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


Cells divide at different rates.

5.1 Cell Cycle


KEY CONCEPTCell cycle regulation is necessary for healthy growth.

5.3 Regulation of the Cell Cycle


• External factors include physical and chemical signals.• Growth factors are proteins that stimulate cell division.



Cell size is limited.• If volume increases faster than surface area then cell

divides– Surface area to Volume Ratio

5.1 Cell Cycle


– a normal feature of healthy organisms– occurs in development of infants

webbed fingers

• Apoptosis is programmed cell death.



KEY CONCEPTMany organisms reproduce by cell division.


– 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.


• Budding forms a new organism from a small projection growing on the surface of the parent.

bud

Hydra

Yeast


• Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.


The Cell Cycle has Three main stages.

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

5.1 Cell Cycle


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


2. Metaphase• Chromosomes line up in the middle of the cell. • Chromosomes are easier to identify• Photomicrograph for Karyotype



3. Anaphase• sister chromatids separate to opposite sides of

the cell.



4. Telophase• New nucleus and nucleolus form • Chromosomes begin to uncoil • Spindle fibers and centrioles disappear



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



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



KEY CONCEPT During Meiosis, diploid cells undergo two cell divisions that result in 4 different haploid cells.

6.2 Process of Meiosis


• 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


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


5.4 Asexual Reproduction6.6 Meiosis and Genetic Variation


Metaphase I

• Tetrads line up randomly along the middle of the cell

6.6 Meiosis and Genetic Variation


Anaphase I

• Tetrads separate• Each homologous chromosome moves to an opposite

pole• Independent Assortment – random separation of the

homologous = genetic recombination



Telophase I

• Chromosome reach the opposite pole• Cytokinesis begins• Each new cells now contains a haploid # of

chromosomes (half the original #)



• DNA is not replicated between meiosis I andmeiosis II (No Interphase)



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



– Meiosis has two cell divisions - mitosis has one– Meiosis results in 4 haploid cells - mitosis results in 2

diploid cells



After Meiosis Haploid cells develop into mature gametes.

• Gametogenesis - the production of gametes.

• Gametogenesis differs between females and males.



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



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

5.4 asexual reproduction key concept cells have distinct phases of growth, reproduction, and normal...

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