Cell Growth and Division

Generally have more DNA than prokaryotes

Chromatin is chromosomes and histones

Contain multiple chromosomes

DNA and histone molecules form structures called nucleosomes

Chromosomes make it possible to split the DNA correctly in cell division

Lack nuclei

Contain a single, circular DNA chromsomes

Circle chromosome contains all or almost all genetic infromation

DNA molecules found in cytoplasm

Most of the contents of the cell are in the cytoplasm

Four phases involved

G1, S, G2, M phase

Time taken in each depends on each type of cell

Interphase is an in-between stage from one cell division to another                 G1, S, G2 are apart of interphase

Mitosis is the first step in the division of the cell's nucleus, second step is cytokinesis

3 main stages

Cell start to begin to start the process when they have grown to a certain size

Process of cell division in prokaryotes is known as Binary Fusion

1. DNA duplicates

2. Cell membrane indents

3. Cell divides with the product of 2 new cells

1st phase

Usually longest step

Chromosomes visible and spindle form

Spindle fibers extend from the centrioles

When done chromosomes coil and nucleus disappears

2nd Stage

Generally the shortest step

Chromosomes line up

Spindle fibers attach

Spindle fibers come from both sides of the cell

3rd stage

Begins with chromatids separate ad move away

Chromosomes separate into 2

Move with spindle fibers to sides of cell

Ends when chromosomes  are separated into 2 groups

Final stage of mitosis

Chromosomes unravel into tangle of chromatin

Nuclear envelope reappears

Spindle fibers break apart and nucleuolus becomes visible

NOT the final stage in cell division, only in mitosis!!!

Cytokinesis is final stage in cell division

Splits one cell into two

Cell membrane is pulled inward

Pinches in until cytoplasm is into nearly 2 parts

Each part contains a nucleus and organelles

Can't draw inward because it has a rigid cell wall

Cell plate forms forms halfway, dividing the nuclei

Final stage in cell division

Cell plate grows into cell membranes splitting the cell

Spilt cell into two

Caused by defects in genes that regulate growth and division

Sources- smoking, chewing, radiation exposure, genes defect, and viral infection

Control over cell broken down

Some cells don't respond to external growth regulators

Others don't respond to internal regulators

When cancer tumor is localized, removed by surgery

Some can be stopped if found early

Use targeted radiation for cancers that grow rapidly

Chemotherapy slows cells growth process down

Chemo has dangerous side effects because also affects healthy cells

One parent

Offspring is identical to parent

Enables populations to increase very rapidly

Definition- production of genetically identical offspring from one parent

Usually in single-celled organisms,but is found in many multi-celled too

Two parents

Offspring shares features from both parents

Is the fusion of two separate parent cells

Offspring inherit genetic information from both parents

Most animals an plants produce sexually

For many single-celled organisms asexual is a form of survival

Asexual only have to have one parent, makes reproducing faster and easier

Sexual reproduction provides more diversity

Some organisms produce asexually and sexually

Sexual, some offspring may have the right combination of genes to survive while others may not

Happens when cell is too big

DNA has too many things to do

Causes cell to divide

Critical information stored in DNA moleclue

As size of cell increases, DNA does not

Food, oxygen, and water enter through the cellular membrane

Waste products leave through cell membrane

Exchange of materials depends on surface area of cell

Rate of food and water being used up and waste produced depends on cell volume

Formula for area- length x width

Formula for volume- length x width x height

The process of a cell dividing into two daughter cells is called cell division

Daughter cells are what the two cells that divided are called

Before division a cell copies all of it's DNA

Results in an increase in the ratio of surface area to volume

Each daughter cell gets one complete copy of DNA

Blastocyst, a hollow ball of cells

At early stage blastocyst begin to specialize

Totipotent- able to develop into any cell

Outer cells form tissue, while cells become part of embryo mass

Inner cells are pluripotent- can't develop into ANY cell

Unspecialized cells

Embryonic cells are pluripotent, found in early embryo

Stem cells are multipotent- can develop into many types of different cells

Embryonic cells develops after fertilization

Different cells embryonic develop are neurons, fat cells, smooth muscle, and macrophage

Scientists are using stem cells to make organs

Offer the chance to inject stem cells into damaged area

Some want to use Embryonic cells to make more cells for other organs

Make whole organs

Could end up saving peoples' lives

Harvesting embryonic cells means to kill the embryo

People think it's wrong to kill a human

Some argue that the embryo is not yet alive

Subtopic

The use of stem cell is fine, doesn't hurt anything or one

Most people are confused between stem cells and embryonic cells