of the process