ch 8 - growth & the means to sexual reproduction
TRANSCRIPT
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