The Nucleus Asexual Reproduction Mitosis Cell Division General

The Nucleus Asexual Reproduction: Mitosis & Cell Division

General Info: Nucleus: –the “brain” of the cell –controls the cells activities –responsible for cell division, protein synthesis

General Info Cont. Nucleus: – contains genetic material called DNA – DNA long chain (chromatin) of genetic information (eukaryotes) – In prokaryotes (bacteria) DNA is in the shape of a ring called a plasmid

Nucleus Nucleolus Chromatin

Chromosomes: – made of Deoxyribonucleic Acid DNA wrapped around proteins – Chromosomes in eukaryotes are “rod shaped” structures made of DNA and proteins

Chromosomes: • consist of 2 halves called chromatids • “sister chromatids” are connected in the center by a centromere

Chromosome (Coiled chromatin)

Ck question Topic: DNA and Chromosomes Date: 1 -4 -2010 1. 2. 3. 4. Genetic material of a cell is called … The location of #1 The ring of DNA found in Bacteria is… Chromosomes consist of 2 halves known as…

Chromosome Numbers: • Each species has a characteristic number of chromosomes in each cell. • ex. Fruit flies (drosophila) = 8 chromosomes • horse has 64 chromosomes • humans have 46 and chimpanzees have 48 chromosomes

From 7 characteristics of living things: All living things Grow • Growth occurs from the division of cells. • Cell Division (cellular reproduction) allows cells to: 1. Grow in size 2. Grow in number 3. Replace worn out, injured or dying cells

2 Forms of Cellular Reproduction (cell division): 1. Asexual Reproduction involves only one parent cell a. Occurs in Autosomes or somatic cells … body cells b. Plants/animals

2 Forms of Cellular Reproduction (cell division) Cont… c. protists (protozoan) = single celled organisms (binary fission) d. fungi e. bacteria = binary fission

2 Forms of Cellular Reproduction (cell division): 2. Sexual Reproduction involves 2 parents cells a. Gametes = sex cells b. Making gametes!!!

Sexual reproduction: Occurs in sperm cells and egg cells

The Cell Cycle Asexual Reproduction aka MITOSIS The Cell Cycle is responsible for: – birth and death of a cell – Cell division of nucleus, home of hereditary information…chromosomes – Cell division (Cell Cycle) consists in 3 processes

Cell Cycle consists in 3 processes 1. Interphase 2. Division of the nucleus= mitosis 3. Division of the cytoplasm = cytokinesis

Ck question Topic: Cell reproduction Date: 1 -4 -2010 1. How many chromosomes does a normal humans have? 2. Identify 3 reasons cells divide. 3. The 2 types of cellular reproduction are… 4. Define gametes. 5. Define autosome.

Before a cell divides…. Interphase (nucleus) • Cell spends most time here

Interphase: • Divided into 3 phases 1. G 1 – cells grow to mature size 2. S – DNA is copied or duplicated called DNA replication 1. G 2 – cell prepares to divide • Some cells have a G 0 phase, they do not replicate after maturity. Ex. Nervous System

Mitosis: One cell (PARENT CELL) divides into 2 identical cells (Daughters) – – 1. 2. 3. 4. divisions: nucleus divides a series of chronological steps: prophase Division of the metaphase nucleus (DNA)!! anaphase telophase

Mitosis

Prophase: • Chromatin condenses, becomes visible strands of DNA called chromosomes • 2 chromosomes are made of “sister chromatids” • chromatids are connected by centromere • centrioles in animal cells begin to separate (opposite ends or poles)

Prophase Cont. • spindle fibers form (football shape) from the centrioles and connect to centromere of each chromatid • nuclear membrane fades • chromatids (chromosomes) begin moving to center

Spindle fibers Chromosomes Centrioles Centromere

Metaphase: (middle) • chromosomes (chromatids) line up in the middle of the cell • centromere divide • chromosomes are pulled apart separate chromosomes (? ? ? )

Spindle fibers Chromosome Centromere

Anaphase: (away) • centromere divides • chromatids separate • move to opposite ends of cell • complete set of chromatids go to each pole

chromatid

Telophase: • final step of mitosis • chromatids unwind, spindle fibers disappear • nuclear membrane forms around each of chromatids

Cytokinesis: • final step in the cell cycle • cytoplasm (and organelles) divide equally in cells • animals-pinching in of the cell membrane forming a cleavage furrow • plants - cell plate forms across the middle growing outward

In animal cells • (begins outside the cell)

In plate cells • (begins inside the cell)

Results of Mitosis: • division of the nucleus (Asex. Reprod. ) • products are 2 new cells with identical information to each other and to the parent cell • most cells reproduce asexually mitosis – ex. Of cells produced through mitosis include: in animals: blood cells, skin cells, cheek cells, in plants: root cells, stem cells, leaves

Parent Cell Identical Daughter Cells

Identical Daughter Cells Two identical daughter cells Parent Cell

• mitosis