5.4 Asexual Reproduction KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal...
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Transcript of 5.4 Asexual Reproduction KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal...
5.4 Asexual Reproduction
KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.
5.1 Cell Cycle
5.4 Asexual Reproduction
KEY CONCEPTCell 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.
5.3 Regulation of the Cell Cycle
5.4 Asexual Reproduction
Cell size is limited.• If volume increases faster than surface area then cell
divides– Surface area to Volume Ratio
5.1 Cell Cycle
5.4 Asexual Reproduction
– a normal feature of healthy organisms– occurs in development of infants
webbed fingers
• Apoptosis is programmed cell death.
5.3 Regulation of the Cell Cycle
5.4 Asexual Reproduction
– 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
Asexual reproduction is the creation of offspring from a single parent.
5.4 Asexual Reproduction
• Budding forms a new organism from a small projection growing on the surface of the parent.
bud
Hydra
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
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
5.1 Cell Cycle
5.4 Asexual Reproduction
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
5.2 Mitosis and Cytokinesis
5.4 Asexual Reproduction
2. Metaphase• Chromosomes line up in the middle of the cell. • Chromosomes are easier to identify• Photomicrograph for Karyotype
5.2 Mitosis and Cytokinesis
5.4 Asexual Reproduction
3. Anaphase• sister chromatids separate to opposite sides of
the cell.
5.2 Mitosis and Cytokinesis
5.4 Asexual Reproduction
4. Telophase• New nucleus and nucleolus form • Chromosomes begin to uncoil • Spindle fibers and centrioles disappear
5.2 Mitosis and Cytokinesis
5.4 Asexual Reproduction
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 and Cytokinesis
5.4 Asexual Reproduction
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
5.2 Mitosis and Cytokinesis
5.4 Asexual Reproduction
KEY CONCEPT During Meiosis, diploid cells undergo two cell divisions that result in 4 different haploid cells.
6.2 Process of Meiosis
5.4 Asexual Reproduction
• Meiosis – Division of nucleus which makes haploid cells from diploid cells.
– Occurs in sex organs – Produces genetically different sex cells - gametes.
6.1 Chromosomes and Meiosis
5.4 Asexual Reproduction
Stages of MeiosisInterphase – 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
6.2 Process of Meiosis
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 #)
6.6 Meiosis and Genetic Variation
5.4 Asexual Reproduction
• DNA is not replicated between meiosis I andmeiosis II (No Interphase)
6.2 Process of Meiosis
5.4 Asexual Reproduction
Meiosis II
1. Prophase II• Spindle fibers and centrioles form 2. Metaphase II• Chromosomes move to the middle of the cells3. Anaphase II• Chromatids separate & move toward opposite poles4. Telophase II• Nuclear membrane forms around the chromosomesCytokinesis II – results in 4 new cells each with half the # of chromosomes
6.2 Process of Meiosis
5.4 Asexual Reproduction
– Meiosis has two cell divisions - mitosis has one– Meiosis results in 4 haploid cells - mitosis results in 2
diploid cells
6.2 Process of Meiosis
5.4 Asexual Reproduction
After Meiosis Haploid cells develop into mature gametes.
• Gametogenesis - the production of gametes.
• Gametogenesis differs between females and males.
6.2 Process of Meiosis
5.4 Asexual Reproduction
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
6.2 Process of Meiosis
5.4 Asexual Reproduction
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)
6.2 Process of Meiosis