Cell Cycle

Nucleosome

'spooled' unit consisting of DNA and histones proteins; unit of chromatin

What are replicated chromosomes?

1. They consist of 2 sister chromatids 2. Relationship: they're identical copies of each other- Conjoined together 3. Replicated chromosomes are 1 chromosomes until the centromere breaks a. replicated chromosome is made up of sister chromatid b. Centromere breaks and separates 92 chromatids from each other in humans

Diploid

2n chromosomes

What are the differences between animal cell and plant cell mitosis?

Animal: 1. Contains centrioles 2. Cytokinesis is evident earlier 3. Cytoplasm pinches off Plant: 1. Does not contain centrioles 2. Cytokinesis is evident later 3. Chromosomes pulled opposite pole, vesicles start to appear containing primary components of cell wall

Explain why neither cyclins nor kinases alone can cause a cell to progress through the cell cycle.

Because they need each other to do work. Kinase without cyclin is inactive kinase and it cannot do anything to help the cell. So for a kinase to be active, it needs to be bound to the right cyclin. Without a cyclin, kinases are inactive. Once they bound, they take one phosphate from ATP molecules to activate proteins and enzymes.Active kinases can power cell repairing itself if needed after a checkpoint, also powers cell suicide if cant be fixed

What is the role of the centromere in mitosis?

Centromeres are the specialized region of a chromosome that holds sister chromatids together. In mitosis they attach to the spindle.

How do the chromosomes move during mitosis?

Chromosomes are duplicated and condense into a jumbled mess within the nucleus. The sister chromatids are arranged along the metaphase plate, where spindle fibers attach to the sister chromatids. Once the centromere breaks, the spindle fibers shorten by disintegrating at the MTOC, pulling them apart to opposite poles in the cell. The nuclear membrane then reforms around the chromatids and Cytokinesis will then occur.

M Phase

Consists of mitosis and cytokinesis

Sister Chromatids

Copies of 1 homologue joined at centromere

If a mutation arose in a G1 cyclin, causing it to bind a kinase constantly, what would happen to the cell? Explain.

Cyclin permanently bound to kinase, constantly pushing cell through stage in cell cycle cyclin concentrations peak and then rapidly uncontrolled cell division = cancer.

Explain why DNA replication is important in cell division.

DNA replication is important in cell division because DNA is the genetic software, it runs the cell and what goes on. DNA controls the production of enzymes. Without DNA replication the cell does not have the genetic material to create proteins that are needed for the body to function. An error in DNA replication or cell division can lead to birth defects, cancer, or other serious diseases.

What two pathways are disrupted in cancer cells?

Either a mutation or damage done to the genes that speed or slow the cell division (damage the break or accelerator)

Daughter Cells

Either of the two cells formed when a cell undergoes cell division by mitosis. Daughter cells are genetically identical to the parent cell and each other

Describe how errors are corrected in DNA.

Errors in DNA are corrected by the first two checkpoints in both the G1 and G2 phase. Enzymes check if the genetic material has no damage and later if all genetic material is duplicated correctly and if all genetic material is intact.

Cancer Cell

Extremely frequent cell division. Events before division: -Cell swells in mass - Goes through cell cycle fast - Cannot stay in G1 - Always will divide - no regulation. Errors: None

Skin Cell

Frequent Division. Events before division: - Cell grows 1.5- 2x size -DNA replicates -Cyclin increases concentration, which helps the cell grow - Cyclin accumulates slowly Errors: - DNA replication is incomplete - Factors regulating cycle are faulty → leads to cell destruction or cancer

Blood Cell

Frequently divides. Events before division: -grows 1.5- times -Cell grows 1.5- 2x size -DNA replicates -Cyclin increases concentration, which helps the cell grow - Cyclin accumulates slowly Errors: - DNA replication - Cell Death - Cancer

What determines whether a cell stays in interphase or divides?

If a cell passes all of the checkpoints and the restriction point determines this. WHAT PUSHES A CELL PAST THE RESTRICTION POINT? Cell growth/ size, if more cells are needed chemical signals (hormones) will tell the cell to divide.

Liver Cell

Infrequent cell division. Events before division: -grows 1.5- times -Cell grows 1.5- 2x size -DNA replicates -Cyclin increases concentration, which helps the cell grow - Cyclin accumulates slowly Errors: -DNA replication - Cell Death - Cancer

What is mitosis?

It is the process that distributes a copy of each chromosome to each new cell during eukaryotic cell division; division of the nuclear contents of cell; clones nucleus. It's made up of four stages each doing a specific task.

