Download Chapter 6 - CookNScience

Chapter 6Chromosomes and Cell
Reproduction
Mrs. Cook
Cell Organelles
Nucleus-
-
- Control center of the cell. Houses and
protects the cells genetic information, DNA.
- when the cell is not dividing DNA is in
the
form of Chromatin.
- when the cell is dividing, DNA is in
the form
of chromosomes.
Contains its own protective cover called the
Nuclear Envelope.
- Contains small channels called nuclear pores.
- RNA, made in the nucleus, moves out of the nucleus
through these pores.
Cell Organelles cont.
Nucleus cont.
- Nucleolus- location of the assembly of
Ribsomes.
Nucleus
http://www.youtube.com/watch?v=sL7bE_PA_SE
Formation of new Cells by Cell Division
• 2 Trillion Cells are produced in humans by
cell division every day!
•
Cells reproduce (cell division) for different reasons:
1. Mitosis- Growth and development- you grow from a
baby to an adult, and
Repair- if you get a cut your body produces new cells
to repair the damaged ones.
2. Formation of Gametes- we have a specialized cell
division just for making sex cells, called Meiosis.
3. Prokaryotic cells have their own type of cell divisioncalled binary fission.
Prokaryotic Cell Division
• Asexual reproduction that produces identical
offspring is called Binary Fission.
a single parent passes all of its DNA onto its
offspring
•
•
Prokaryotic cells divide this way.
Prokaryotic Cell Division
Stages of Binary Division:
1. Nucleoid (DNA) is copied so that each new cell
will have a copy of the genetic information.
2. The cell membrane develops between the
2 copies of DNA, Transverse Septum.
3. A new cell wall forms around the new
membrane.
4. The dividing cell is pinched into two new
daughter cells, each containing an exact copy of
the original DNA.
http://www.youtube.com/watch?v=DY9DNWcqxI4
Binary Fission in blepharisma
http://www.youtube.com/watch?v=l7JYvXPRPlE
Eukaryotic Cell Reproduction
• All genetic information is coded in
DNA- which is the building block of life.
• Your DNA is organized into units called
Genes.
• a single molecule of DNA has
thousands of genes lined up like a
train car.
• Each gene codes for an individual
trait. (eye color, hair texture,
freckles, etc)
Eukaryotic Cell Reproduction
• When a cell prepares to divide, the DNA forms
Chromosomes.
• Chromosomes are rod-shaped structures
made of DNA and proteins.
•
The DNA wraps tightly around proteins called
Histones, which help keep the shape of the
chromosome & the tight packaging of DNA.
Eukaryotic Cell Reproduction
• Before the DNA is coiled up,
however, the DNA is copied.
• The TWO exact copies of DNA
make up a Chromosome and give it
its “X” shape.
• Each half of the Chromosome are
called Chromatids.
• The are attached at a point called a
Centromere.
Eukaryotic Cell Reproduction
http://www.youtube.com/watch?v=9kQpYdCnU14
Eukaryotic Cell Reproduction
• When the cell is done dividing, the
chromosomes uncoil themselves, and
become a large mass of DNA. This is
called Chromatin.
Chromosome Numbers
• Eukaryotic organisms have two types of cells:
• Somatic Cells- any cell other than sperm or
egg
• Gametes- sperm and egg cells- used to
create new life.
• Every species has a specific number of
chromosomes in their somatic cells.
• Humans have 46 Chromosomes.
• Cats have 32
• Fleas have 14
Chromosome Numbers
• Humans somatic cells have 46 Chromosomes.
•
•
•
23 Pairs of Chromosomes that differ in size,
shape, and set of genes.
Each chromosome contains thousands of
genes that play an important role in
determining how a person’s body develops
and functions.
A complete set of ALL chromosomes is
essential to survival.
Chromosome Numbers
• Sex Chromosomes:
• Chromosomes that
determine the sex of an
organism.
• They can also carry genes
for other characteristics
• In Humans, they are either
X or Y
• Females have two X
chromosomes
• Males have an X and Y
chromosome.
Chromosome Numbers
• Sex Chromosomes cont:
• It is the male who determines the sex of a
fertilized egg.
X
X
XX
X
Y
XY
Warm Up 1-23-15
How many total chromosomes does a
human somatic cell contain?
