BIOLOGY 1Cell Cycle

Cell Review

Cell Theory:

* All living things composed of cells

* Cells are the basic units of structure and function in living things.

* New cells are produced from existing cells

Cell Review

Nucleus of the Cell:Controls most cell processes and contains the hereditary information. This is found as Deoxyribonucleic Acid (DNA)

Chromatin: DNA bound to protein – granular and visible in the nucleus.Chromosomes: Chromatin that condenses in preparation for cell division.DNA: Coded instructions for making proteins.

Cell Review

Microtubules: They aide in cell division, separating chromosomes (known as centrioles in animal cells).

Cell Division

PROKARYOTE CELL DIVISION

EUKARYOTE CELL DIVISION

Asexual Reproduction Growth and replacement of old and/or dying cells

DNA = One Circular Chromosome and Plasmids

DNA = 10-50 chromosomes per cell

Humans = 46 (23 identical pairs)

Cell Division called the Cell CycleCell Division called Binary Fission

Cell ReplicationCell Cycle:

Phase 1: Interphase

Phase 2: Mitosis

Phase 3: Cytokinesis

G1 - primary growth phaseS – synthesis; DNA replicatedG2 - secondary growth phase

Cell Replication (Cell Cycle)

Phase 1: InterphaseG1 - primary growth phase

S – synthesis; DNA replicated

G2 - secondary growth phase

Cell Matures: Growth and Organelles

DNA copied/replicated

Cell Structures needed for division made Centrioles

Mitosis: Prophase

Chromatin condenses into chromosomes Mitotic spindle forms and attaches to

centromeres Nuclear membrane/nucleolus broken

down.

Mitosis: Prophase

dissolving

Centrioles

Mitosis: Metaphase

Chromosomes line up at the equator of the cell

Mitosis: MetaphaseCentriole

Centriole

CentromereEquator

Mitosis: Anaphase

Sister Chromatids pulled apart to opposite poles of the cell.

Anaphase

Equator

Review

Mitosis: Telophase

Sister Chromatids completely at opposite poles

Nuclear envelope forms Nucleolus appears Cytokinesis occurs

Mitosis: Telophase

Equator

Cell Replication (Cell Cycle)

Phase 3: Cytokinesis

Division of cell into two – Division of the cytoplasm by a

cleavage furrow

Cleavage Furrow

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Name the Stages of Mitosis:

Interphase

Early prophase

Mid-ProphaseLate Prophase

Metaphase

Late Anaphase

Early Anaphase

Early Telophase, Begin cytokinesis

Late telophase, Advanced cytokinesis

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Cell ChromosomesKaryotype A picture of the

chromosomes from a human cell arranged in pairs by size

First 22 pairs are called autosomes

Last pair are the sex chromosomes

XX female or XY male

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Boy or Girl?

Y - Chromosome

X - Chromosome

The Y Chromosome Decides

Meiosis – Formation of Gametes

(Eggs and Sperm)

Spermatogenesis (formation of sperm)

Females:

Males:

Oogenesis (formation of eggs)

Two Stages: Meiosis I and Meiosis IIDuring Meiosis I – Homologs form Tetrads and crossing over occurs, all resulting cells are still diploid (2N) 46 chromosomes

During Meiosis II – Chromosomes are split and all cells become haploid (1N) 23 chromosomes

Why is this important?Entire process called reduction division

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Homologs form Tetrads Homologous chromosomes(compare to sister chromatids)  

Join to form a tetrad

Called Synapsis

(compare to a centromere)

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Crossing-Over Homologous

chromosomes in a tetrad cross over each other

Pieces of chromosomes or genes are exchanged

Produces Genetic recombination in the offspring

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Crossing-over multiplies the already huge number of different gamete types

Crossing-Over

Cell Cycle and Meiosis

Lets compare Mitosis and Meiosis –

What do you know?

46 chromatids(92

chromosomes, paired after replication – held by a synapsis/centromere)

46 chromosomes each side

Mitosis: 46

chromosomesMeiosis: 23

chromosomes

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Mitosis Meiosis

Number of divisions

12

Number of daughter cells

2 4

Genetically identical?

Yes No

Chromosome #Same as parent

Half of parent

Where Somatic cells Germ cells

WhenThroughout

lifeAt sexual maturity

RoleGrowth and

repairSexual

reproduction

Comparison of Divisions