Cells, Chromosomes and DNA

Reproduction would not be possible without division of cells and the distribution of genetic material (DNA). All body cells are capable of division called mitosis

this is not used for reproduction but for growth and replacement of damaged cells

CELL CYCLE

represents the events during the life span of a cell consists of Interphase, Mitosis and Cytokinesis

Interphase: is a period of nondivision. It consists of: cell growth DNA synthesis (single stranded chromosomes become double stranded)

Mitosis : is a period of active division of both nuclear and cellular contents.

TERMINOLOGY

CHROMOSOMES are hereditary structures located in the nucleus that contain instructions needed for all cellular activities. CHROMATIN is fine threadlike material made from all the chromosomes in the nucleus. Chromosomes are in this form before and after mitosis.

GENES are distinct sets of instructions on each chromosome; each gene codes for one specific trait or instruction. DNA is the chemical that makes up each gene on each chromosome.

NUCLEIC ACIDS are the chemicals that makeup DNA. HAPLOID: a cell that contains half the normal number of chromosomes ex: a gamete (sperm or egg) DIPLOID: a cell containing the full complement of chromosomes

DIAGRAM OF A CHROMOSOME: In the Nucleus Chromatin

DIAGRAM OF A CHROMOSOME: In the Nucleus Chromatin Chromosomes

DIAGRAM OF A CHROMOSOME: Single stranded In the Nucleus Chromatin Centromere Chromosomes Chromatid

DIAGRAM OF A CHROMOSOME: Single stranded In the Nucleus Chromatin Centromere Chromosomes Double stranded chromosome

MITOSIS: through a series of steps, sister chromatids separate and the cell divides into two daughter cells, each containing the same number of chromosomes as the parent and an equal amount of cellular contents (organelles and cytoplasm)

There are 5 stages of mitosis:

1. PROPHASE: chromatin changes into chromosomes and the nuclear membrane dissolves centrioles organelles that provide attachment for spindle fibers, move to opposite poles of the cell. spindle fibers attach to each centromere

spindle fibers are small fibers that attach to the centromere of each chromosome; they contract and pull each chromatid to opposite poles in later phases.

Nuclear Membrane dissolving Centriole

2. METAPHASE: chromosomes line up along the equatorial plate (the center of the cell) by the tugging of spindle fibers that are attached to each centromere.

Chromosomes Spindle Fibers

3. ANAPHASE: centromeres divide and each sister chromatid is pulled to opposite poles the same number of chromatids will be found at each pole

separate at the centromere Sister Chromatids separate at the centromere

4. TELOPHASE: chromosomes dissolve at each pole, into chromatin a nuclear membrane forms around each chromatin mass.

Two Nuclei begin to form

5. CYTOKINESIS: cytoplasm and cell organelles separate cleavage furrow forms in animal cells to divide the parent cell into two new daughter cells. cell plate forms in plant cells

Two Identical Daughter Cells