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The Cell Cycle PowerPoint PPT Presentation


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The Cell Cycle. The Cell Theory: All organisms consist of cells and arise from preexisting cells. Mitosis is the process by which new cells are generated. Meiosis is the process by which gametes are generated for sexual reproduction. Cell and Chromosome Structure.

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The Cell Cycle

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The Cell Cycle


The cell theory all organisms consist of cells and arise from preexisting cells l.jpg

The Cell Theory: All organisms consist of cells and arise from preexisting cells

  • Mitosis is the process by which new cells are generated.

  • Meiosis is the process by which gametes are generated for sexual reproduction.


Cell and chromosome structure l.jpg

Cell and Chromosome Structure

  • Prokaryotic cells have no nucleus

  • DNA is organized into one circular chromosome

Ribosomes

Flagella

Cytoplasm

Chromosome

Chromosome

Cell membrane

Cell wall


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Cell and Chromosome Structure

  • In eukaryotic cells, the genetic material is found within a membrane-bound nucleus

  • DNA is organized into multiple linear shaped chromosomes

Chromosome

Nucleus

Nuclear membrane

Cell membrane

Cytoplasm


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DNA is packaged into chromosomes


Eukaryotic chromosomes may be in their unreplicated or unreplicated state l.jpg

Eukaryotic chromosomes may be in their unreplicated or unreplicated state

Sister chromatids

DNA replication

Centromere

One chromosome

(Unreplicated state)=

One-double stranded DNA molecule

One chromosome

(Replicated state)=

Two double stranded DNA molecules


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Chromosomes in cells

  • All individuals of a particular species have a characteristic number of chromosomes

    • Fruit flies have 8 chromosomes in their nuclei

    • Humans have 46 chromosomes in their nuclei

  • Chromosomes of most species come in pairs

One pair of homologous chromosomes-

Replicated state

One pair of homologous chromosomes-

Unreplicated state


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Homologous chromosomes

  • Each member of a pair of homologous chromosomes:

    • Same size

    • Same shape, centromere location

    • Same genetic loci = physical location of a gene on a chromosome

Gene for eye color

Gene for eye color

One pair of homologous chromosomes


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Homologous chromosomes

  • But:

    • Each member of the pair (each “homolog”) may carry different versions of the gene

    • Different versions of the same gene = alleles

      • Eye color gene:

        • Brown allele

        • Blue allele

Brown eye allele

Blue eye allele


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A cell with 2 pairs of homologous chromosomes

Eye color gene:B= brown eye allele

b= blue eye allele

Height gene: T= tall allele

t= short allele

b

b

B

b

DNA

replication

T

B

B

t

t

T

T

t


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Ploidy: chromosomes don’t always come in pairs

  • Haploid = a cell with only one of each kind of chromosome

  • Diploid = a cell with two of each kind of chromosome

  • Triploid = a cell with three of each kind of chromosome

2n = 4

3n = 6

1n = 2

Number of

each type

of chromosome

How many different

kinds of chromosome

Total number of

chromosomes


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A cell that is 2n = 4

Unreplicatedchromosomes

Chromosome

Number of chromosomes: 4


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A cell that is 2n = 4

Replicated chromosomes

Chromosome

Sisterchromatids

Centromere

Number of chromosomes: 4


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Humans are diploid

23 pairs of chromosomes:

2n = 46


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Overview of Mitosis:

Parent cell

Replicated chromosomescondense at the start of mitosis

Mitosis

Sister chromatids separate and two daughter cells are formed.

Parent cell and daughter cell contain thesame complement of chromosomes.


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The cell cycle represents all phases in the life of a cell

  • Interphase:

    • DNA replication (S phase) must precede mitosis so that all daughter cells receive the same complement of chromosomes as the parent cell.

    • The Gap phases separate mitosis from S phase. This is the time when molecular signals mediate the switch in cellular activity.

  • Mitosis: division of nucleus

  • Cytokinesis: division of cytoplasm


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The cell cycle:


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Functions of Mitosis

  • Mitosis produces genetically identical cells

  • Purpose

    • Asexual Reproduction

    • Growth and Development

    • Tissue repair


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Asexual Reproduction in Amoeba


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Growth and development

1-celled zygote

(2n)

mitosis

Sand dollar embryo

Multi-cellular adult (2n)


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Tissue renewal

Dividing bone marrow cells give rise to new blood cells


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