cell division 1.ppt

8/12/2019 CELL DIVISION 1.ppt

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CELL DIVISION 1

MITOSIS

Hasimah Azit


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CELL DIVISION

FUNCTIONS IN:

Reproduction, Growth,

and Repair


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Core Concepts

All Organisms Consist of Cells and

Arise from Preexisting Cells

Mitosis is the process by which new cells aregenerated.

Meiosis is the process by which gametes are

generated for reproduction.

Unregulated Cell Division Can Lead toCancer


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Basic definitions

gene- basic unit of heredity; codes for aspecific trait

somatic cell- all body cells exceptreproductive cells

gamete- reproductive cells (i.e. sperm &eggs)

chromosome- elongate cellular structurecomposed of DNA and protein - they are thevehicles which carry DNA in cells


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diploid (2n)- cellular condition where each

chromosome type is represented by twohomologous chromosomes haploid (n)-

cellular condition where each chromosome

type is represented by only one chromosome

chromatid- one of two duplicated

chromosomes connected at the centromere

centromere- region of chromosome where

microtubules attach during mitosis andmeiosis


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Cell division involves

the distribution of identical geneticmaterial, DNA

to two daughters cells.

2n=46

2n=46

2n=46

two

identicaldaughter

cells


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Mitosis

The form of cell divisionby which a

somatic cell duplicates.

Mitosisis asexual reproduction.

Cell division is the continuation of lifebased on the reproduction of cells.
http://www.life.umd.edu/CBMG/faculty/wolniak/wolniakmitosis.htmlhttp://www.life.umd.edu/CBMG/faculty/wolniak/wolniakmitosis.html


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The Cell Cycle


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Interphase

1. G1(gap) phase:

a. protein synthesis and metabolic activities.

b. most cell are arrested in this phase.

2. S phase:

a. DNA replication takes place.

3. G2(gap) phase:

a. Cellular growth and preparation for M phase.


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Cell Cycle

The dividingand non-dividingstages in the

life of a cell.

Phases:1. Interphase: growth and DNA replication

2. Prophase

3. Metaphase4. Anaphase

5. Telophase

Mitotic division


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Interphase

Comprises about 90%of the cell cycle.

Cellular growth:

a. protein synthesis

b. metabolic activities

c. DNAsynthesis

Made up of three phases:1. G1phase

2. S phase

3. G2

phase


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mitosis- nuclear/chemical events resulting

in two daughter nuclei which

have identical genetic material toeach other and to the mother cell

cytokinesis- division of the cytoplasm.


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Interphase

Nucleusand nucleolusvisible.

Nuclearmembrane

nucleolus

cell membrane

chromatin


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Question:

What is a chromosome?


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Answer:

A chromosomeis made up of a DNA-

histone protein complex called chromatin.

Chromatinis a long, thin fiber that is folded

and coiled to form chromosomes.

DNAdouble helix

Histone

proteins

chromosome


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Chromosomes


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Question:

What is a replicated chromosome?


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Answer:

A replicated chromosomeconsist of two

strands of identical chromosomal material

called chromatids(sister chromatids).

chromatid

chromatid

S phase: chromosomes replicate

chromosome

chromosome

centromere


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Question:

When is a chromatida chromatid?


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Answer:

A chromatidis a chromatidas long as it is

held in association with a sisterchromatidat

the centromere.

chromatid

chromatid

centromere

chromosome


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Mitotic Phase

Mitosis (karyokinesis)

a. nucleardivision of genetic material.

b. prophase-metaphase-anaphase-telophase

Cytokinesis

a. cytoplasmic division.

b. Indicator of telophase.


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Prophase

Centriolesmove apart (not found in plants).

Spindle fibers form and attach from

centriolesto centromeres by kinetochores.

Nuclear envelope fragments and disappears.


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Prophase

late prophaseearly prophase

centrioles

spindle fibers

centromere

nuclear envelope

disappearing

aster

fibers


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Question:

What attaches the spindle fibersto

the centromeres?


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Answer: Kinetochores

sister

chromatid

sister

chromatid

centromere

spindle fiber kinetochores

centriole

aster

fibers


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Metaphase

metaphase plate

centrioles

spindle fibers

aster

fibers


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Anaphase

Centromeresuncouple and spindle fibers

shorten.

Sister chromatids separate and move apart.

After separation, chromatidsare now

considered chromosomes.


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Anaphase

During this phase, the cell contains twice

the normal number of chromosomes.

Cell begins to elongate.

At the end, there are equal numbers of

chromosomesat the poles.


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Anaphase

No longer sister chromatids, now chromosomes

centriolesspindle fibers

aster

fibers


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Telophase

Cleavage furrowdevelops in animal cells

(Cytokinesisbegins).

Cell plate develops in plants(no cleavage

furrows in plants).

Nucleolus reappears.cell plate
http://old.jccc.net/~pdecell/celldivision/oniontip.htmlhttp://old.jccc.net/~pdecell/celldivision/oniontip.html


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Telophase

Nuclear membrane reappears.

Chromosomesuncoil.

In the end, two genetically identical nuclei

(karyokinesiscompleted) are present.


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Telophase

cleavage furrow (cytokinesis)

nuclear membrane reformingnucleolus reappears


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Cytokinesis

Cytoplasmic division

Cell plate complete in plants

In the end, two separate daughter cells

produced with single nucleus.

cell plate


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Question:

A cell containing 20chromosomesat the

beginning of mitosis would, at its completion,

produce cells containing how manychromosomes each?


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Answer:

20 chromosomes


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Question:

A cell containing 40chromatidsat the

beginning of mitosis would, at its completion,

produce cells containing how manychromosomes each?


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Answer:

20 chromosomes

cell division 1.ppt

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