The Nucleus Asexual Reproduction: Mitosis & Cell Division.
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Transcript of The Nucleus Asexual Reproduction: Mitosis & Cell Division.
The NucleusAsexual Reproduction:
Mitosis &
Cell Division
General Info:
Nucleus:
–the “brain” of the cell
–controls the cells activities
–responsible for cell division, protein synthesis
General Info Cont.
Nucleus:–contains genetic material called
DNA
–DNA long chain (chromatin) of genetic information (eukaryotes)
–In prokaryotes (bacteria) DNA is in the shape of a ring called a
plasmid
Chromatin
Nucleolus
Nucleus
Chromosomes:
–made of Deoxyribonucleic Acid DNA wrapped around proteins
–Chromosomes in eukaryotes are “rod shaped” structures made of DNA and proteins
Chromosomes:
• consist of 2 halves called chromatids
• “sister chromatids” are connected in the center by a centromere
Chromosome
(Coiled chromatin)
Ck question
Topic: DNA and Chromosomes
Date: 1-4-2010
1. Genetic material of a cell is called …
2. The location of #1
3. The ring of DNA found in Bacteria is…
4. Chromosomes consist of 2 halves known as…
Chromosome Numbers:
• Each species has a characteristic number of chromosomes in each cell.
• ex. Fruit flies (drosophila) = 8
chromosomes
• horse has 64 chromosomes
• humans have 46 and chimpanzees have 48 chromosomes
From 7 characteristics of living things:
All living things Grow
• Growth occurs from the division of cells.
• Cell Division (cellular reproduction) allows cells to:
1.Grow in size
2.Grow in number
3.Replace worn out, injured or dying cells
2 Forms of Cellular Reproduction (cell division):
1. Asexual Reproduction involves only one parent cell
a. Occurs in Autosomes or somatic cells … body cells
b. Plants/animals
2 Forms of Cellular Reproduction (cell division) Cont…
c. protists (protozoan) = single celled organisms
(binary fission)d. fungi
e. bacteria = binary fission
2 Forms of Cellular Reproduction (cell division):
2.Sexual Reproduction
involves 2 parents cellsa. Gametes = sex cells
b. Making gametes!!!
Sexual reproduction:
Occurs in sperm cells and egg cells
The Cell CycleAsexual Reproduction aka MITOSIS
The Cell Cycle is responsible for:
– birth and death of a cell– Cell division of nucleus, home of
hereditary information…chromosomes
– Cell division (Cell Cycle) consists in 3 processes
Cell Cycle consists in 3 processes
1. Interphase2. Division of the nucleus=
mitosis3. Division of the cytoplasm = cytokinesis
Ck questionTopic: Cell reproduction
Date: 1-4-2010
1. How many chromosomes does a normal humans have?
2. Identify 3 reasons cells divide.
3. The 2 types of cellular reproduction are…
4. Define gametes.
5. Define autosome.
Before a cell divides….
Interphase (nucleus)
• Cell spends most time here
Interphase:• Divided into 3 phases
1. G1 – cells grow to mature size
2. S – DNA is copied or duplicated
called DNA replication
1. G2 – cell prepares to divide
• Some cells have a G0 phase, they do not replicate after maturity. Ex. Nervous System
Mitosis:
One cell (PARENT CELL) divides into
2 identical cells (Daughters) – divisions: nucleus divides
– a series of chronological steps:
1. prophase
2. metaphase
3. anaphase
4. telophase
Division of the nucleus (DNA)!!
Mitosis
Prophase:
• Chromatin condenses, becomes visible strands of DNA called chromosomes
• 2 chromosomes are made of “sister chromatids”
• chromatids are connected by centromere
• centrioles in animal cells begin to separate (opposite ends or poles)
Prophase Cont.
• spindle fibers form (football shape) from the centrioles and connect to centromere of each chromatid
• nuclear membrane fades
• chromatids (chromosomes) begin moving to center
CentriolesSpindle fibers
Chromosomes Centromere
Metaphase: (middle)
• chromosomes (chromatids) line up in the middle of the cell
• centromere divide
• chromosomes are pulled apart separate chromosomes (???)
Chromosome
Centromere
Spindle fibers
Anaphase: (away)
• centromere divides
• chromatids separate
• move to opposite ends of cell
• complete set of chromatids go to each pole
chromatid
Telophase:
• final step of mitosis
• chromatids unwind, spindle fibers disappear
• nuclear membrane forms around each of chromatids
Cytokinesis:
• final step in the cell cycle
• cytoplasm (and organelles) divide equally in cells
• animals-pinching in of the cell membrane forming a cleavage furrow
• plants - cell plate forms across the middle growing outward
In animal cells
• (begins outside the cell)
In plate cells
• (begins inside the cell)
Results of Mitosis:• division of the nucleus (Asex. Reprod.)• products are 2 new cells with identical
information to each other and to the parent cell
• most cells reproduce asexually mitosis– ex. Of cells produced through mitosis
include:
in animals: blood cells, skin cells, cheek cells,
in plants: root cells, stem cells, leaves
Parent Cell
Identical Daughter Cells
Identical Daughter CellsIdentical Daughter Cells
Parent CellParent Cell
Two identical Two identical daughter daughter
cellscells