Download Chapter 6 - River Ridge #210

Chapter 6- Chromosomes and
Cell Reproduction
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I. Chromosomes
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A. New cells are formed by
cell division.
1.
2.
3.
An adult human body produces about 2
trillion cells EVERY day! This is about 25
million new cells per second!
Cell division allows for this.
Eukaryotic organisms undergoing growth,
development, repair, or asexual reproduction
divide by a different type of cell division.
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4. Gametes are reproductive cells (egg
and sperm) undergo meiosis for cellular
division.
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B. Bacterial cells divide to
reproduce
1.
Bacteria reproduce by a type of cell
division called binary fission.
2.
Binary fission is a form of asexual
reproduction that produces identical
offspring.
3. In asexual reproduction a single parent
passes exact copies of its entire DNA to its
offspring.
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C. Eukaryotic cells form
chromosomes before cell division
1. A gene is a segment of DNA that
codes for a protein or RNA molecule.
2. As a Eukaryotic cell prepares to divide,
the DNA and the proteins associated
with DNA coil into a structure called
chromosomes.
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3. Chromosomes are squished together
called chromatids.
4. The chromosome has two strands –
one from mom and one from dad. A
“twist tie” called a centromere holds
them together. See page 119.
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Centromere
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D. Chromosome number and
structure affect development.
1.
Each human somatic (any cell besides sex
cells) normally contain two copies of 23
chromosomes for a total of 46 chromosomes.
2.
Each chromosome contains thousands of
genes that play important roles in
determining how a person’s body develops
and functions.
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3. Each of the 23 pairs of chromosomes
consists of two homologous
chromosomes.
4. Homologous chromosomes are
chromosomes that are similar in size,
shape and genetic content.
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5. All of the cells in the body, besides
gametes have two pairs of
chromosomes. (One from mom one
from dad) they are called diploid.
6. Sex cells only have DO NOT have a
pair, they are called haploid (1/2 the
amount of chromosomes)
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7. A zygote is a fertilized egg cell.
8. Look at figure 6-1 pages 121 to view
number of chromosomes.
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E. Chromosomes determine
your sex.
1.
Of the 23 pairs of chromosomes in human
somatic cells, 22 pairs are called autosomes
2.
Autosomes are chromosomes that are not
directly involved in determining the sex of an
individual.
3.
The sex chromosomes, one of the 23 pairs
contain the gene that determines the gender.
Males determine the gender of the human.
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F. Change in chromosome
number
1.
Sometimes a human could have
different chromosome numbers.
2.
A karyotype is performed to view an
individual’s chromosomes.
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3.
Down syndrome is an extra copy on
pair 21.
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II. The cell Cycle
A. The cell cycle describes the life of a
Eukaryotic cell.
1.
The cell cycle is a repeating sequence of
cellular growth and division during the life of
an organism.
2.
A cell spends 90% of its time in the first
three phases of the cycle-interphase.
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3. First growth (G1)phase- a cell grows rapidly
and carries out its routine functions. Cells
that are not dividing remain in the G1 phase.
4. Synthesis (S) phase- A cell’s DNA is copied
during this phase. At the end of this phase,
each chromosome consists of two chromatids
attached at the centromere.
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5. Second growth (G2) phase-In the G2
phase, preparations are made for the
nucleus to divide.
6. Mitosis-the process during cell division
in which the nucleus of a cell is divided
into two nuclei.
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7. Each nucleus ends up with the same
number and kinds of chromosomes as
the original cell.
8. Cytokinesis-the cytoplasm splits.
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B. The cell cylce is carefully
controlled
1.
If a cell spends 90% of its time in interphase how do cells
“know” when to divide?
2.
Cell Growth (G1) checkpoint-This checkpoint makes the
key decision of weather the cell will divide or not.
3. DNA synthesis (G2) checkpoint-DNA replication is checked
at this point by DNA repair enzymes. If this checkpoint is
passed, proteins help to trigger mitosis.
4. Mitosis checkpoint-will trigger the exit from mitosis.
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C. When control is lost:
cancer
1.
Certain genes contain the
information necessary to make the
proteins that regulate cell growth and
division.
2.
If one of these genes is mutated,
the protein may not function.
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3. Cancer is the uncontrolled growth of
cells.
4. Cancer is a disorder of cell division.
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D. Mitosis
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Interphase (not really a phase)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
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INTERPHASE
Interphase- is part of the cell cycle before
mitosis. During Interphase
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The cell grows
DNA is being copied
This period between cell division can be very long.
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INTERPHASE
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PROPHASE
Prophase- This is the longest phase.
During this phase;
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The nuclear envelope disappears.
The centrioles start to move to the opposite
poles.
Spindle fibers start to form.
Chromosomes are becoming evident.
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PROPHASE
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METAPHASE
Metaphase-Metaphase is the shortest
phase of mitosis.
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The chromosomes line up in the middle of the
cell.
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METAPHASE
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ANAPHASE
ANAPHASE- Begins when the
centromere that join the sister
chromatids start to split.
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The chromosomes are being pulled to the
opposite sides of the cell toward the Centrioles.
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ANAPHASE
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TELOPHASE
TELOPHASE-Final process of mitosis.
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Chromosomes are at the opposite poles.
Nuclear envelope reforms.
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TELOPHASE
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CYTOKINESIS-Splitting of the
cytoplasm.
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Teacher note:
http://www.cellsalive.com/mitosis.htm
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THE END
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