Chapter 2 biology Flashcards
What does diploid and haploid mean? Which type of cells are considered diploid and haploid?
Autosomal cells are diploid: which means that they contain 2 copies of each chromosome.
Germ cells (gamete cells) are haploid: which means that it only contains one copy of each chromosome.
What is meant by the Cell Cycle?
A series of phases during which an eukaryotic cell grows, synthesis DNA, and divides.
What can the dearrangment of the cell cycle leads to?
It can lead to unchecked cell division, which can result in the formation of cancer.
For actively dividing cells, what are the four stages of cell cycle?
G1
S
G2
M
What is the interphase phase? Describe its durination during the cell cycle?
The first three stages (G1,S,G2) are collectively known as interphase.
Interphase is considered the longest part of the cell cycle, where actively dividing cells spend about 90% of their time in interphase.
What is the G0 stage?
Cells that do not divide speed all their time in an offshoot stage of G1, known as G0; where the cell is simply living and carrying out its function but without preparation for division.
What is form of Chromatin in chromsome? why should the chromosome stay in that form?
During interphase, individual chromosomes can’t be seen under light microscope because they are in a less condensed form known as chromatin.
This is because the DNA must be available to RNA polymerase so that the genes can be transcribed (and then translated) into proteins.
–During mitosis (specifically prophase) it is preferable to condense the DNA into tightly coiled chromsomes to avoid losing any genetic material during cell division.
What is another name for the G1 stage? What happens during that stage?
Pre-synaptic gap
Cell duplicate its organelles for energy and protein production (mitochondria, ribosomes, and endoplasmic reticulum) + increase in size.
After completion of G1 stage, what must the cell passes through?
In order to pass into the S stage, the cell is governed by a checkpoint known as therestriction point, where certain criteria (such as containing the proper complement of DNA) must be met in order for the cell to pass the restriction point and enter the synthesis stage (S stage). .
What is another name for the S stage? What happens during that stage (include chromatids, centromere, and the ploidy of the cell)?
Synthesis of DNA
During S stage, the cell replicates its genetic material so that each daughter cell will have identical copies (after mitosis is done), where each chromosome consists of two identical chromatids (the father/mother chomosome + identical chromatid) bound togher at a specialized region known as the centromere.
Note that the ploidy of the cell does not change even though the number of chromatids has doubled. Meaning that the cell in this stage have 46 chromatids, even though 92 chromatids are present (basically b/c this cell has entered the division cycle and it will turn into two daughter cells with 42 chromosomes each). This means that cells entering G2 have twice the amount of DNA as cells still in G1.
What is another name for G2 stage? what happens during that stage?
Post-synaptic gap
Further cell growth and replication of organelles in preparation to enter mitosis + another quality checkpoint to check that: 1) there are enough organelles and cytoplasm for the two daughter cells 2) to check that the DNA replication proceeded without error to avoid passing on an error to the daughter cells and so on.
What are the four phases of M stage ?
Mitosis ( prophase, metaphase, anaphase, telophase) + cytokinesis.
The cell cycle is controled by two checkpoints, what are they?
1st checkpoint between G1 and S.
2nd checkpoint between G2 and M.
What is checked at the G1/S checkpoint and what protein is in main control of this checkpoint?
As mentioned earlier, this checkpoint is also known as the restriction point. During this checkpoint, the cell determines if the condition of the DNA is good enough for synthesis and if the DNA is damaged, then the cell cycle goes into arrest until the DNA is repaired. This checkpoint is controlled by the p53 protein.
What is checked at the S/G2 checkpoint and what protein is in main control of this checkpoint?
During this checkpoint, the cell is ensure that the cell achieved adequate size and the oragnelles have been replicated correctly to support the two new daughter cells. This checkpoint is also controlled by the p53 protein.
What is cyclins and cyclin-dependent kinases (CDK)? How do they become actived? How do they form CDK-cyclin complex?
Both of these molecules are responsible for driving the cell cycle phases (do not get confused with the p53 protein, which is responsible for the 2 checkpoints only).
In order to be actived, CDK require the presence of the right type of cyclins, as the during the cell cycle the concentration of the various cyclins increases and decreases during specific stages. The cyclins bind to CDKs and create an activated CDK-cyclin complex, which can also phosphraylate the transcription factors.
Cell cycle control is essential to ensure that cells that damaged or inadequantly sized do not divide. But what happens when the cell cycle control becomes deranged and damaged cells are allowed to undergo mitosis?
It results in cancerous cells.
How are tumors created?
When cancer cells undergo rapid cell division leading to the creation of tumors.
If the cell begins to produce right factors (such as proteases that can digest the basement membranes or factors that encourage blood vessel formation), then the damaged cells are then able to reach other tissues. What does metastasis mean?
Both local invasion and distant spread of cancerous cells throughout the bloodstream or lymphatic systems. This senario is called metastasis.
What is a common mutation related to cancer?
Mutation of the gene that produces the P53 protein, known as the TP53.
When that gene is mutated it produces malfunctioned p53 proteins and the cell cycle is unable to repair damaged DNA during the G1/S phase. Accordingly, this allows mutations to occur and the cancerous cells to keep dividing withough regard to the quality or quantity of the cells produced.
What is end result of the mitosis process? Can occur in which type of cells and not in which type of cells?
2 identical deploid daughter cells created from a single cell.
Can occur in somatic cells and not in gamete cells (IE: any cells that are not involved in sexual reproduction).
What are 4 things that happen during prophase?
1) Condensation of chromatin into chromsomes.
2) Nuclear envelop dissolves.
3) Nucleoli become less distinct and may dissappear completly.
4) Centriole pairs separate and move towards the opposite poles of the cell and form spindle apparatus
