Bio1151b
Chapter
12
The Cell Cycle
The continuity of life is based upon
cell
, the
reproduction
of cells. Cell
division
takes place in a sequence of events called the cell
.
Cell
division
is asexual and results in
identical
cells; each of which receives an exact copy of the genetic material,
, from its "parent".
Prokaryotes reproduce by a type of cell division called
fission,
where the DNA is
, and then the two daughter DNA strands actively move apart.
Eukaryotic DNA is packaged
into
, a complex of
and
that
condenses
into
during cell
division.
cells have
sets of chromosomes and reproduce asexually by
, while
(sex cells) have
set of
chromosomes
and reproduce by
.
The cell
cycle
consists of an
and a
phase.
Interphase can be divided into
subphases
,
, and
.
The mitotic phase consists of
, the division of the nucleus, and
, the division of the cytoplasm.
Mitosis
consists of 5
phases,
or stages: 1)
, 2)
, 3)
, 4)
, 5)
.
In
, chromatin condense into visible
, and the
mitotic
arises
from
the
and is made of
.
In
, the nuclear envelope breaks down, and
microtubules attach to the
of chromosomes.
In
, the
microtubules move the chromosomes to the
, or equatorial, plate.
In
, sister
separate, and move along the
kinetochore
toward opposite ends of the cell.
In
, genetically identical daughter
form at opposite ends of the cell.
Cytokinesis:
In animal cells, a
furrow
forms, and a
ring of
splits the
cell.
In
plant
cells,
a cell
, fused from
, grows at the
equator,
then new cell
form between the daughter cells.
Review:
Mitosis and Cytokinesis Animation
Bio1151b
Chapter
13
Meiosis and Sexual Life Cycles
All living organisms can
reproduce,
and transmit
from one generation to the next, with variation.
The units of heredity are
segments
of
called
. Each gene is found at a region on a
called its
. An organism's total
genes
is its
.
In
reproduction, one parent produces
genetically
offspring
by
or
fission.
In
reproduction, two parents produce offspring that have unique combinations of
inherited from each
parent.
A
is an ordered, visual
representation
of the
in a cell.
In humans, each
cell has
chromosomes made up of two sets, with one set coming from each parent.
44 of these are pairs of
chromosomes, or
, and have the same
; each of the pair comes from each of the parents of the individual.
The other two chromosomes are
chromosomes, called X and Y, which determine the
gender
of the individual. Cells having a full
complement
of chromosomes are
.
Each
chromosome
consists of two identical sister
, attached to the
.
are the sex
cells
involved in
reproduction, and are
, containing only one set of chromosomes.
Gametes are produced from
cells in organs called
by
meiosis.
occurs when a sperm fuses with an ovum, forming a diploid
, which grows and develops into an adult
organism.
Since
meiosis
reduces the number of chromosome sets from
to
, two cellular divisions are required.
Meiosis
is the chromosome
division, and
meiosis
produces
haploid daughter cells.
Prophase
I
Metaphase
I
Anaphase
I
Telephase
I
Meiosis
II
Sexual reproduction produces genetic
by several mechanisms:
independent
,
crossing
, and
random
fertilization.
The tremendous genetic variation made possible by
meiosis
and
reproduction provides raw material for evolution by
selection.