Ch 8 - Growth & the Means to Ch 8 - Growth & the Means to

sexual reproductionsexual reproduction

Why do cells divide?Why do cells divide?

Replacement of skin cellsReplacement of skin cells

Deadcells

Figure 8.11B

Dividingcells

Epidermis, the outer layer of the skin

Dermis

Figure 8.3A

Asexual reproduction of a prokaryotic cellAsexual reproduction of a prokaryotic cell

Plasmamembrane

Cell wall

Division intotwo cells

Mitosis = asexual reproductionMitosis = asexual reproduction

What do all cells need to What do all cells need to function?function?

DNADNA ))

genomegenome

Sum of genetic information Sum of genetic information Made of autosomes and sex Made of autosomes and sex

chromosomeschromosomes Chromosomes occur in Chromosomes occur in homologous homologous

pairspairs in sexually reproducing in sexually reproducing organismsorganisms

Chromosome number of an organism Chromosome number of an organism can be can be DIDIploid or ploid or HAPHAPloidloid

Karyotype – array of Karyotype – array of chromosomes an organism haschromosomes an organism has

Cell CycleCell Cycle

The cell division party!!The cell division party!!

InterphaseInterphase

G1G1 SS G2G2 G0G0

End results of MitosisEnd results of Mitosis

1 cell has become 21 cell has become 2New cells madeNew cells madeGenetic information has stayed Genetic information has stayed

the samethe sameNumber of chromosomes has Number of chromosomes has

stayed the same in each new cellstayed the same in each new cell

Regulation of Mitosis/growthRegulation of Mitosis/growth Cell checkpoints and feedback Cell checkpoints and feedback

mechanismsmechanisms Growth hormonesGrowth hormones Density dependenceDensity dependence

Growth factors tell the cell to divideGrowth factors tell the cell to divide

Growth factor

Figure 8.8B

Plasma membrane

Receptorprotein

Signal transduction pathway

Relayproteins

Cells continue dividing until they touch one Cells continue dividing until they touch one anotheranother This is called density-dependent inhibitionThis is called density-dependent inhibition

Cells anchor to dish surface and divide.

Figure 8.8A

When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).

If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

Cancer Cancer Cells Behaving Cells Behaving

BadlyBadly unlimited unlimited

division, no division, no apoptosisapoptosis

Feedback signals Feedback signals not workingnot working Benign vs. Benign vs.

malignantmalignant MetastasizeMetastasize tumortumor

• Malignant tumors can invade other tissues and may kill the organism

Tumor

Figure 8.10

Glandulartissue

1 2 3A tumor grows from a single cancer cell.

Cancer cells invade neighboring tissue.

Lymphvessels

Cancer cells spread through lymph and blood vessels to other parts of the body.

Metastasis

Formation of Sex CellsFormation of Sex Cells

Must have haploid number of Must have haploid number of chromosomes in gameteschromosomes in gametes

Reduction/DivisionReduction/DivisionMust reduce the diploid Must reduce the diploid

number by 1/2number by 1/2This is MeiosisThis is Meiosis

Stages …Stages …

One Interphase and chromosome One Interphase and chromosome doublingdoubling

Meiosis I and Meiosis IIMeiosis I and Meiosis II2 cytokinesis2 cytokinesisEnd result – 4 gametes with ½ End result – 4 gametes with ½

chromosome numberchromosome number

Diploid to haploidDiploid to haploid

At the end of Meiosis I, 2 cells At the end of Meiosis I, 2 cells with ½ the chromosome # (one of with ½ the chromosome # (one of each each homologous pairhomologous pair))

Those chromosomes are still Those chromosomes are still made of made of pairs of chromatidspairs of chromatids which which still need to be pulled apartstill need to be pulled apart

Meiosis IIMeiosis II

Simply, mitosis againSimply, mitosis again

Genetic DiversityGenetic Diversity

Crossing overCrossing over Random line-up on metaphase plateRandom line-up on metaphase plate Independent assortmentIndependent assortment

Union of individual gametes to form zygoteUnion of individual gametes to form zygote

Which cells undergo Mitosis? Which cells undergo Mitosis? Meiosis?Meiosis?

The human The human life cyclelife cycle

Figure 8.13

MEIOSIS FERTILIZATION

Haploid gametes (n = 23)

Egg cell

Sperm cell

Diploidzygote

(2n = 46)Multicellular

diploid adults (2n = 46)

Mitosis anddevelopment

MeiosisMeiosis

Forms spermForms spermSpermatogenesisSpermatogenesis

Forms eggsForms eggsOogenesis Oogenesis

Chromosome ErrorsChromosome Errors

DeletionDeletion

InversionInversion

TranslocationTranslocation

Sticky Sticky cromosomescromosomes