Chapter 8 Objectives Section 1 Chromosomes
Describe the structure of a chromosome. Identify the differences in
structure between prokaryotic chromosomes and eukaryotic
chromosomes. Compare the numbers of chromosomes in different
species. Explain the differences between sex chromosomes and
autosomes. Distinguish between diploid and haploid cells. Chapter 8
Chromosome Structure
Section 1 Chromosomes Chapter 8 Chromosome Structure Chromosomes
are rod-shaped structures made of DNA and protein. In eukaryotes,
DNA wraps around proteins called histones to help maintain the
compact structure of chromosomes. This allows the DNA to fit within
the cell Chapter 8 Chromosome Structure Figure 8-1 Page 151
Section 1 Chromosomes Chapter 8 Figure 8-1 Page 151 Chromosome
Structure As a cell prepares to divide, its DNA coils around
histones and twists into rod-shaped chromosomes Chromosome
Structure, continued
Section 1 Chromosomes Chapter 8 Chromosome Structure, continued
Open books to page 152, figure 8-2 Chromatids are duplicate halves
of a chromosome The point at which both chromatids are attached is
called the centromere (like the point where an X comes together)
Chromosome Structure, continued
Section 1 Chromosomes Chapter 8 Chromosome Structure, continued
Comparing chromosome structure of prokaryotes and eukaryotes
Prokaryotes (bacteria) Eukaryotes (plants and animals) simple
complex circular linear attached to cell membrane found free in
nucleus one many Chromosome Numbers of Various Organisms
Section 1 Chromosomes Chapter 8 Chromosome Numbers of Various
Organisms Each species has a characteristic number of chromosomes
in each cell. Similar to Table 8-1 on page 152 Chromosome Numbers,
continued
Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued Sex
Chromosomes and Autosomes Sex chromosomes are chromosomes that
determine the sex of an organism. In humans, sex chromosomes are
either X or Y Females XX MalesXY All of the other chromosomes in an
organism are autosomes. Chromosome Numbers, continued
Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued
Breakdown of Human chromosomes 46 chromosomes total 2 are sex
chromosomes, 44 are autosomes Karotype is a pictomicrograph of
chromosomes in a normal dividing cell found in a human Figure 8-3
on page 153 Chromosome Numbers, continued
Section 1 Chromosomes Chapter 8 Chromosome Numbers, continued 1n
Diploid cells: have two homologues of each chromosome, is
designated by the symbol 2n, and has chromosomes found in pairs
Haploid cells:are the reproductive cells or Gametes (sperm and
egg), have the number of chromosomes that are present in diploid,
and is designated by the symbol 1n 1n Chromosome Numbers,
continued
When gametes- a sperm cell (1n) and egg cell (1n) combine to create
a new organism, the new cell will be diploid (2n). If the
reproductive cells were diploid, the new cell would have too many
chromosomes and would not be functional Gametes Chapter 8
Objectives Section 2 Cell Division
Describe the events of cell division in prokaryotes. Name the two
parts of the cell that are equally divided during cell division in
eukaryotes. Summarize the events of interphase. Describe the stages
of mitosis. Compare cytokinesis in animal cells with cytokinesis in
plant cells. Explain how cell division is controlled. Cell Division
in Prokaryotes
Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes Cell
division is the process by which cells reproduce themselves.
Approximately 2 trillion cells are produced by an adult human body
every day Cell Division in Prokaryotes, continued
Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes,
continued Binary fission is the process of cell division in
prokaryotes. Remember that bacteria is considered a prokaryotehint
hint hint Page 154 Figure 8-4 Cell Division in Eukaryotes
Section 2 Cell Division Chapter 8 Cell Division in Eukaryotes Cell
Cycle The cell cycle is the repeating set of 5 events in the life
of a cell. The cell cycle consists of cell division and interphase.
Cell division in eukaryotes includes nuclear division, called
mitosis, and the division ofcytoplasm, called cytokinesis. Cell
Division in Eukaryotes,
Section 2 Cell Division Chapter 8 Cell Division in Eukaryotes, Look
at figure 8-5 page 155 Cell cycle starts at G1 and continues
through cytokinesis Correct sequence would be: G1-S-G2-M-C Make
sure you know what occurs at each of those stages Interphase
consists of growth (G1), DNA replication (S), and preparation for
cell division (G2). Occupies most of the cells life Chapter 8
Stages of Mitosis
Section 2 Cell Division Chapter 8 Stages of Mitosis Mitosis is
divided into 4 stages: prophase, metaphase, anaphase, and
telophase. Mitosis results in two offspring cells that are
genetically identical to the original cell. Follow along, pages Use
Figure 8-6, page 156 WIND UP MIDDLE Chapter 8 Stages of
Mitosis
Section 2 Cell Division Chapter 8 Stages of Mitosis Prophase 1st
phase of mitosis chromosomes grouped Centrosomes move towards poles
of the cell and start to form spindle fibers Metaphase 2nd phase of
mitosis chromosomes move to center (middle) WIND UP MIDDLE APART
TWO Chapter 8 Stages of Mitosis
Section 2 Cell Division Chapter 8 Stages of Mitosis APART Anaphase
3rd phase of mitosis Chromatids of each chromosome will split
Telophase 4th phase of mitosis Chromosomes reach opposite end of
original cell TWO Chapter 8 Stages of Mitosis Cytokinesis NOT a
phase of mitosis
Section 2 Cell Division Chapter 8 Stages of Mitosis Cytokinesis NOT
