1. Cellular Reproduction
Ch 11

2. Cell Cycle
Cells reproduce by growing and dividing during the cell cycle
The cell’s DNA is copied in preparation for division to ensure that the two new cells each have an exact copy of the DNA
Cells of all multicellular organisms use this process, and therefore one generation of cells is linked to the next, allowing for the continuity of life

3. Cell Cycle Cell division prevents the cell from becoming too large.
Cells have an optimal size, if it’s too large, it will have difficulty supplying nutrients and expelling waste.
Cell division is also how the cell reproduces, replaces other cells, grows, and heals

4. Cell Cycle
Cell Cycle: a series of events from the time a cell forms until its cytoplasm divides
Multiplication by division
3 Main Stages:
Interphase, Mitosis, Cytokinesis

5. Cell Cycle
A typical cell spends most of its life in interphase, in which it roughly doubles the number of its cytoplasmic components, and replicates its DNA
Three stages of interphase
G1[metabolic activities]: cell is growing, carrying out normal cell functions, and preparing to replicate DNA. Occurs immediately after the cell divides.
S [DNA synthesis]: cell copies DNA in preparation for cell division.
G2 [protein synthesis]: cell prepares for division of its nucleus.

6. Cell Cycle
Mitosis: Process that divides the nucleus of one cell into two nuclei
Mitosis produces two descendant [daughter] cells, each with the same number and type of chromosomes as the parent – IDENTICAL COPIES!
Mitosis MAINTAINS the chromosome number

7. Cell Cycle
Homologous Chromosomes: chromosome pairs of the same length, same centromere position, and control the same inherited trait
At the start of interphase, chromosomes are unduplicated, by the end of G2, each chromosome has two double- stranded DNA molecules [sister chromatids]

8. Cell Cycle During mitosis, the sister chromatids are pulled apart
Each sister chromatid ends up in separate nuclei that are packaged into separate cells

9. Cell Cycle
Whether or not a cell divides is determined by mechanisms of gene expression control
“Brakes” on the cell cycle normally keep the vast majority of cells in G1
“Checkpoint genes” monitor the completion of DNA copying, DNA damage, and nutrient availability
Before mitosis the chromosomes are loosened to allow transcription and DNA replication during interphase, during mitosis the cell grows during various phases

10. Spindle Fibers
Most animal cells have a structure called a centrosome – a region of dense cytoplasm that contains a pair of centrioles
These are copied during prophase, and a copy moves to each side of the cell
Microtubules begin to assemble and form a spindle, which is a temporary structure that moves chromosomes during nuclear division
What would happen if a cell had faulty spindles?

12. Mitosis Prophase Chromosomes condense
Centrosomes move to the opposite end of cell and microtubules begin to assemble and lengthen, forming a spindle
Nuclear envelope breaks up
Sister chromatids are attached to opposite centrosomes

14. Mitosis Metaphase Anaphase Telophase
chromosomes are aligned midway between spindle poles
Ensures there are accurate copies of the chromosomes
Anaphase
sister chromatids separate and move toward opposite spindle poles
Telophase
chromosomes arrive at opposite spindle poles and decondense; two new nuclei form

16. Cytokinesis Cytokinesis: division of cytoplasm
In most eukaryotes, cytokinesis occurs between late anaphase and the end of telophase
The process of cytokinesis differs between plant and animal cells

17. Cytokinesis
Typical animal cells pinch themselves in two after nuclear division ends
Cleavage furrow (indentation) forms
Dividing plant cells face a challenge because a cell wall surrounds their plasma membrane
Disk-shaped structure called the cell plate forms and eventually partitions the cytoplasm
The cell plate forms into two new cell walls

18. I Pray More At The Church!
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
I Pray More At The Church!

19. Cancer
In a normal cell cycle, different cyclin/CDK (proteins) combinations signal activities throughout the cycle
Mutations in these checkpoints can cause a loss of function, and if enough checkpoints fail, a cell loses control over its cell cycle
Interphase may be skipped – division occurs over and over with no resting period
Signaling mechanisms that cause abnormal cells to die may stop working

21. Cancer Tumor: accumulation of abnormally dividing cells
Cancer: disease that occurs when there is uncontrolled division and growth of cells
Malignant cells enter the bloodstream and spread to other parts of the body
Lifestyle choices can reduce one’s risk of acquiring mutations
Do not smoke, avoid sun exposure

22. Telomeres
Telomeres: noncoding repeat DNA sequences (repeated thousands of times) found at the ends of eukaryotic chromosomes
provide a buffer against the loss of more valuable internal DNA
Telomeres shorten with every cell division and when they are too short, checkpoints halt the cell cycle and cell death soon follows
Keeps “uncontrolled” cells from overrunning the body

23. Stem Cells
Stem cells are able to reproduce indefinitely and continuously produce enzymes called telomerases
These reverse telomere shortening that occurs after DNA replication
Embryonic Stem Cells: After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells.
These cells are not specialized

24. Stem Cells
Adult Stem Cells: Found in various tissues in the body and might be used to maintain and repair the same kind of tissue. When these mutate cancer occurs.
Less controversial because the adult stem cells can be obtained with the consent of their donor
Induced pluripotent stem cells: Man-made stem cells. These are created using any cell from an organism.
In humans, a persons skin cell is removed and exposed to chemicals that turn them back into embryonic stem cells.

25. Differentiation
Though our many body cells are different from one another, they are all descended from a single cell
The DNA in our cells contains all the instructions to build an organism, but different genes are active in different types of cells,
This determines the cell’s form and function (differentiation)

26. Cell Death Apoptosis: Programmed cell death
Cells going through this apoptosis actually shrink and shrivel in a controlled process

27. Henrietta’s Immortal Cells
Finding human cells that grow in a laboratory took scientists nearly 30 years to find
In 1951, an assistant prepared a cell line that divided vigorously
These cells were named HeLa cells, after Henrietta Lacks, the patient from whom the cells were taken
Although Henrietta passed away from cervical cancer, her cells live on and are still used today in laboratories all over the world to study cancer and numerous other cellular processes
HeLa cells contributed to the work of Nobel Prize winners