1.6 (Topic 1) Flashcards
State the function of mitosis.
The function of mitosis is to create two daughter cells with genetically identical nuclei as the parent cell
List four processes which involve mitosis
Tissue repair/ replacement
Organismal growth
Asexual production
Development (of embryos)
State the names of the four phases of mitosis
Prophase
Metaphase
Anaphase
Telophase
Draw typical eukaryotic cells as they would appear during the interphase
Nucleus intact
Nucleolus visible
DNA as chromatin
DNA is unreplicated
Draw typical eukaryotic cells as they would appear during the prophase
Nuclear membrane breaking down Nucleolus fading DNA supercoiling into the chromosome Spindle fibers form Centrioles move towards cell poles
Draw typical eukaryotic cells as they would appear during the metaphase
Replicated chromosomes align at the cell equator
Draw typical eukaryotic cells as they would appear during the anaphase
Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell
Draw typical eukaryotic cells as they would appear during the telophase
Nuclear membrane reforming
Nucleolus reforming
DNA recoiling to become chromatin
Spindle fibers degrade
Outline the process of metaphase, inclusive of the role of microtubules and the kinetochore.
- Replicated chromosomes align at the cell equator
- a protein complex called the kinetochore located at the centromere is connected to microtubules (a type of spindle fiber)
Outline the process of anaphase.
Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell
Outline four events that occur during telophase.
Nuclear membrane reforming
Nucleolus reforming
DNA uncoiling to become chromatin
Spindle fibers degrade
Describe the structure of a replicated chromosome, including the centromere and sister chromatids.
- Chromosomes are supercoiled strands of DNA
- Replicated chromosomes mean that there are identical copies of DNA called sister chromatids (formed during DNA replication in S phase) attached to each other at the centromere
Explain why chromosomes must condense during mitosis.
To condense means to make DNA denser, or more tightly packed. DNA condenses during mitosis so that it can more easily be moved to the poles of the cell without getting tangled and/or broken
Define cytokinesis.
Cytokinesis is the division of the cytoplasm of a parent cell into two daughter cells
State the difference between mitosis and cytokinesis.
Mitosis refers to the division of the nucleus (nuclear DNA) whereas cytokinesis is the division of the cytoplasm (and organelles in it).
Contrast cytokinesis in plant and animal cells.
Cytokinesis is different in plant and animals cells because plant cells must create new cell wall between the daughter cells; animal cells do not have to form a cell wall
List examples of metabolic reactions occurring during cell interphase.
The majority of the cell cycle is spent in interphase. During interphase “G1”, the cell is performing its specialized function, which requires extensive protein synthesis. During interphase “S”, DNA replication occurs.
Outline events of G1, S, G2, and G0 phases of interphase.
G1: cell grows and performs its specialized functions
S: the DNA replicates
G2: the cell makes the proteins required for mitosis and cytokinesis
G0: the cell is neither dividing nor preparing to divide
Explain the role of cyclin and cyclin-CDK complexes in controlling the cell cycle.
The cell cycle must be controlled so that cells are only dividing when necessary, not continuously. The cell also needs to time for progession through the cell cycle so that it moves from one phase to the next only when all the steps are complete.
Cyclins are protein molecules whose concentration cycle up and down as the cell progresses through the cell cycle. Cyclins attach to other molecules, cyclin-dependent kinases (CDK) to activate progression through the cell cycle. If there is a low concentration of cyclin, the CDK will not be active and the cell cycle will freeze.
State the role of cyclins D, E, A and B in the cell cycle.
Cyclin D: causes progression of the cell through G1 and into S phase
Cyclin E: causes the cell to prepare for DNA replication
Cyclin A: initiates DNA replication in S phase and prepares the cell for mitosis during G2
Cyclin B: progresses the cell through prophase and metaphase. Must degrade for the cell to begin anaphase
define tumor
a mass of tissue caused by abnormal cell division
define benign
a tumor that lacks the ability to invade other tissues or metastasize
define malignant
a tumor made of cells that can invade other tissues and metastasize
define cancer
a disease caused by a malignant tumor
define mutagen
an agent that changes the genetic material of an organism (physical, chemical, or biological)
define carcinogen
mutagens that lead to the formation of cancer
define oncogenes
a gene that has the potential to cause cancer
Describe why mutagens are not necessarily carcinogens.
A mutagen induces mutations in DNA. If the mutation results in uncontrolled cell division and cancer, then the mutagen is also a carcinogen
Describe how cancer arises, referring to the accumulation of mutations over time.
Cells become cancerous after mutations accumulate in genes that control the cell cycle.
Explain the relationship between oncogenes, tumor suppressor genes, and cancer
Proto-oncogenes are normal genes that code for proteins (cyclins) that cell move through the cell cycle
When proto-oncogenes mutate, they become oncogenes. Oncogenes move the cell through the cell cycle even when it shouldn’t divide
Tumor-suppressor genes are normal genes that code for proteins that stop a cell from dividing when it shouldn’t. When tumor- suppressor gene mutates, the cell will divide even when it shouldn’t
Explain the use of correlations to determine the relationship between two variables (inclusive of positive and negative correlations).
Correlations are used to show how related two variables are to each other. Correlations do not necessarily show causation between variables. Positive correlation (direct) - as X increases, Y increases Negative correlation (indirect) - as X increases, Y decreases
Explain why the existence of a correlation does not necessitate a causal relationship between two variables.
For any two correlated variables, the following relationships are possible:
X causes Y
Y causes X
X and Y are consequences of a common cause, but do not cause each other
X causes Z which causes Y
The correlation between X and Y is a coincidence
Outline the relationships between smoking and cancer.
Epidemiologists noticed a relationship between smoking and rates of lung cancer. Since cancer rates when up as smoking rates went up, epidemiologists concluded that there is a positive (direct) relationship between smoking and lung cancer.
Substantial evidence has now been collected to determine that this is a CAUSAL relationship - smoking can cause the development of cancer.
State the formula for the calculation of a mitotic index.
Mitotic Index = # of cells in mitosis/ total number of cells
Calculate the mitotic index of tissue as seen in a micrograph.
Mitotic Index = # of cells in mitosis (shown in red) / total number of cells
Outline the use of mitotic index calculations in the diagnosis and treatment of cancer.
Diagnosis: the higher the mitotic index relative to a tissue specific standard, the more likely a tissue is cancerous.
Treatment: cancer treatments work by stopping cell division, so if a cancer treatment is working fewer cells will be in mitosis. As a result, the mitotic index will decrease if a treatment is working.
Describe the formation of the cleavage furrow in animal cell cytokinesis.
During cytokinesis in animal cells, a ring of actin filaments forms at the metaphase plate. The ring contracts, forming a cleavage furrow, which divides the cell in two.
Describe the formation of the middle lamella and cell wall in plant cell cytokinesis.
The middle lamella is a layer of pectin (a polysaccharide carbohydrate) which cements the cell walls of two adjoining plant cells together. The Golgi buds vesicles containing pectin. These vesicles move to and align at the cell equator. The vesicles fuse, forming a continuous phospholipid membrane with pectin. “Cell Plate” Additional vesicles bring and secrete cellulose to the cell plate forming the cell wall.
