UNIT 7: Cell Division

BIG IDEA: Cell division is the process in the body to create

more cells and gametes

MITOSIS

Asexual Reproduction

Reproduction with only one parent

offspring are identical to parents

Sexual Reproduction

Requires 2 parentsNew individual is produced by

the union of the nuclei of two specialized cells (sperm & egg)

Chromosome Structure

Inside your nucleus are 3 billion nucleotides of DNA

In order to fit it is coiled and packed into a complicated but organized structure

Chromosome Structure

Histones-Proteins that DNA are wrapped around

Chromosome Structure

Chromatin-Less tightly coiled DNA wrapped around a histone

Chromatid

Chromosome

Chromosomes

Rod shaped structures made up of DNA and histones

Two identical halves are called chromatids Point holding together the chromatids is

called a centromere

Chromosomes

Structure in cells that undergo division and that contain hereditary information of the organism

In mitosis the chromosomes that undergo cellular division are called autosomes

Chromosomes

Draw a chromosome and label the centromere and the chromatids centromere

chromatid

How many chromosomes are present in an autosomal cell?

23 pairs or 46 chromosomes

Refers to DIPLOID: meaning that a cell possesses 2 complete sets of chromosomes

Why are there two sets of chromosomes?

– 1 set is from your mother and 1 set is from your father

– This leads to genetic variation because genetic information on chromosomes from your parents can be different Example: both chromosomes can code for eye color

except one can be for blue eyes and one for green eyes

Blonde Hair Black Hair

Genetic Variation

Why is genetic variation beneficial?

Causes a diverse collection of genes

Increase in survival

CELL CYCLE

Cycle that a cell goes through in order to make new cells

If an organism is unicelluar, than a new organism is created via the cell cycle

Cell Cycle Consists of Two Parts:

Mitosis:– Division of the

nucleus to form two identical nuclei

– REMEMBER: Hereditary material is found in the nucleus

Cytokinesis–Division of the

cytoplasm of the cell after mitosis

INTERPHASE

Interphase

Stage when a cell is between mitotic cycles:

A. G1- cell grows

B. S- DNA replication

C. G2- Organelle replication

MITOSIS

Prophase

Chromosome become visible

Centrioles move to opposite poles of the cells

Microtubules form spindles

Spindle fibers become attached to centromeres

Nuclear membrane disappears

Nucleolus disappears

Prophase:

Metaphase

Chromosomes attach to the microtubule spindles

Chromosomes line up on the equator of the cell

Anaphase

Centromeres double

Chromosomes(sister chromatids) move to opposite poles

Division (cleavage furrow) appears

Telophase

Begins when chromosomes reach the poles

Chromosome uncoil and become invisible

Spindle disappearsNuclear membrane formsNucleioli reappears

Telophase

Cytokinesis in Animal Cells

Begins during late anaphase

Cytoplasm is pinched off by cell membrane

Mitosis & Cytokinesis in Plant Cells

Main events are the same Plants do not have centrioles or

asters Cytokinesis cannot occur by

pinching off of membrane a cell plate forms between the new cells during anaphase or telophase

Cytokinesis

End with two identical daughter cells

Cells that divide rapidly

Plants Animals

Cells that seldom or never divide

Xylem (part of a plant)

Nerve Cells Muscle Cells