Bio Ch. 11-12: Cellular Growth and Division

cell division

process by which a cell divides

2 reasons that cells divide when necessary are

1. larger the cell becomes, more pressure on the DNA to produce more proteins

2. cell has more trouble moving nutrients across membrane

2 reasons cells divide for maintenance

1. for growth and repair in multicellular organisms

2. for reproduction in unicellular organisms

parent cell

cell that divided

Daughter cells

two cells that result from the division that carry the traits of the parent cell

Chromosome

DNA and proteins called histones; usually not seen except during cell division

Gene

unit of heredity

Genetic code

code that determines that inherited traits of an organism

Chromatids

replicated, identical copies of DNA attached at a centromere

Chromosome number

every species has a characteristic number of chromosomes

Humans have __ chromosomes

46

Homologous chromosomes

in sexually reproducing organisms, chromosomes occur in pairs

genes are the _____ on homologous pairs

same

chromosomes are the ____ size and shape

same

diploid cells

cell that contains both chromosomes of a homologous pair

2N

diploid cell

humans have 2N= __

46

Haploid cells

a cell that contains only one chromosome of each homologous pair

1N

refers to a haploid cell

Life cycle of a cell

cell grows, prepares for division, divides to form two daughter cells which begins the cycle again

Interphase

period between cell division

G1 (Gap)

growing, synthesize proteins and organelles

S (Synthesis)

DNA replicated; attached at centromere

G2 (Gap)

organelles and molecules required for cell division are produced

Mitosis

division of nuclear material in which each new cell obtains the same number of chromosomes and genetic code as the original cell

There are ____ stages of cell division

four

prophase

chromosomes become visible and condense, nuclear membrane breaks down, centrioles move to opposite sides of the cell, and spindle fibers form

plant cells do not have

centrioles

Metaphase

alignment of chromosomes at the center of the cell; microtubules attach to the centromeres

Anaphase

chromatids divide at the centromere and move along spindle fibers to opposite poles

Telophase

chromosomes disperse (no longer distinct); nuclear membrane reforms

cytokinesis

cytoplasm pinches inward and cell membrane surrounds each part

cell plate forms in

plant cells

mitosis results in

two daughter cells with the same chromosome number and genetic code as the parent

reproduction in unicellular organisms

mitosis (asexual reproduction)

Multicellular organisms gain _______ cells through mitosis

somatic

cell division (regulating the cell cycle)

experiments show that when cells come into contact with other cells, they don’t grow

cell cycle regulators

discovered by Hunt and Kirschner

Cyclin

protein that regulates the cell cycle

Cyclins have now been discovered to be ___ ____ _____ __ ______

an entire family of proteins

When cancer occurs

the body loses the ability to control growth or respond to external or internal regulators

Development of cancer depends on:

a. genetic predisposition

b. time of exposure to carcinogens

c. amount of carcinogens exposed to