Download BIOLOGY CLASS NOTES UNIT 6 Cell Growth and Division

Unit 6: Cell Growth and
Division
Mrs. Howland
Biology 10
Rev. Jan 2016
Living Things GROW
How does growth occur in living things?
By cells increasing their size?
By number of cells increasing?
WHY?
What happens when cells INCREASE in size?
Larger Cells are Inefficient
Cells function using a set amount of DNA and
transport of materials across the membrane
Cells that are
too large have
less surface area
for transport ~
They cannot
keep up with
their demand!
Many, smaller cells
allow for greater
efficiency!
Cells DIVIDE
Cells DIVIDE into 2 “daughter” cells by way of
CELL DIVISION
BEFORE cell division, DNA is replicated
Each daughter cell gets a complete copy of DNA
TWO TYPES of cell division
Asexual reproduction
Sexual reproduction
ASEXUAL REPRODUCTION
Some living things such as bacteria (single cell organisms) do not
reproduce the way animals do—they must divide in order to
reproduce!
Asexual reproduction is when one cell divides
to create two cells that are identical to the
original
Occurs quickly
Efficient
Bacteria (single celled organisms)
Multicellular organisms such as hydra
ASEXUAL REPRODUCTION
HYDRA
SEXUAL REPRODUCTION
Another way to form new cells is by the fusion
of two separate ‘parent’ cells (what does fusion mean?)
Sexual reproduction is when offspring (new
cells) are produced from two separate parent
cells
Parent cells are special reproductive cells
Offspring inherit some DNA from each parent
Occurs for most plants and animals, some singlecelled organisms
What we know…location of DNA
VOCAB: Chrom-WHAT???
Chromosome ~ organized package of DNA, located in
cell’s nucleus
Chromatin ~ fiber within a chromosome, consists of
protein and DNA, major proteins are histones
DNA coils around the histone proteins to form beadlike
structures
VOCAB: Chrom-WHAT???
Chromatid ~ one of TWO (2) identical halves of
a replicated chromosome (during cell division)
Why CHROMOSOMES?
DNA is specially packaged into CHROMOSOMES
Allows for easy and correct separation during
cell division
Which makes more sense?
OR
CELL CYCLE ~ How a cell divides
CELL CYCLE:
Grow
Prepare for division
Divide, forming TWO (2) daughter cells
REPEAT: Daughter cells enter their own, new cell
cycles!
PROKARYOTIC Cell Cycle
Bacterial cell (binary fission)
EUKARYOTIC CELL CYCLE
FOUR PHASES
MITOSIS = division of cell nucleus
PMAT
Prophase
Chromatin condenses
into chromosomes.
Spindle begins to
form. Nuclear
envelope breaks
down.
Metaphase
Chromosomes line up
along equator (center)
of cell. Chromosomes
are connected to
spindle fibers.
Anaphase
Chromosomes break
into separate sister
chromatids (think
“chromosome kids”)
and begin to move
apart.
https://www.youtube.com/watch?v=C6hn3sA0ip0
Telophase
Chromosomes gather
at two opposite ends
of the cell. Formation
of two new nuclear
envelopes.
VOCAB: Centrioles and spindle
Centrioles are located in ANIMAL CELLS
Structures that will separate and form spindles
during cell division
Are duplicated during INTERPHASE
BEFORE and AFTER Mitosis
BEFORE mitosis occurs, the cell is in INTERPHASE
Cell grows
DNA replication
AFTER mitosis, final step is CYTOKINESIS
CYTOKINESIS is when the cytoplasm pinches along
the center, forming two new daughter cells
Daughter cells have identical set of duplicate
chromosomes
CYTOKINESIS
Cytokinesis in ANIMAL vs. PLANT cells
Mitosis under MICROSCOPY
Mitosis under MICROSCOPY
MEIOSIS = produces 4 geneticallyunique cells
An organism inherits a SINGLE COPY of every
gene from each parent
HOMOLOGOUS CHROMOSOMES ~ pairs of
chromosomes that have 1 chromosome from
father and 1 from mother
DIPLOID ~ Cell has both sets of homologous
chromosomes (2 complete sets of genes, called
‘2N’)
HAPLOID ~ Cell has single set of chromosomes
(1 set of genes, called ‘N’)
MEIOSIS I
PROPHASE 1:
• Cell begins to divide.
• Chromosomes pair up.
• EACH CHROMOSOME PAIRS WITH
ITS CORRESPONDING
HOMOLOGOUS CHROMOSOME
• CROSSING OVER ~ produces new
combinations of alleles
MEIOSIS I
METAPHASE 1:
• Paired homologous chromosomes
line up along center of cell
ANAPHASE 1:
• Spindle fibers pull homologous
chromosome pairs to ends of celll
MEIOSIS I
TELOPHASE I and CYTOKINESIS
• Nuclear membrane forms
around chromosomes
• 2 new cells are formed
• UNIQUE set of genetic info
Meiosis II
PROPHASE II:
Chromosomes become
visible but DO NOT pair
METAPHASE II:
Chromosomes line up
in center of cell
ANAPHASE II: Paired
chromosomes separate
TELOPHASE II and CYTOKINESIS:
Formation of 4 daughter cells.
Genetically unique from one another.
Daughter cells contain only 2
chromosomes each, and are HAPLOID
(‘N’)
Mitosis vs. Meiosis
Mitosis vs. Meiosis
Meiosis = Sexual reproduction
TWO (2) STAGES OF MEIOSIS:
Meiosis I
Meiosis II
https://www.youtube.com/watch?v=nMEyeKQC
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