Cell Growth and Division

Cell Division is the Cell’s way of Reproducing itself

Reproduction

IS A LIFE PROCESS MORE OF THE SAME UNIT IS FORMED NOT ESSENTIAL FOR SURVIVAL IS A NEED TO PERPETUATE SPECIES

CHAPTER OBJECTIVES

At the end of lecture discussion, the learners are expected to:

Explain Cell Reproduction at

the molecular level, with

emphasis of the role of DNA

and Chromosomes

Describe the limits to cell growth.

Identify the types of cells in the body

of an organism.

Name and describe the sequence of

stages in Mitosis and Meiosis.

Describe the chromosamal changes

in Mitosis and Meiosis.

Give the significance of cell division.

Trace the formation of sperm and egg cells through the process of spermatogenesis and oogenesis.

Cell Growth & Reproduction

Review of Terms

DNA

Chromatids

Histones

Helix

Chromosome

Chromatin

Nucleosomes

DNA Replication

DNA possesses a

remarkable ability

to create copies of

its own structure

DNA Replication cont’

REPLICATION

Occurs as the

double strand of

DNA unzips at

certain points

(synthesis stage)

Limits of Cell Growth

Cells of human adult are no larger than human babies. Cells eat and defecate Cells know to adapt Cells growth and division rate vary.

Sometimes cell growth and division become

uncontrollable (cancer cells)

CELLS OF THE HUMAN BODY

Somatic CellsDiploid number (2N) or complete set of (46) Chromosomes

Ex.Skin CellsLung Cellsetc.

Reproductive CellsHaploid number (N) or half (23) number of chromosomes.

Ex.Sperm CellEgg Cell

Assessment Break

Explain the limits of Cell Growth.

Why do cells divide?

Distinguish between

Somatic and Germ Cells

Haploid and Diploid

MITOSIS

Mitosis is the

first step in

growth and

differentiation

of somatic

cells.

During Mitosis Chromosomes duplicate and daughter cells receives the

same amount of chromosomal

material as the parent cell.

MITOSIS cont’

Interphase

G1 ~ Presynthetic

S ~ Synthetic Phase

G2 ~ Postsynthetic stage

Interphase

( not a phase of Mitosis)

Growth occurs as organelles double (G1)Chromosomes (DNA) duplicates (S)Growth occurs as cell prepares to divide (G2)

The Major Events of Cell Division

KARYOKINESIS

SPLITTING OF THE NUCLEUSINSIDE NUCLEAR EVENTS OF THE CELL

CYTOKINESIS

CYTOPLASMIC DIVISIONOUTSIDE NUCLEAR EVENTS OF THE CELL

Mitosis

Phases of Mitosis Mitosis begins after Interphase

Stages/Phases

Prophase

Metaphase

Anaphase

Telophase

ProphaseEarly ProphaseCentrioles move to the poles of the cellChromosomes appear as long, this threadsNucleus becomes less distinct

Nuclear membrane is still visibleAsters are formed

ProphaseMiddle Prophase

Centrioles begin to organize spindle fibersSister chromatids are formed with the centromere as point of attachment

ProphaseLate ProphaseCentrioles are

nearly at the opposite sides of the nucleus

Nuclear membrane slowly desintegrates

Nucleulus is no longer visible

Chromosome move toward the equator

Spindle fibers attach to the centromere of each chromosome

Metaphase Nuclear membrane has completely disappearedThe centromere of each double-stranded chromosome is attached to a spindle fiber at the equator

Centrioles are at the opposite ends of the polesChromosomes line up at the center forming metaphase plate

Anaphase

Early AnaphaseSister

chromatids separate and begin moving toward opposite poles of the cell

Sister chromatids start to move toward the poles, seemingly being pulled by the thread or fibers

Anaphase

Late AnaphaseTwo sets of new,

single stranded chromosomes start to migrate near their respective poles

Cytokinesis begins

A slight cleavage furrow in the cell membrane begins to form in the region of the equator

Telophase

New nuclear membrane starts to form in each new cellChromosomes become longer, thinner and less distinctThe nucleus reappears

Centrioles are replicatedCytokineseis is nearly completeSpindle fibers and asters disappearThe cleavage furrow deepens and the cell finally divide onto two parts

2nd Interphase: 2 cell stage

o Nuclear membrane are complete in each cells

o Chromosomes are no longer visible

o Cytokinesis is complete

o Two new daughter cells are formed, each with a complete set of materials as the parent cell

The process of Mitosis

Occur in less than an hour or longer ( some in just 23 minutes)

Brain cells do not dived when mature

Most frequent/fast in human embryo formation

Assessment Break

Define Mitosis. Why is it important?

What are the stages of mitosis?

What body cells are involved in mitotic process?

When is the process of mitosis faster? Slower?

Meiosis

A cell division forming reproductive cells

OogenesisSpermatogenesis

Occurs in two cycles of division

Meiosis Dissected: Stages

Meiosis involves two

consecutive divisions

It involves “Crossing

Over” or the exchange of DNA traits

1st & 2nd Meiotic Division

Parent Sex Cells

Chromosomes duplicate

Crossing over

1st Cell division(2 daughter

cells)

2 daughter cells

Chromosomes pair up

Chromosomes separate

2nd Cell Division) Cell divides into 4 sex cells with haploid

chromosomes

Mitosis VS Meiosis

Gametogenesis

Meiosis only happens when your body is ready to produce

reproductive cells

Spermatgenesis ~ formation of sperm cells

Oogenesis ~ formation of egg cells

Spermatogenesis

The formation of

male gametes

An example of Meiosis

Oogenesis

Formation of Female Gamete

An example of Meiosis

SPERMATOGENESIS VS OOGENESIS

Assessment Break

Define meiosis. How is it different from mitosis?How many cells are formed after the first cell division in meiosis? After the second division?What is gametogenesis?Compare and contrast spermatogenesis and oogenesis.