What is the difference between a somatic
cell and a gamete?
What is an autosome?
If you are a girl, what sex chromosomes
do you have?
If you are a boy, what sex chromosomes
do you have?
Chromosome Numbers
• Autosomes• All other chromosomes
are referred to as
Autosomes.
•
Two of the 46 Human
chromosomes are sex
chromosomes and the
rest are autosomes.
Chromosome Numbers
• Sets of Chromosomes:
• Homologous Chromosomes• If an organism reproduces sexually, then
they have 2 copies of each chromosome.
(1 from mom & 1 from dad)
• The two copies of each autosome are
called Homologous Chromosomes or
Homologues.
• Homologues are the same size, shape &
have the same function.
Homologous
Pair
Two
Homologues
Chromosome Numbers
• Sets of Chromosomes:
• Somatic Cells- Cells that have 2 sets of
Chromosomes are Diploid.
• In humans, we have 2 copies of each of the
23 chromosomes.
• We use the abbreviation 2n to represent a
diploid number.
2n= 46
Chromosome Numbers
• If a turtle has 12 chromosomes then:
• 2n= 12
• If a flea has 14 Chromosomes then:
• 2n= 14
• If a cat has 32 chromosomes then:
• 2n= 32
Chromosome Numbers
• Sets of Chromosomes cont:
• Gametes- sperm and egg cells- each have 1
copy of each chromosomes, 23 total.
• They are said to be Haploid (half the
number of somatic cells).
• This way when an egg and a sperm join,
half of the chromosomes come from the
mother and half from the father.
• We use the letter “n” to represent a haploid
number. n=23 in humans
Haploid
Sperm (n)
Haploid
Egg (n)
Diploid Zygote
(2n)
Chromosome Numbers
• Let’s do the math!
• If humans have a total of 46 chromosomes
then
•
2n= 46
What is the number of our haploid (n)
chromosomes in the sex cells?
2(23)= 46

46= 46
then
n=23
Chromosome Numbers
• Find the number of chromosomes in the sex
cells of the following organisms: n=?
• Chicken2n= 8 chromosomes
• Chimpanzee2n=48 chromosomes
• Zebra2n=44 chromosomes
Find the number of chromosomes in the
somatic cells of the following organisms:
• Lionn= 19
• Pigeon
n= 40
• Rabbit
n= 11
Chromosome Numbers
• Karyotype
•
•
•
Is a Photomicrograph of the Chromosomes in
a normal dividing diploid cell found in a
human.
The first 22 pairs are arranged in order from
largest to smallest and are the autosomes.
The 23rd pair are the sex chromosomes.
Chromosome Numbers
• By looking at
this Karyotypeis this person,
male or female?
• Female- 2 X
chromosomes
Chromosome Numbers
• By looking at
this
Karyotype, is
this person
male or
female?
• Male- XY
chromosome
Chromosome Numbers
• By looking at this Karyotype, what is the
abnormality?
Chromosome Numbers
•
Any change in an organism’s chromosome
structure is called a Mutation.
•
•
This most often leads to death of a zygote.
It can also lead to genetic disorders, which
we will study later.
Cell Division
The Cell Cycle
• Cell Division in Eukaryotic cells is more complex
than in prokaryotic cells.
• It involves dividing the cytoplasm and the
chromosomes inside the nucleus.
• Organelles need to be rearranged before 2 new
properly functioning cells can form.
The Cell Cycle
• The Cell Cycle is a repeating sequence of
cellular growth and division during the life of an
organism.
• The cell spends 90% of its time in the first
three phases of the cycle.
• These 3 phases together are called
Interphase.
•
The cell will enter the last 2 phases of the
cycle only when it is dividing.
The Cell Cycle
• First Growth (G1) Phase:
•
•
•
•
•
•
•
•
Cell grows rapidly
Carries out normal functions
Occupies most of cells life
DNA in form of Chromatin
G1 Check Point:
If cell is healthy and large enough, certain proteins will stimulate
the cell to begin the S phase.
If not healthy enough, the cycle will stop
Some cells enter a rest period (G0). Nerve Cells remain in the
resting period and NEVER divide.
The Cell Cycle
• Synthesis (S) Phase:
• A cell’s DNA is copied (synthesis)
• DNA in the form of chromatin.