Cyclin-Dependent Kinase (Cdk)

Kinases are enzymes that transfer Phosphate (energized it) from ATP to other enzymes activating target Enzyme, it's only active when bound to appropriate cyclin --When cyclin binds to inactive kinase, activates it --Takes phosphates from atp, energizes inactive enzyme that catalyse a set of reactions that push it further through the cell cycle ----Changes shape of enzyme so it can bind to whatever to energize it (this is what phosphorylating does)

What is the major event in M phase? S phase? G0 phase? G1? G2?

M phase: Series of events that ensures that each new daughter cell receives one copy of each chromosome. Division of nucleus. Whole cell divides. S phase: The DNA of each chromosome replicates to form a new identical set of chromosomes. This doubles the number of genes in the nucleus. DNA replication G0 phase: Stopping point within G1. The cells in the G0 phase are metabolically active and specialized to perform the tasks necessary to sustain the life of the organism, i.e. synthesize RNA, proteins, and other macromolecules . Normal cell growth and metabolism G1 phase: The G1 phase is the primary growth phase where normal growth and metabolism occurs. The restriction point is located here, committing the cell to undergo mitosis. G2 phase: The G2 phase is the secondary growth phase where growth and metabolism are geared towards cell division. The cell is preparing for mitosis and doing what is needed in order to divide

Why is controlling what enters and exits the cell more effective in small cells?

Membrane has role in controlling what enters & leaves cell Control is more effective in small cells because SA>relative volume in small cells. Increase sa = increased diameter ^2 Increased volume = diameter ^3

What is the difference between a cancerous tumor and metastasis?

Metastasis is the process of how a cancerous tumor is created. During metastasis, there are mutated proteins which are able to make it through the cell cycle because there is not any cell regulation or checkpoints. Checkpoints can become inactive if growth signals enter the wrong pathway. A malignant cancerous tumors is the result of metastasis, so it's metastasis. A malignant cancer is a metastatic one.

What is the difference between mitosis and mitotic cell division?

Mitotic Cell division is the process of creating a new cell with the same DNA as the original cell. Mitosis is the process of replicating dividing chromosomes to distribute to each eukaryotic cell. During Mitosis two sister chromatids are synthesized, but during mitotic cell division the whole cell divides- which includes the nucleus, cytoplasm, etc. Mitosis creates these two sister chromatids which have the exact same DNA. Mitotic cell division makes a brand new cell with the exact same DNA as the previous cell. Mitotic cell division includes cytokinesis, while mitosis does not

How does the importance of cell division differ in unicellular and multicellular eukaryotes?

Multicellular organisms usually develop from a single fertilized egg cell, unicellular organisms do not. The many types of cells that make up the organisms' tissues and organs develop through many cycles of division that began with that one fertilised egg cell. Maintenance, repair, growth, production of specialised tissues.

Nerve Cell

No division, thus no events before division, and no errors cell stays in G0.

G1 Phase

Primary growth phase (normal growth and metabolism), cell spends most of its life here, it's' where a cell will enter or leave G0, the restriction point located here

What events characterize the different phases of Mitotic Cell division?

Prophase: the nuclear membrane breaks down into small vesicles, chromosomes condense and can be observed under a light microscope, microtubules form around the nucleus to form a mitotic spindle, spindle poles are formed, and sister chromatids move to separate poles Metaphase: motor proteins (in kinetochores) line up on the metaphase plate (pull chromosomes into a ring between poles), makes sure that each daughter cell gets the same chromosomes. Anaphase: enzymes break down protein connecting sister chromatids, centromere splits due to the shortening of spindle poles, motor proteins move them back to opposite poles, segregated sister chromatids are now considered chromosomes. The spindle fibers are being pulled by the spindle poles around the MTOC Telophase: uncoiling of chromosomes (they become chromatin), re-formation of nuclear envelope forms two nuclei, cytokinesis begins to occur, spindle fibers disintegrate.

What are the similarities (in a blood cell, skin cell, and liver cell) and differences between different cells?

Similarities in Blood cell, Skin cell, liver cell: 1.Cells can grow slowly and stay in G0 2. Cells grow 1.5-2x larger- 3. DNA Replication 4. Cyclin accumulates- Differences in cells: 1. Speed (Regeneration) 2. Frequency of division 3. Growth

What is the difference between chromosomes and sister chromatids in the M phase?

Sister Chromatids have a centromere connecting them and are exact copies of one another with the same DNA while a chromosome is singular. Sister chromatids when connected by the centromere are considered one chromosome, however once the centromere is broken they are each considered their own chromosome.

Briefly describe the major event of mitosis.

Sister chromatids are split apart to opposite poles of the cell. A nuclear membrane is then made around each new nucleus, and then the cell splits into two.

What could trigger cell division?

