1. Cell growth and division

2. The cell cycle

3. The cell cycle has four main stages.
Cell cycle: regular pattern of growth, DNA duplication, and cell division in eukaryotic cells.
Phases
Gap 1 (G1): Cell carries out normal functions, grows larger, organelle numbers increase, most time spent here, must pass it’s checkpoint to continue division
Synthesis (S): “the combining of parts to make a whole”, copies it’s DNA, by the end the cell contains two sets of DNA
Gap 2 (G2): continues to carry out normal function, continues to grow, must pass more checkpoints
Mitosis (M):
Mitosis: division of cell nucleus and contents, nuclear membrane dissolves, duplicated DNA condenses and separates, two new nuclei form
Cytokinesis: divides cell cytoplasm resulting in two identical daughter cells

4. https://www. storyjumper. com/coverimg/26104668/The-Cell-Cycle

5. Check for understanding!
What might happen if the G2 checkpoint stopped working in cells?
Cells may be the wrong size, have damaged DNA, and fail to divide.

6. Cells divide at different rates.
Prokaryotic cells divide faster than eukaryotic cells because they do not have membrane- bound organelles and cytoskeleton.
The rate of division is linked to the bodies need for the cells.
G0 phase: cells that divide rarely are in this phase and unlikely to divide.

7. Check for understanding!
Do you think a skin cell would have a long or short G1 stage? Why?
A skin cell would probably have a short G1. Skin cells undergo a lot of wear and tear because they are exposed on the outside of the body. Therefore, they are probably replaced quickly.

8. Cell size is limited.
Size is limited by the ratio of cell surface area to volume. If they are too large molecules could not be transported in and out with adequate speed.
Growth and division must be coordinated to maintain suitable cell size.

9. Check for understanding!
Which has the larger ratio of surface area to volume, a tennis ball or a soccer ball? Explain.
A tennis ball, because the volume increases more rapidly than does surface area as the ball gets larger.

10. Mitosis and cytokinesis

11. Chromosomes condense at the start of mitosis.
Chromosome: long, continuous thread of DNA consisting of genes and regulatory information, our bodies have 46 chromosomes.
Organization allows for function:
During interphase DNA is loosely organized so proteins can access specific genes to copy the seqeence
During mitosis chromosomes are tightly condensed to be divided between two cells
Histones: proteins that DNA wraps around
Chromatin: histones interacting with each other to compact the DNA
Chromatid: half of a duplicated chromosome, sister chromatids are held together by a centromere
Telomeres: ends of DNA molecules that do not form genes but keep chromosomes from attaching to each other and prevent loss of genes.

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13. Check for understanding!
What is the relationship between a molecule of DNA and a chromosome?
A chromosome is made of one continuous DNA molecule.

14. Mitosis and cytokinesis produce two genetically identical daughter cells.
Interphase
Provides time for duplication of organelles and DNA replication
At the end, individual cells have two full sets of DNA and is large enough to divide
Mitosis
Prophase: chromatin condenses into chromosomes, nuclear envelope breaks down, nucleolus disappears, spindle fibers radiate toward center of cell, centrosomes and centrioles move to opposite ends of the cell
Metaphase: spindle fibers attach to centromeres and chromosomes are aligned in the center of the cell
Anaphase: sister chromatids separate and are pulled to opposite ends of the cell
Telophase: identical chromosomes are at each cell pole, nuclear membranes form, chromosomes uncoil, spindle fibers fall apart.

15. Divides cytoplasm for two cells Completes one stage of the cell cycle
Cytokinesis
Divides cytoplasm for two cells
Completes one stage of the cell cycle
Animals: a furrow forms between cells that pinches them apart
Plants: cell plate forms

16. Check for understanding!
How does cytokinesis differ in animal and plant cells?
In animal cells, the membrane pinches together to separate the cytoplasm. In plant cells, a cell plate forms and divides the cell, along which the cell membrane and cell wall re-form.

