The Cell Cycle
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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 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 from preexisting cells

  • Prokaryotic cells have no nucleus

  • DNA is organized into one circular chromosome

Ribosomes

Flagella

Cytoplasm

Chromosome

Chromosome

Cell membrane

Cell wall


Cell and chromosome structure4 l.jpg
Cell and Chromosome Structure from preexisting cells

  • 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


Dna is packaged into chromosomes l.jpg
DNA is packaged into chromosomes from preexisting cells


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


Chromosomes in cells l.jpg
Chromosomes in cells unreplicated state

  • 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


Homologous chromosomes l.jpg
Homologous chromosomes unreplicated state

  • 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


Homologous chromosomes9 l.jpg
Homologous chromosomes unreplicated state

  • 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


A cell with 2 pairs of homologous chromosomes l.jpg
A cell with 2 pairs of homologous chromosomes unreplicated state

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


Ploidy chromosomes don t always come in pairs l.jpg
Ploidy: chromosomes don’t always come in pairs unreplicated state

  • 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


A cell that is 2n 4 l.jpg
A cell that is 2n = 4 unreplicated state

Unreplicatedchromosomes

Chromosome

Number of chromosomes: 4


A cell that is 2n 413 l.jpg
A cell that is 2n = 4 unreplicated state

Replicated chromosomes

Chromosome

Sisterchromatids

Centromere

Number of chromosomes: 4


Humans are diploid l.jpg
Humans are diploid unreplicated state

23 pairs of chromosomes:

2n = 46


Overview of mitosis l.jpg
Overview of Mitosis: unreplicated state

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.


The cell cycle represents all phases in the life of a cell l.jpg
The cell cycle represents all phases unreplicated statein 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


The cell cycle l.jpg
The cell cycle: unreplicated state


Functions of mitosis l.jpg
Functions of Mitosis unreplicated state

  • Mitosis produces genetically identical cells

  • Purpose

    • Asexual Reproduction

    • Growth and Development

    • Tissue repair


Asexual reproduction in amoeba l.jpg
Asexual Reproduction in unreplicated stateAmoeba


Growth and development l.jpg
Growth and development unreplicated state

1-celled zygote

(2n)

mitosis

Sand dollar embryo

Multi-cellular adult (2n)


Tissue renewal l.jpg
Tissue renewal unreplicated state

Dividing bone marrow cells give rise to new blood cells


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