Size could: A cell may be triggered to divide because of an increase of size. The larger the SA:V ratio, the larger the % of volume diffused. The larger the cell, the smaller the SA:V. A cell is more efficient when smaller (better having 600 loading docks than just 2) When a cell grows larger, the SA:V ratio decreases, making the cell unable to sustain normal functions, thus triggering division. Smaller cells have a larger ratio of SA to V (600:1). That is because: Increase of surface area = increase diameter2 Increase of volume = increase diameter3 Also, hormones (chemical signals), space opening up because of dead cell

What are some factors that might influence the cell cycle? (6 examples)

Some factors that might influence the cell cycle are: 1. If a cell doesn't need to grow larger or replace many of its cells 2. Chemical signals (hormones) 3. Cyclin accumulation 4. Death of nearby cells 5. Damage 6. DNA replication error

What is the role of the spindle in mitosis?

Spindles divide the chromatids during nuclear division and so they are very important in the metaphase and anaphase. Without them the chromatids couldn't move to the metaphase plate or to the spindle poles.

What is the biological importance of the cell cycle? Of S Phase? Of M Phase?

The biological importance of the cell cycle is that without it cells that cannot or are not ready to divide can continue and this would most likely cause problems such as cancer. The importance of S Phase is that in it DNA synthesis occurs and so damaged DNA is repaired. Without this, problems in the DNA could occur. The M phase is important as it's where the cell actually divides, so without this all cells would live in atrophy.

What is the cell cycle?

The cell cycle is a 4 phase process that eukaryotic cells have to follow in order to reproduce. The cycle has several checkpoints and regulations that catch errors and control cell division rate.

Describe the four phases of the life cycle

The four phases of the life cycle (in order) are: the G1 phase, S Phase, G2 Phase and M Phase. 1. The G1 phase is the primary growth phase where normal growth and metabolism occurs. The restriction point is located here, committing the cell to undergo mitosis. 2. If a cell has passed this point it enters the S Phase where DNA replication occurs and the cell has committed to dividing. 3. The G2 phase is the secondary growth phase where growth and metabolism are geared towards cell division. The cell is preparing for mitosis and doing what is needed in order to divide. 4. Finally the M phase is where the cell undergoes mitosis and cytokinesis.

Why would cell growth push a cell past the restriction point?

The larger the SA:V ratio, the larger the % of volume diffused The larger the cell, the smaller the SA:V More efficient when smaller - better having 600 loading docks than just 2 When larger, it will be more problematic getting the waste away, so divides p53 - protein that reads DNA and will initiate repairing

How does the nucleus divide during mitosis?

The nucleus divides by disintegrating in prophase, allowing the chromosomes to separate. During telophase a new nuclear membrane reforms around each group of chromatids.

Interphase

The part of the eukaryotic cell cycle between cell divisions consisting of cell growth and DNA synthesis phases, G1, S, and G2. DNA Replication Stays as loose coils of Chromatin Nuclear Membrane is intact

How do controls on the cell cycle protect multicellular organisms from accumulating large numbers of damaged or defective cells?

There are steps during the cell cycle where they go through checkpoints that make sure everything is going as planned and nothing has happened. But if something does happen, proteins at the checkpoints quickly fix the problem. For them to fix the problem however, they need to stop the cell cycle while they fix the mistake.(cell-cycle arrest). Also, different proteins activate enzymes (they are called p53) that prevent the damaged part from entering the next phase until the damaged part is fixed. If a cell is too badly damaged, apoptosis occurs, triggering the lysosomes to digest the cell and kill it.

Know the phase names of mitosis

They are prophase, metaphase, anaphase, and telophase. (P-MAT)

Know the different phases of the cell cycle

They are the Gap 1 Phase, Synthesis Phase, Gap 2 Phase, and Mitosis Phase, and sometimes Gap 0 phase

Cleavage furrow

This is visible in animal cells once the cytoplasm starts to divide- the cell is being pinched in the center which begins to form the two new daughter cells. (Image a water balloon being pinched in the middle)

What are the functions of tumor-suppressor genes and proto-oncogenes in the noncancerous cells?

Tumor suppressor (break- slows division) genes are genes that inhibit cell division when there is a damaged part of the DNA chain or a mutation. Proto-oncogenes (accelerator- promotes cell division) are genes that promote cell division, in direct and indirect ways.

Describe the phases of Mitosis and compare them with each other

Use chromosomes, all within the M phase and so division of the nucleus, they are all regulated by cyclin/cdk complexes to push them through the cell cycle

When errors occur in DNA, what activity do checkpoint controls inhibit?

When errors occur the checkpoint alerts enzymes to begin cell cycle arrest to repair the damage, but if the error is too bad, apoptosis occurs. The checkpoints check size, correct duplication, spindle fibres attached correctly

S Phase

Where DNA replication occurs, committing to dividing

Cells can be grown in a laboratory by a process called tissue culture. Imagine that you have two tissue cultures, one of them in G1, one of them in the G2 Phase. Unfortunately, the cultures labels have been misplaced, how would you determine which cultures are in G1 and which are in G2?

