Cell Cycle and Mitosis

Cell Cycle and MitosisCell Division — process by which a cell divides into 2 new cells

Parent Cell

2 Daughter Cells

Parent Cell

2 Daughter Cells

•The original cell is called the parent cell; 2 new cells are called daughter cells

Why do cells need to divide?

● Living things grow by producing more cells, NOT because each cell increases in size

● Repair of damaged tissue

● If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell

Do you remember?1) Which cell organelle controls all cell

functions?

2) What does this cell organelle contain?

3) What do ALL cells need in order to have the directions/code to perform functions correctly?

Nucleus

Genetic Information

DNA

DNA•DNA is located in the nucleus and controls all cell activities including cell division•Long and thread-like DNA in a non-dividing cell is called chromatin•Doubled, coiled, short DNA in a dividing cell is called chromosome

Consists of 2 parts: chromatid and centromere

Compare and Illustrate DNADNA in NON-DIVIDING Cell DNA in a DIVIDING Cell

Chromatin

Duplicates itself

Coils up into chromosomes

•Chromatin to chromosomes illustration:

Why does DNA need to change from chromatin to chromosome? More efficient division

o2 identical “sister” chromatids attached at an area in the middle called a centromere

oWhen cells divide, “sister” chromatids separate and 1 goes to each new cell

•Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell•Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell

Cell Cycle and Mitosis

•Every organism has its own specific number of chromosomes Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs

•All somatic (body) cells in an organism have the same kind and number of chromosomes. Examples: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes

Fruit fly = 8 chromosomesFruit fly skin cell = 8 chromosomesFruit fly heart cell = 8 chromosomesFruit fly muscle cell = 8 chromosomes

Cell Cycle -- series of events cells go through as they grow and divide•Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again

Cell Cycle Outline● Interphase

G1: Cell Grows S: DNA Replicates G2: Growth &

prepares for division

• Mitosis Prophase Metaphase Anaphase Telophase

• Cytokinesis

Cell Cycle and Mitosis

● Interphase● Prophase● Metaphase● Anaphase● Telophase● Cytokinesis

Get a friend and create a sentence to help you

remember the order of the cell cycle and mitosis. Use

the first letter of each term.

Interphase

● Interesting things happen!

1. Cell preparing to divide

2. Genetic material doubles

3. Cells most of their time in Interphase

•Mitosis – division of the nucleus into 2 nuclei, each with the same number of chromosomes•Mitosis occurs in all the somatic (body) cells

Mitosis BeginsProphase, Metaphase, Anaphase, Telephase

Prophase● Chromosome pair

up!

● Chromosomes become visible

● Nuclear membrane disappears

● Spindle fibers form

Prophase

Metaphase

● Chromosomes meet in the middle!

● Spindle Fibers connect to chromosomes

Metaphase

Anaphase

● Chromosomes get pulled apart

● Spindle fibers pull chromosomes to opposite sides

Anaphase

Telophase● Now there are

two!● Chromosomes

uncoil● Spindle fibers

disappear● Two nuclei are

formed

Telophase

Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides

In animal cells the cytoplasmpinches in

In plant cells a cell plate forms

•After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities

Cytokinesis

Mitosis is a type of asexual reproduction.

● There are two types of reproduction:

Asexual Reproduction

Sexual Reproduction

• parent reproduces by itself

• offspring is genetically identical to “mamma”

•Offspring is genetically unique

• creates diversity within population

1) Mitosis 2) Binary Fission3) Budding4) Spores5) Regeneration6) Vegetative Propagation

Asexual Reproduction

produce 2 identical daughter cells with the same # of chromosomes as the parent cell. (identical)

1) Mitosis 2) Binary Fission

• a parent cell splits into 2 daughter cells of = size

• w/ prokaryotes

3) Budding

4) Spores

• a new, duplicate organism forms at the side of the parent and enlarges until an individual is created.

