Download Chapter 9 - kamiakinclasscalenders

Chapter 9
The Cellular Basis of Inheritance
9.1 – All Cells Come From Cells
All organisms reproduce their own kind
-Begins at cellular level
3 Functions of Cell Reproduction:
1.
Repairing Damage e.g. skin
2.
Supplying cells needed for growth
e.g. baby → child → adult
3.
Producing Offspring
9.1 Notes Continued…
2 Ways Organisms Reproduce
1.
Asexual Reproduction – simple cell division, cell duplicates
genetic material and splits into two new identical cells.
Common in plant kingdom, single celled organisms & a few
simple animals
Strawberries
produce
runners over
ground
Hydra found
in fresh water
forms a
daughter bud
9.1 Notes Continued…
2.
Sexual Reproduction – genetic material
from 2 parents combine and produce
offspring that is genetically different.
9.2 – The Cell Cycle Multiples Cells
A. Chromosomes
and Cell Division
Chromatin: genetic material in nucleus, long, thin fibers.
Chromosomes: condensed chromatin fibers

# of chromosomes depends on species. (human
body cells ~ 46)

Contains hundreds of genes
Sister Chromatids: a pair identical chromosomes created
before a cell divides.
Centromere: region where 2 sister chromatids are joined.
During cell division, sister chromatids separate, 2 cells
receive one copy of each chromosome.
9.2 Continued…
B.The Cell Cycle : Birth of cell to cell reproduction
1.
Interphase : (90% of cycle)
a)
Stage which cell carries out metabolic
functions
e.g. stomach cell making enzymes
to digest food.
b)
Cell Prepares for Division
G1 Phase: Cell grows
S phase: genetic material duplicates
G2 Phase: Cell prepares to divide
9.2 Continued…
2.
a)
b)
Mitotic Phase: (M phase)
Stage of cycle when cell is actually dividing
M phases includes 2 processes
-Mitosis: nucleus and duplicated chromosomes
divide to form 2 daughter nuclei
-Cytokinesis: cytoplasm is divided in 2
Result = 2 identical daughter cells. Each
contains a nucleus, cytoplasm & plasma memb.
9.3 – Cells Divide During the Mitotic
Phase
A.
The Mitosis Dance
Spindle: microtubules that guide chromosome
movement
Centromeres: regions of cytoplasmic material
which spindle grows from. In animal cells,
contains centrioles.
4 Main Stages of Mitosis : prophase,
metaphase, anaphase & telephase.
9.3 Continued…
1.



Prophase: (1st Stage)
Chromatin condenses and sister chromatids form
Nuclear membrane breaks down
Mitotic spindle forms, chromatids attach to spindle &
move to center of cell
9.3 Continued…
2.

Metaphase: ( 2nd Stage)
Chromosomes attached to spindle line up
across the middle of the cell
9.3 Continued…
3.

Anaphase: (3rd Stage)
Sister chromatids
separate and move
toward edges of cell
(become daughter
chromosomes)
9.3 Continued…
4.




Telophase: (4th Stage)
Spindle disappears
Two nuclear envelopes are formed
Chromosomes uncoil & again form long, thin strands.
Nucleoli reappear in the daughter nuclei
9.3 Continued…
B.
Cytokinesis in Animals and Plants
Cytokinesis = division of the cytoplasm
 Occurs during telophase
 In animal cells: microfilaments in middle of
cell pinches the cell into two
 In plant cells: cell plate forms in middle of
cell, grows and forms cell wall.
↓ Cytokinesis in a plant cell
← Cytokinesis in a animal cell
Mitosis Animations



Mitosis Example 1
Mitosis Example 2
Interactive Mitosis Tutorial
9.4 - Cancer Cells Grow and Divide
Out of Control
Tumor: Uncontrolled cell reproduction producing a
mass of cells.
Benign Tumor: Abnormal mass of normal cells.
-Can cause health problems
-Can be removed
-Stays at original site in body
Malignant Tumor: Mass of cancer cells
-Displaces normal tissue
-Can spread in body & form new tumors
9.4 Continued…
Cancer: disease caused by the disruption of
the mechanisms that control the cell cycle.
Metastasis: spread of cancer cells beyond
original site.
Different things can affect cell cycle,
therefore, there is no single “cure” but
different approaches to halt progress
9.4 Continued…
3 Forms of Cancer Treatment:
1. Removal by surgery
2. Radiation Therapy: Expose tumors to ↑ energy
radiation, disrupts cell division
-side effects can include sterility

Chemotherapy: Use drugs to disrupt cell division
by interfering w/ mitotic spindle
-Side effects can include nausea & hair loss
9.5 – Meiosis Functions in Sexual
Reproduction
Meiosis: cell division producing 4 cells, each w/ ½ # of
parent chromosomes.
animals - occurs in sex organs – testes & ovaries
# of chromosomes & types depend on species (~46
for humans or 23 pairs)
Karyotype: a display of chromosomes in a cell.
Homologous Chromosomes: the two chromosomes in
each matching pair
- same sequence of genes, however, genes may
be slightly different
9.5 Continued…
Sex Chromosomes:
chromosomes in the
23rd pair (determines
gender)
-female = XX
-male = XY (only
portions are
homologous)
Human Karyotype for a Male
9.5 Continued…
Diploid: 2 homologous sets of chromosomes
- most cells in humans
(46) = (2n), diploid #
Haploid: single set of chromosomes
-Gamates: sex cells (egg & sperm)
(23) = (n), haploid #
Fertilization: haploid egg nucleus & haploid sperm
nucleus fuse, forming diploid cell.
Zygote: fertilized egg (diploid)
9.5 Continued…
Meiosis Verses Mitosis
Meiosis: produces 4 haploid cells, exchange
of genetic material,
Mitosis: produces 2 diploid cells, no
exchange of genetic material
9.5 Continued…
Two Meiotic Divisions
Meiosis I: produces 2
haploid cells
Meiosis II: produces 4
haploid cells
Both phases are divided into
prophase, metaphase,
anaphase & telophase.
Refer to page
196-197
Prophase I: paired
homologous chromosomes
stick together in a tetrad &
crossing over occurs
Metaphase I: tetrads align
at center of the cell
Anaphase I:
sister
chromatids
stay together
and go to the
same pole
when
homologous
chromosome
s separate.
End of
Meiosis I:
chromosome
# in daughter
cells is
haploid, but
consists of
sister
chromatids.
Meiosis II: identical to mitosis. Sister chromatids
separate, each cell divides in two.
9.6 Meiosis Increases Genetic
Variation Among Offspring
1.
1.
2 Ways Meiosis Creates Genetic Variation:
# of chromosome combinations in gametes
-how chromosomes separate is chance
-# of possible combinations = 2n, n = haploid #
Crossing over- exchange of genetic material
(segments) between homologous
chromosomes.
-Occurs during Prophase I
-genetic recombination: a single chromosome
with a new combination of genetic material.
9.6 Continued…
Mitosis & Meiosis Comparison
Similarities:
Both: pass on genetic material, interphase- chromosomes duplicate
only once
Differences:
Mitosis:
 Functions in growth, repair & asexual reproduction
 Produces 2 diploid daughter cells that are genetically identical to
parent cell
Meiosis:
 Produces 4 haploid cells in organisms that reproduce sexually
 Meiosis I has key differences