You can determine which are in G1 and which are in G2 as those in G1 are only in the primary period of growth and those in G2 are in their secondary. Double the amount of nucleic acid (as the amount of DNA has doubled) G2 cyclins vs G1 cyclins.

Restriction point

a point of no return in the cell cycle; once this point passes, a cell is committed to a full round of the cell cycle

Nucleotide

a subunit of DNA or RNA composed of a 5 carbon (pentose) sugar, nitrogen containing base and phosphate group.

Genes

a unit of information for a heritable trait encoded in DNA

Allele

alternate/different forms of a gene (dominant or recessive)

Cell cycle arrest

an abrupt halt in the cell cycle when proteins detect mistakes or damage in DNA that needs to be repaired

Cell cycle

an ordered sequence of events in the life of a dividing eukaryotic cell, composed of mitosis (M) and interphase growth and DNA synthesis (G1, S, G2)

Somatic cells

body cells excluding sex cells, these are diploid

Apoptosis

cell suicide

Polymer

chain of monomers bonded together

Chromosome

condensed chromatin

'n' (in regards to haploid and diploid)

copy of chromosomes

Cell/ Metaphase Plate

during nuclear division, an imaginary plane that is equidistant between the spindles two poles. (a plane that bisects the cell)

Zygote

first cell of new individual: result of fertilisation

Fertilisation

fusion of gametes

G2 Phase

growth/ metabolism geared towards cell division - 2nd growth phase, cell doing what it needs to do in order to divide, prepares for mitosis

Chromatin

in eukaryotes, the chromosomal material (DNA and associated proteins) as it ordinarily appears in a cell's nucleus, with individual chromosomes indistinct. made of nucleosomes

Haploid

n chromosomes

Checkpoint 1

occurs in G1. checks: Cell size, if genetic materials have no damage. restriction point

Checkpoint 2

occurs in G2. occurs in G2. checks that all genetic material duplicated correctly and intact, big enough to continue

Checkpoint 3

occurs in M phase, near the end of the metaphase stage of mitosis. Chromosomes are attached to spindles

G0

occurs when cell pauses in G1 before DNA replication, cells can remain in G0 for days, years or permanently, no longer dividing

Asexual reproduction

one parent produces offspring through mitotic cell division

Homologous chromosomes

paired chromosomes that code for the same traits

Microtubule organising center (MTOC)/ centrosome

polar region of cell where mitotic spindle microtubules form and are assembled around/emanate from - in plant cell it isn't focused while in animals it's focused and on a specific point (around the centrioles). There is an Aster in an animal cell

Binary Fission

prokaryotic cell division

Cyclin

protein that regulates progress through the cell cycle. Accumulate and rapidly disappear, G1 and Mitotic cyclins are most important

Gamete

sex cells Eg. sperm and eggs

Monomer

small repeating unit of macromolecule

Mitotic spindle

structure made up of microtubules and proteins, divides the chromatids during nuclear division

Nuclear division

the division of a cell's nucleus, as in mitosis or meiosis

Cytokinesis

the division of the cytoplasm of a cell after nuclear division. In eukaryotic cells

Telophase

the final stage in mitosis (and meiosis 1 and meiosis 2) characterized by two new nuclei forming at opposite ends of the cell; frequently followed by cytokinesis (cell division) Protein microtubule belt pinches off cytoplasm. Chromosomes uncoil back to chromatin.

Anaphase

the phase in cell division in which 1. chromosomes separate and move toward opposite ends of the cell to the spindle poles by microtubules and they are disassembled @ MTOC Spindle Fibres will also push the poles apart.

Metaphase

the phase in mitosis (and meiosis) in which 1. chromosomes move to the center of the spindle, an array of microtubules connect to centromere on each chromosome (spindle fibers from each pole connect each replicated chromosomes- the centrioles in animals are located in the MTOC region) 2. chromosomes are lined up on the metaphase plate (the equator) 3. the last event: centromere breaks and the sister chromatids separate

Mitosis

the process that distributes a copy of each chromosome to each new cell during eukaryotic cell division; division of the nuclear contents of cell; clones nucleus

Centromere

the specialized region of a chromosome that holds two replicated chromosomal strands together and that attaches to the spindle in mitosis. Narrow point where sister chromatids are joined

Aster

the spindle fibers that emanate from all directions from the MTOC in animal cells

Prophase

the stage of mitosis during which 1. replicated strands of chromosomes condense 2. the nuclear envelope (membrane around the nucleus) disintegrates and is packed into small vesicles 3. the mitotic spindle forms

Metabolism

the sum of all chemical changes taking place in an organism.

Sexual reproduction

two parents contribute to genetic makeup of offspring through fusion of gametes