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Cell Growth and Division
CHROMOSOME STRUCTURE
• (CHROMATIN) in Nucleus is coiled into
CHROMOSOMES.
• Chromosomes made of DNA and Proteins.
• The DNA wraps around Proteins called
HISTONES.
• Each half of the
Chromosome is called a
CHROMATID or
SISTER
CHROMATIDS.
• The Centromere holds
the Two Chromatids
together.
• The DNA of most Prokaryotes comprises
only ONE Chromosome.
• Circular DNA Molecule and associated
Proteins.
CHROMOSOME NUMBERS
• HUMAN CELL CONTAINS 46
CHROMOSOMES, OR TWO SETS.
• TWO COMPLETE SETS OF
CHROMOSOMES IS CALLED A
DIPLOID CELL. (abbreviated as 2n.)
• EVERY ORGANISM HAS A DIPLOID
NUMBER (2n).
• EXAMPLES: FRUIT FLIES - 8,
LETTUCE - 14, GOLDFISH 94, AND
HUMANS 46.
• ONLY ONE COMPLETE SET OF
CHROMOSOMES IS CALLED A
HAPLOID CELL. (abbreviated as 1n.)
• GAMETES, EGGS AND SPERM
CONTAIN ONLY ONE COMPLETE
SET.
• HUMAN SPERM OR EGG (GAMETE)
CONTAINS 23 CHROMOSOMES, (1n)
FOR ALL HUMANS.
• EGG AND A SPERM JOIN TO PRODUCE
A NEW INDIVIDUAL, CALLED
FERTILIZATION.
• THE SINGLE CELL THAT RESULTS IS A
ZYGOTE.
• IT CONTAINS TWO COMPLETE SETS
OF CHROMOSOMES, ONE SET FROM
EACH GAMETE, FORMING A DIPLOID
CELL.
• SEX CHROMOSOMES Determine the
SEX of an Organism.
• In Humans, Sex Chromosomes are either X
or Y. Females XX and Males XY
• All the Other Chromosomes are called
AUTOSOMES.
• TWO of the 46 Human Chromosomes are
Sex Chromosomes, the remaining 44 are
Autosomes.
• MATCH SET OF AUTOSOMES ARE
CALLED HOMOLOGOUS
PAIRS. BOTH CONTAIN
INFORMATION THAT CODES THE
SAME TRAIT (GENES).
Example Eye Color.
CELL DIVISION
• All cells are derived from preexisting cells.
• Cell division differs in prokaryotes and
eukaryotes.
CELL DIVISION IN PROKARYOTES
BINARY FISSION is the Division of a
Prokaryotic cell INTO TWO Offspring
Cells.
Binary Fission consist of THREE General Stages:
STAGE 1 - The Chromosome makes a COPY of
Itself, Resulting in Two Identical Chromosomes.
STAGE 2 - The Cell continues to grow until it
reaches approximately TWICE its Normal Size.
Then a CELL WALL Begins forms between the
Two Chromosomes.
STAGE 3 - The Cell SPLITS into TWO NEW
CELLS. Each New Cell contains on the Identical
Chromosomes.
THE CELL CYCLE
• THE CELL CYCLE CONSISTS OF
THREE PHASES:
A. INTERPHASE
B. MITOSIS
C. CYTOKINESIS
• MITOSIS is a Series of PHASES in Cell
Division during which the NUCLEUS of a
Cell Divides into TWO NUCLEI WITH
IDENTICAL GENETIC MATERIAL.
• MITOSIS OCCURS ONLY IN
EUKARYOTES.
INTERPHASE
• INTERPHASE IS THE PORTION OF THE
CELL CYCLE BETWEEN DIVISION.
• Interphase is the LONGEST Phase in the Cell
Cycle of a typical Cell. Interphase used to be
referred to as the "RESTING PHASE".
• During Interphase, cells carry on all their usual
functions, such as respiration and enzyme
production. The Cell also GROWS and
DEVELOPS into MATURE FUNCTIONING
Cells while in Interphase. It is the period of
normal metabolic activity.
• INTERPHASE CONSIST OF THREE
PHASES:
• G1 PHASE - PERIOD OF NORMAL
METABOLIC CELLULAR ACTIVITIES:
THE NUMBER OF ORGANELLES AND
AMOUNT OF CYTOPLASM IN A CELL
INCREASE.
• S PHASE - THE GENETIC MATERIAL
(DNA) IS DUPLICATED (COPIED). THE
CHROMOSOMES OF THE CELL
REPLICATE
• G2 PHASE - Structure directly involved
with mitosis are formed. The Cell makes
the Organelles and substances it needs for
Cell Division. A time during which the Cell
prepares to divide.
• REPLICATION IS THE PROCESS OF
COPYING GENETIC MATERIAL.
• REPLICATION RESULTS IN TWO
IDENTICAL COPIES OF A
CHROMOSOME CALLED SISTER
CHROMATIDS.
CELL DIVISION
• CELL DIVISION IS THE PROCESS BY
WHICH ONE CELL PRODUCES TWO
NEW IDENTICAL DAUGHTER CELLS.
• MITOSIS - FIRST STEP. A SERIES
OF PHASES IN CELL DIVISION
DURING WHICH THE NUCLEUS OF A
CELL DIVIDES INTO TWO NUCLEI
WITH IDENTICAL GENETIC
MATERIAL.
• CYTOKINESIS - SECOND STEP. THE
CYTOPLASM OF THE CELL DIVIDES
INTO TWO NEW CELLS CALLED
DAUGHTER CELLS.