17. Regulation of the cell cycle.

18. Internal and external factors regulate cell division.
External factors: chemical and physical signals
Growth factors: proteins that stimulate cell division by binding to receptors that activate specific genes to trigger cell growth
Internal factors: triggered by external factors
Kinases: enzyme that transfers phosphate from molecule to another specific molecule to increase energy or change shape of the target molecule
Cyclins: activate kinases, proteins that are quickly made and destroyed
Apoptosis: programmed cell death
Occurs when internal or external signals activate genes that produce self-destructive enzymes

19. Check for understanding!
Suppose a child was born with growth hormone receptors that did not work properly. How do you think this would affect the child’s development?
The child’s ability to produce new cells and, therefore, tissues at the proper rate would be affected. This in turn would affect developing tissues and organs, and also could affect height and weight.

20. Cell division is uncontrolled in cancer.
Cancer: disease characterized by uncontrolled cell division and occurs when regulation of the cell cycle breaks down.
Benign tumor: cancer cells are clumped together, generally harmless
Malignant tumor: some cells break away (metastasize) from the tumor and can be carried through the body
Cancer cells from mutation of normal cells, these mutations can be found in
Oncogenes: accelerate cell cycle
The other stops the cell cycle
Carcinogens: substances known to produce or promote cancer development
HeLa cells are used for cancer research, from cervical tumor removed from Henrietta Lacks

21. Check for understanding!
HeLa cells are also used to study cell signaling processes. What might be a disadvantage of using cancer cells to study processes occurring in healthy cells?
Cancer cells are mutants and may not have exactly the same processes as healthy cells. This could lead to errors.

22. Asexual reproduction.

23. Binary fission is similar in function to mitosis.
Asexual reproduction: creation of offspring from a single parent that does not involve joining of gametes (sexual reproduction), offspring are genetically identical to each other and the parent.
Binary fission: reproduction of a single-celled organism by division into two equal parts
Begins with chromosome being copied
Both chromosomes are attached to a cell membrane
Chromosomes move away from each other as the cell grows
Cytokinesis occurs and a new cell wall forms, creating two new daughter cells
Disadvantage: no genetic diversity

24. Check for understanding!
How is asexual reproduction an advantage in some conditions?
Asexual reproduction results in genetically identical offspring that are well suited to an unchanging environment.

25. Some eukaryotes reproduce through mitosis.
Asexual
Budding: small projections grow on surface of parent organism, forming a separate new individual
Fragmentation: parent organism splits into pieces that can grow into a new organism
Vegetative production: modification of a stem or underground structure of the parent
Some organisms can reproduce sexually and asexually.

26. Check for understanding!
How might the asexual reproduction of genetically identical plants be useful to humans? How could it prove harmful to our food supply?
Since asexually reproduced plants are clones, we can theoretically grow a particular plant in abundance under certain conditions. However, if conditions change, a significant portion of our food supply could be adversely affected.

27. Multicellular life.

28. Specialized cells perform specific functions.
Cell differentiation: process where unspecialized cells develop into their mature forms and functions.
The cells location in the embryo determines differentiation
The cells may then differentiate based on location

29. Check for understanding!
Why is regulation of the differentiation process during the early stages of development so critical?
The early stages of differentiation lead to the development of progressively more specialized tissues and organs. Disruption of cell differentiation in the early stages could cause severe abnormalities in an organism’s body structure.

30. Stem cells can develop into different cell types.
Stem cells: unique cells that can:
Divide and renew themselves for long periods of time
Remain undifferentiated in form
Develop into a variety of specialized cells types.
When they divide they can form two new stem cells or one new stem cell and one specialized cell.
3 Types:
Totipotent: grow into any other cell type, only the first few divisions
Pluripotent: grow into any cell type except totipotent
Multipotent: grow only into cells of closely related cell family
Named based on origin.

31. Check for understanding!
List treatment benefits and risks of both types of stem cells.
Adult stem cells taken the a patient’s own body are less likely to be rejected than those from a donor. However, they can be difficult to isolate and grow, and have limited potential as far as what tissue can develop. Embryonic stem cells can develop into almost any cell type. However, they may be rejected by a patient’s body.