• spores are surrounded by a tough coat to help them survive harsh conditions. .. Produced and released

5) Regeneratio

n

6) Vegetative Propagatio

n

• growth of new tissues/organs to replace those injured or lost.

• Common in invertebrates, especially Asteroidea (Sea Stars) and Annelida (Worms).

* In some multicellular plants * new plants develop from the

roots, stems, or leaves of the parent.

stolons

Sexual Reproduction

1) Meiosis

Cell division that results in haploid gametes; used for sexual reproduction

Haploid?

● When a gamete (sperm or egg) of an organism has HALF of the full amount of chromosomes

● Hap Half● Remember, human

cells have 46 chromosomes? Then the haploid # is 23

Sperm

Egg

Meiosis

Meiosis I● All chromosomes make

copes of themselves● This doubles the # of

chromosomes in the cell

Meiosis II● Begins in same two cells

created by Meiosis I● Creates FOUR new haploid

cells● Occurs in a manner very

similar to mitosis

● Occurs in the same four phases as mitosis but in two steps: Meiosis I and Meiosis II

Outline of Meiosis● Meiosis I

– Prophase I– Metaphase I– Anaphase I– Telophase I

● Meiosis II– Prophase II– Metaphase II– Anaphase II– Telophase II

Prophase I● Homologous

chromosomes from each parent pair up!

● They form two attached sets of chromatids called a tetrad

● There are MANY ways the chromatids can line up: this is one source of genetic variation.

Homologous chromosomes:

•1 from each parent

•carry genes that control the

sameinherited traits.

Metaphase I● Each tetrad meets

in the middle!● Spindle fibers

connect centromeres

● Crossing over of chromosomes may occur to provide additional genetic variation – 2nd source of genetic variation

Anaphase I

● Tetrads get pulled apart

• Homologous chromosomes move to opposite ends

Telophase I● Cells may finish

cytokinesis OR proceed immediately with Meiosis II

Prophase II● Chromosomes did

NOT replicate

● At this point, the cell is haploid because it no longer has one of every kind of chromosome that was in the original cell

Metaphase II● Sister chromatids

line up on individual spindle fibers

Anaphase II

● Sister chromatids are separated into each new cell

● Each new cell now has only HALF as many chromosomes as the parent cell in Prophase I

Telophase II● Each of the four

new cells completes reforming nuclei and cytokinesis separates the four new hapliod cells

How does meiosis lead to genetic variation?

● Look back at Prophase I & Metaphase I, what may lead to genetic variation?– There are MANY ways the chromatids can

line up

– Crossing over of chromosomes may occur

● What is another factor that could lead to genetic variation?– Random combinations of sperm and eggs

Interphase

Prophase 1

Metaphase 1

Anaphase 1

Telophase 1

Mei

osis

1In

terp

hase

Revie

w!

Mei

osis

2C

ytok

ines

is

Prophase 2

Metaphase 2

Anaphase 2

Cytokinesis

Note..Note..Male gametes

Female gametes

4 haploid gametes … 4 sperm by way of spermatogenesis

4 haploid gametes … 1 Ovum (egg) & 3 Polar Bodies by way of oogenesis

Sometimes cell division doesn’t go as planned…

Cell Division Regulation

● Internal and external factors regulate cell division.

● Cancer is the uncontrolled growth and division of cells.

● Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Cancer ● Benign – cancer cells

typically remain clustered together

● Malignant – cancer cells can break away or metastasize

cancer cellbloodstreamnormal cell

Benign Malignant

metastasize

Causes of Cancer

● Internal Factors

– Inheritance

– Mutations

● External Factors

– Carcinogens are substances that are known to produce and promote the development of cancer.

– Radiation– Chemical– Viruses

Skin Cancer

Nondisjunction Mutations● Improper separation of sister chromatids may

result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (monosomy)

Karyotype – a picture of an individual’s chromosomes so that the types of mutations might be seen

Trisomy 21 – Down Syndrome

Trisomy 18 - Edward's Syndrome

Meiosis Square Dance