The Cell Cycle
• Second Growth (G2) Phase:
• Preparations are made for the nucleus to
divide.
•
•
Microtubules (cytoskeleton fibers) are
rearranged.
DNA, that was copied, is still in the form of
chromatin.
The Cell Cycle
• DNA Synthesis (G2) Checkpoint:
• DNA replication is checked at this point.
• If this checkpoint is passed, proteins help to
trigger Mitosis.
The Cell Cycle
• Mitosis (M) Phase:
•
The process during cell division in which the nucleus
of a cell is divided into two nuclei.
•
•
Each nuclei ends up with the same number of and
kinds of chromosome as the original cell.
Cytokinesis:
• The process during cell cycle in which the
cytoplasm divides.
The Two New cells at the end of The Cell Cycle are
called Daughter Cells.
The Cell Cycle
• Mitosis (M) Checkpoint.
• Triggers the exit from Mitosis and signals the
beginning of the G1 phase in the two new
daughter cells.
Mitosis
• Mitosis is broke into 4 Stages:
• Prophase
• Metaphase
• Anaphase
• Telophase
•
Cytokinesis begins part way through
Telophase and completes after Telophase.
Mitosis
• Prophase:
•
•
DNA coils into
chromosomes and
chromatids are visible.
The nucleolus and
nuclear membrane
disappear.
Sister Chromatids
Mitosis- Prophase
• Prophase cont:
• Centrosomes appear next to the
disappearing nucleus
• In animal cells, each centrosomes contains
a pair of small cylindrical bodies called
centrioles
• In plant cells, the centrosome lack
centrioles.
• The Centrosomes move toward the
opposite poles of the cell.
Mitosis- Prophase
Centrosomes with Centrioles
moving towards poles
Nucleolus disappeared
and nuclear membrane
breaking down
Sister Chromatids
are visible
attached by
centromeres
Mitosis- Prophase
Mitosis- Prophase
• In Late Prophase, As the Centrosomes
separate, Spindle Fibers made of microtubles
form.
• These fibers will be responsible for pulling the
chromotids apart.
Mitosis- Metaphase
• Metaphase (“Meta” means Middle):
•
•
Chromosomes are easy to see in this phase,
theresfore most karyotypes are of cells in
Metaphase.
Spindle Fibers
• move the chromosomes to the center of the
cell and line up along the equator.
• They then link the chromatids of each
chromosome to opposite poles.
Mitosis- Metaphase
Mitosis- Metaphase
Mitosis- Anaphase
• Anaphase:
•
•
The Chromatids separate at the centromere
and slowly move, the centromere first, toward
opposite poles.
After the chromotids separate, they are
considered to be individual chromosomes.
Mitosis- Anaphase
Mitosis- Anaphase
Mitosis- Telophase
• Telophase:
•
•
•
•
•
Once the chromosomes are at opposite poles,
the spindle fibers disappear
The chromosomes return to their chromatin
state.
A nuclear envelope forms around each new
set of chromosomes.
A nucleolus forms in each of the newly formed
cells.
Cell membrane begins to pinch inward.
Mitosis- Telophase
Mitosis- Telophase
Cytokinesis
• Cytokinesis:
•
•
The division of the cytoplasm (which begins at
the very end of telophase).
In Plant Cells
• A Cell Plate is formed in the middle of the dividing
cell, which eventually develops into a new cell wall,
separating the two new cells
•
In Animal Cells
• Cell membrane pinches inward forming a
Cleavage Furrow.
Cytokinesis
Cytokinesis- Plant Cells
Cytokinesis- Animal Cells
Mitosis
Prophase
Metaphase
Interphase
Anaphase
Telophase
https://www.youtube.com/watch?v=L0k-enzoeOM
http://www.youtube.com/watch?v=VlN7K1-9QB0
http://www.youtube.com/watch?v=C6hn3sA0ip0
When Control is lost: Cancer
• Mutations can cause proteins at the
checkpoints to not work properly.
• Cell growth and division can be disrupted.
• These disruptions can lead to cancer,
which is the uncontrolled growth of cells.
• Cancer is a disorder of cell division.
1. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
2. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
3. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
4. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
5. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
6. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
What Structure is
forming?
7. Identify the following phase of Mitosis as
Prophase, Metaphase, Anaphase or
Telophase
A
B