Transcript 5.4 Asexual Reproduction

5.4 Asexual Reproduction
5.1 Cell Cycle
KEY CONCEPT
Cells have distinct phases of growth, reproduction,
and normal functions.
5.4 Asexual Reproduction
5.1 Cell Cycle
Cells divide at different rates.
5.3
Regulation
of the Cell Cycle
5.4 Asexual
Reproduction
KEY CONCEPT
Cell cycle regulation is necessary for healthy growth.
5.3
Regulation
of the Cell Cycle
5.4 Asexual
Reproduction
• External factors include physical and chemical signals.
• Growth factors are proteins that stimulate cell division.
5.4 Asexual Reproduction
5.1 Cell Cycle
Cell size is limited.
• If volume increases faster than surface area then cell
divides
– Surface area to Volume Ratio
5.3
Regulation
of the Cell Cycle
5.4 Asexual
Reproduction
• Apoptosis is programmed cell death.
– a normal feature of healthy organisms
– occurs in development of infants
webbed fingers
5.4 Asexual Reproduction
KEY CONCEPT
Many organisms reproduce by cell division.
5.4 Asexual Reproduction
Asexual reproduction is the creation of offspring from a
single parent.
– Binary fission produces two daughter cells genetically
identical to the parent cell.
– occurs in prokaryotes
- No nucleus
- Ex: bacteria
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells
5.4 Asexual Reproduction
• Budding forms a new organism from a small projection
growing on the surface of the parent.
Hydra
bud
Yeast
5.4 Asexual Reproduction
• Vegetative reproduction forms a new plant from the
modification of a stem or underground structure on
the parent plant.
5.4 Asexual Reproduction
5.1 Cell Cycle
The Cell Cycle has Three main stages.
5.4 Asexual Reproduction
5.1 Cell Cycle
1. Interphase
• Gap 1 (G1) – cell growth and
normal functions
• Synthesis (S): copies DNA
• Gap 2 (G2): additional
growth
2. Mitosis (M)
• Division of the cell nucleus
3. Cytokinesis
• Division of the cell cytoplasm
Some cells (G0) – exit the cell cycle
• fully developed cells in the CNS
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
Mitosis divides the cell’s nucleus in four phases.
1. Prophase
• chromosomes condense and spindle fibers
form
• Nucleolus and the nuclear membrane break
down & disappear
• Centrioles (centrosomes) appear
5.4 Asexual Reproduction
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
2. Metaphase
• Chromosomes line up in the middle of the cell.
• Chromosomes are easier to identify
• Photomicrograph for Karyotype
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
3. Anaphase
• sister chromatids separate to opposite sides of
the cell.
5.4 Asexual Reproduction
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
4. Telophase
• New nucleus and nucleolus form
• Chromosomes begin to uncoil
• Spindle fibers and centrioles disappear
5.4 Asexual Reproduction
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
Cytokinesis differs in animal and plant cells.
• Cleavage furrow (animal cells) the cell
membrane pinches in
• Cell plate (plant cells) a cell wall
forms between the two
cells
5.2
Mitosis Reproduction
and Cytokinesis
5.4 Asexual
Results of Mitosis
•
•
•
•
2 new cells genetically identical to the parent cell
2 identical diploid cells.
Single celled eukaryote – asexual reproduction
Multi-celled eukaryote – growth
5.4
Reproduction
6.2Asexual
Process
of Meiosis
KEY CONCEPT
During Meiosis, diploid cells undergo two cell
divisions that result in 4 different haploid cells.
5.4 Asexual
Reproduction
6.1
Chromosomes
and Meiosis
• Meiosis – Division of nucleus which makes haploid
cells from diploid cells.
– Occurs in sex organs
– Produces genetically different sex cells - gametes.
5.4
Reproduction
6.2Asexual
Process
of Meiosis
Stages of Meiosis
Interphase – G1, S, G2
Meiosis I
1.
Prophase I
•
•
•
•
DNA coils tightly into chromosomes
Spindle fibers & centrioles appear
Nucleus & nucleolus disappear
Synapsis - Every chromosome lines up next to its
homologue
– each pair is called a tetrad – 4 chromatids
XX
– during synapsis the chromatids twist around each other
– crossing over - portions of chromatids may break off &
attach to adjacent chromatids
-
* genetic recombination - the exchange of genetic material
between maternal & paternal chromosomes
6.6
Meiosis and
Genetic Variation
5.4 Asexual
Reproduction
6.6
Meiosis and
Genetic Variation
5.4 Asexual
Reproduction
Metaphase I
• Tetrads line up randomly along the middle of the cell
6.6
Meiosis and
Genetic Variation
5.4 Asexual
Reproduction
Anaphase I
• Tetrads separate
• Each homologous chromosome moves to an opposite
pole
• Independent Assortment – random separation of the
homologous = genetic recombination
6.6
Meiosis and
Genetic Variation
5.4 Asexual
Reproduction
Telophase I
• Chromosome reach the opposite pole
• Cytokinesis begins
• Each new cells now contains a haploid # of
chromosomes (half the original #)
5.4
Reproduction
6.2Asexual
Process
of Meiosis
• DNA is not replicated between meiosis I and
meiosis II (No Interphase)
5.4
Reproduction
6.2Asexual
Process
of Meiosis
Meiosis II
1.
Prophase II
•
Spindle fibers and centrioles form
2.
Metaphase II
•
Chromosomes move to the middle of the cells
3.
Anaphase II
•
Chromatids separate & move toward opposite poles
4.
Telophase II
•
Nuclear membrane forms around the chromosomes
Cytokinesis II – results in 4 new cells each with half the # of chromosomes
5.4
Reproduction
6.2Asexual
Process
of Meiosis
– Meiosis has two cell divisions - mitosis has one
– Meiosis results in 4 haploid cells - mitosis results in 2
diploid cells
5.4
Reproduction
6.2Asexual
Process
of Meiosis
After Meiosis Haploid cells develop into mature gametes.
• Gametogenesis - the production
of gametes.
• Gametogenesis differs between
females and males.
5.4
Reproduction
6.2Asexual
Process
of Meiosis
Spermatogenesis – production of sperm cells
• Meiosis = Diploid reproductive cell divides to form four
haploid cells – spermatids
• Each spermatid then develops into a mature sperm cell
• sperm cells (plural) – spermatozoa
5.4
Reproduction
6.2Asexual
Process
of Meiosis
Oogenesis – production of mature egg cells – ova (plural)
• Meiosis = Diploid reproductive cell divides to produce one
mature egg cell (ovum)
• During cytokinesis the cytoplasm of the cell is divided
unequally
• One cell receives most of the cytoplasm  develops into
ovum
• Other 3 cells = polar bodies = degenerate (break down)
13.1 Ecologists Study Relationships
Genetic Disorder Topic Due:
Monday November 18