the cell cycle. the cycle of life multicellular you mitosis meiosis unicellular you unicellular...
TRANSCRIPT
THE CELL CYCLE
THE CYCLE OF LIFE
Multicellular
You
Mitosis Meiosis
Unicellular You Unicellular Offspring
Cells must be smallAs cells grow bigger, problems developDNA Overload
Same amount of DNA must serve larger and larger areas
Surface Area/Volume RatioCytoplasm increases faster than cell membrane
Cell can’t exchange enough materialMaterial can’t reach center fast enough
WHY MUST CELLS DIVIDE?
SURFACE AREA/ VOLUME RATIOS
Surface Area (cube) = 6 x width2
Volume (cube) = width3
Surface Area/ Volume
COMPARING ORGANISMS
Unicellular Single cell will go through
cycle When cell gets too large,
it will divide Produces two new cell,
each one is its own organism
Form of asexual reproduction called binary fission
Each “offspring” is identical to the parent cell
Multicellular Beginning Cell- Zygote Cell(s) go through cell
cycle to form parts of organism
Cell division continues through development, growth, repair, and wear and tear
Each division creates 2 new cells identical to the parent cell
In some species, can be used for asexual reproduction such as budding and fragmentation
DNA REVIEW
Chromatin- Form of DNA during interphase
Chromosome Form of DNA during cell division
Centromere center point holding two sister chromatids together
Sister chromatids two copies of a chromosome held together by a centromere
Diploid (2n)Cells have 2 sets of chromosomes one inherited from mom and one
from dad
Found in somatic cells (all cells except sex cells)
Different number in different organisms Humans diploid # is 46
Homologous chromosomes- name of the 2 alike chromosomes from each set
DIPLOID
Haploid (n)Cells have 1 set of chromosomes
Found in gametes (sex cells)
Diploid # / 2 Human # is 23 (46 / 2)
When fertilization occurs, the organisms will have the diploid number again
HAPLOID
All cells in a multicellular organism except sex cellsBeginning cell- zygote (fertilized egg)
Totipotent- able to divide and create all the cell types needed in the body
Starts dividing to form early embryo (at 5 days is called a blastocyst) Pluripotent- able to divide and create many of the cell types
needed in the bodyContinues to divide to form the all the structuresAdult stem cells- found in various parts of the body
Multipotent- able to divide and create some of the cell types needed in the body
SOMATIC CELLS
Also called cell differentiation
Many different cell types Each has identical copies of DNA
Each type has a unique shape and function
CELL SPECIALIZATION
THE CELL CYCLE
INTERPHASE
INTERPHASE
Gap phase
Cell grows and carries out normal functions
G1
S PHASE
Gap phase
Cell grows and carries out normal functions
Other organelles replicate
G2
Some cells will never leave interphase or will stay in interphase for a very long time
Phase looks like G1These cells will not divide
G0
CELL DIVISION
Division of the nucleus of somatic cellsOne division with 4 phasesCell divides into two identical daughter cellsCells start diploid and end diploid
MITOSIS
PROPHASE
PROMETAPHASE
METAPHASE
ANAPHASE
TELOPHASE
CYTOKINESIS
ANIMAL VS PLANT CYTOKINESIS
AnimalCell membrane pinches together to form two cells
PlantCell plate forms Will become cell wall to form two new cells
External ControlsGrowth Factors and Hormones- stimulate cell division
Crowding- inhibits cell divisionInternal Controls
Cyclins- proteins whose levels rise and fall during the cell cycle; must reach a certain amount and interact with kinases to create cell division
Checkpoints- check that cell cycle is proceeding correctly S phase- checks if all DNA has been copied correctly Metaphase- checks if all chromosomes are on spindle
fiber
CONTROLLING CELL DIVISION
Uncontrolled cell divisionUsually results from mutations to
Oncogenes- accelerate the cell cycle Genes that stop the cell cycle
p53 gene- normally stops cell division from occurring until all chromosomes are replicated
Cells are undifferentiated and don’t do their job
Benign tumors- stay clustered togetherMalignant spread into other area creating problems (metastisize)
CANCER
Occurs in Unicellular prokaryotes Unicellular eukaryotes Some multicellular eukaryotes
Done by mitosis or processes similar to mitosisExamples
Binary fission Budding Fragmentation
ASEXUAL REPRODUCTION
Combines genetic information from two parentsCreates a unique offspringParents create gametes (sex cells) using meiosis
In humans, egg and sperm
SEXUAL REPRODUCTION
MEIOSIS
Meiosis Occurs in games (sex cells) 2 divisions with 4 phases each (8 phases total) creating 4 unique
cells Cells start out diploid and end haploid
CHARACTERISTICS
PROPHASE I
PROMETAPHASE I
METAPHASE I
ANAPHASE I
TELOPHASE I
CYTOKINESIS I
Similar to mitosisTwo haploid cells created by Meiosis I both divideCreates four haploid cells
MEIOSIS II
Formation of spermStarts at pubertyForms 4 sperm during each meiosisMen will make 5 to 200 million sperm/day
SPERMATOGENESIS
Formation of the eggMeiosis starts inside the womb,
continues is some during every cycle after puberty
1 egg and 3 polar bodies created after every meiosis
Egg must contain lots of cytoplasm to support the developing embryo after fertilization
OOGENESIS