a phase of mitosis Cell splits into two cells that will be
genetically identical to original cell Section 2 Cell Division
Chapter 8 Cytokinesis During cytokinesis in animal cells, a
cleavage furrow pinches in and eventually separates the dividing
cell into two cells. In plant cells, a cell plate separates the
dividing cell into two cells after the formation of a cell wall
Chapter 8 Stages of Mitosis Put these 4 illustrations in
order
Section 2 Cell Division Chapter 8 Stages of Mitosis Put these 4
illustrations in order Looking above, which stage are the
centromeres dividing? Which illustration above shows the starting
point for mitosis? Chapter 8 Stages of Mitosis Section 2 Cell
Division
Put these 4 illustrations in order 3, 2, 1, 4 Looking above, which
stage are the centromeres dividing? 1 (Anaphase) Which illustration
above shows the starting point for mitosis? 3 (Prophase) Control of
Cell Division
Section 2 Cell Division Chapter 8 Control of Cell Division Cell
division in eukaryotes is controlled by many proteins. Control
occurs at three main checkpoints. G1: If cell is healthy and has
suitable size during G1 phase, proteins will initiate DNA
synthesis, if not healthy enough cell division stops G2: DNA repair
enzymes check the results of DNA replication, if passed they will
allow cell to continue to steps of mitosis Mitosis checkpoint:If
the cell passes this checkpoint, proteins signal the cell to exit
mitosis.The cell the enters into the G1 phase again Control of Cell
Division, continued
Section 2 Cell Division Mitosis Song Chapter 8 Control of Cell
Division, continued When Control is Lost: Cancer Cancer may result
if cells do not respond to control mechanisms. (checkpoint stops
dont work) Cancer is the uncontrolled growth of cells (tumors)
Chapter 8 Objectives Section 3 Meiosis
Compare the end products of meiosis with those of mitosis.
Summarize the events of meiosis I. Explain crossing-over and how it
contributes to the production of unique individuals. Summarize the
events of meiosis II. Compare spermatogenesis and oogenesis. Define
sexual reproduction. Formation of Haploid Cells
Section 3 Meiosis Chapter 8 Formation of Haploid Cells Meiosis -
nuclear division that reduces the number of chromosomes in new
cells to half the number in the original cell. Cells undergoing
meiosis divide twice Meiosis leads to four haploid cells or 1n
(gametes- sex cells) rather than two diploid or 2n cells as in
mitosis. 2n 2n 2n 2n 1n Section 3 Meiosis Chapter 8 Meiosis I
Meiosis I includes prophase I, metaphase I, anaphase I, and
telophase I. Make sure that you know the differences between the
meiosis and mitosis phases they do have the same names
Crossing-over- homologous chromosomes exchange genetics material
and results in genetic recombination(mixing up of DNA)
Crossing-over acts as a source of variation within a species -Each
pair of homologue chromosomes is called a tetrad.
Section 3 Meiosis Chapter 8 Follow along by looking at Figure 8-11
pages Meiosis I Prophase I: -DNA coils into chromosomes which line
up next to their homolog This pairing up is called synapsis. -Each
pair of homologue chromosomes is called a tetrad. Metaphase I:
-Tetrads line up along the middle of the cell. Chapter 8 Meiosis I
Anaphase I
Section 3 Meiosis Chapter 8 Meiosis I Anaphase I Homologous
chromosome moves to opposite pole of dividing cell The random
separation of homologous chromosomes is called independent
assortment, which results in genetic variation Telophase I and
Cytokinesis I chromosomes reach opposite end cytokinesis begins,
New cells contain haploid number of chromosomes Section 3 Meiosis
Chapter 8 Meiosis I Meiosis I original cell produces 2 new cells,
each containing 1 chromosome from each homologous pair. New cells
contain half the number of chromosomes of original cell, however,
each new cell contains two copies (as chromatids) because the
original cell copied its DNA before meiosis I Section 3 Meiosis
Chapter 8 Meiosis II Meiosis II occurs in each cell formed during
Meiosis I and is not preceded by the copying of DNA Meiosis II
includes prophase II, metaphase II, anaphase II, and telophase II
Four new haploid cells result Section 3 Meiosis Chapter 8 Meiosis
II Prophase II spindle fibers form and begin to move chromosomes
toward middle of the dividing cell Metaphase II chromosomes move to
middle of the dividing cell,-each chromatid faces opposite of the
dividing cell Chapter 8 Meiosis II Anaphase II
Section 3 Meiosis Chapter 8 Meiosis II Anaphase II chromatids
separate and move toward opposite poles of the cell Telophase II
-nuclear membrane forms around the chromosomes in each of the four
new cells Cytokinesis II four new haploid cells Each of the new
cells contain half of the original cells number of chromosomes
Section 3 Meiosis Chapter 8 Stages of Meiosis 1n 1n Chapter 8
Development of Gametes aka Sex Cells
Section 3 Meiosis Chapter 8 Development of Gametes aka Sex Cells
Spermatogenesis is the process by which sperm cells are produced.
Oogenesis is the process that produces mature egg cells. 1n 1n
Meiosis in Male and Female Animals
Section 3 Meiosis Chapter 8 Meiosis in Male and Female Animals 2n
1n Chapter 8 Sexual Reproduction
Section 3 Meiosis Meiosis Video Chapter 8 Sexual Reproduction
Sexual reproduction is the formation of offspring through meiosis
and the union of a sperm and an egg. Offspring produced by sexual
reproduction are genetically different from their parents.
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