U1L5 Flashcards
What are somatic cells
Non reproductive cells
How many sets of chromosomes do humans have? How many in total?
2
2 x 23 = 46
What are gametes?
Reproductive cells
How many sets of chromosomes do gametes have? How many in total?
1
1x 23 = 23
If a triploid human could survive, each of its somatic cells would have how many chromosomes?
23 x 3 = 69
What is packaged into chromosomes?
DNA
What do chromosomes consist of?
Chromatin
What is Chromatin?
Complex of DNA and protein that condenses during cell division
What is the centromere?
Constriction that can be seen in the duplicated chromosome where sister chromatids are most closely attached
Define the cell cycle
The cell grows during all 3 sub phases of interphase but chromosomes are duplicated only during the S phase
What are the 3 sub phases of interphase?
G1, S and G2
What happens in the G1 phase?
Metabolic activity and growth
What happens in the S phase?
Metabolic activity, growth and DNA synthesis
What happens in the G2 phase?
Metabolic activity, growth and preparation for cell division
Describe the Mitotic phase of the cell cycle
Mitosis and cytokinesis occurs
Mitosis: Distribution of chromosomes into two daughter nuclei
Cytokinesis: Division of cytoplasm, producing two daughter cells. Each daughter cell can start a new cycle
Describe Bacterial cell division by binary fission
1.Chromosomes replicate and rapidly move to the opposite ends of the cell by a mechanism involving an actin like protein
2. Replication continues and a new copy of the origin is at both ends of cell while the cell elongates
3. Replication finishes, the plasma membrane is pinched inwards by a tubulin like protein and a new cell wall is created
4. Two new daughter cells are made
True or false: Prokaryotes evolved before eukaryotes
True
Where did mitosis evolve from?
Most likely bacteria fission since the mitochondria and chloroplasts divide independently within eukaryotic cells through the use of binary fission
What are the “checkpoints” in a cell cycle and what are they used for?
The cycle has specific checkpoints at which the cycle pauses until a go ahead signal is received. The G1, M and G2 checkpoints are the three that are the most well known
What are the two types of regulatory proteins involved in cell cycle control?
Cyclins and Cyclin-dependent kinases (cdks)
What is a limitation of the cyclin-dependent kinases
Their activity fluctuates during the cell cycle based on the concentration of its cyclin partner which controls cdk activity
What does MPF stand for and its function
Stands for maturation promoting factor is a cyclin- Cdk complex that triggers a cell’s passage past the G2 checkpoint into M phase
Why is the G1 checkpoint the most important?
If a cell receives the go ahead signal at G1 then it usually completes all the other phases and is able to divide
What happens if the cell does not receive the go ahead signal at a checkpoint
Exits the cycle and enters a non dividing state called the G0 phase
Why do some cells not pass the M checkpoint and enter anaphase
Their chromosomes have to be properly attached to spindle microtubules at their kinetochores. A molecular signal is released delaying anaphase until this process happens
What is one factor that can influence cell division and give one example
Growth factors are released by certain cells to stimulate other cells to divide
Ex: Platelet derived growth factor (PDGF) made by platelets stimulate other cells to divide
What is anchorage dependence
In animal cells, to divide they must be attached to a substratum
What is density dependent inhibition
Cells stop dividing once they get too crowded
Describe Cancer cells
Do not respond normally to body’s control mechanisms
May make their own growth factors
Have an abnormal cell cycle control system
How are cancer cells made?
A normal cell is converted to a cancerous cell by a process called transformation. Cancer cells not eliminated by the immune system forms tumour
Differentiate between benign and malignant tumours
Benign: abnormal cells remain only at the original site
Malignant: Invade surrounding tissues
How does metastasis occur?
exporting of cancer cells to other
parts of the body, where they may form additional tumours
What are 5 steps of mitosis
Prophase and pro-metaphase, metaphase, anaphase, telophase , cytokinesis
What happens in prophase?
Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at the centromere.
The nuclear envelope begins to break down.
The mitotic spindle starts to form from the centrosomes, which move to opposite poles of the cell.
What happens in pro metaphase
The nuclear envelope completely disintegrates and chromosomes begin to move toward the cell’s equator
What happens in metaphase
Chromosomes align along the metaphase plate and Spindle fibres are fully formed and attached to each sister chromatid.
What happens in Anaphase
Sister chromatids are pulled apart by the spindle fibers toward opposite poles of the cell.
The centromeres split, allowing the chromatids to separate and become individual chromosomes.
What happens in telophase
Chromosomes reach the poles and begin to de-condense back into chromatin
What happens in cytokinesis
The cytoplasm divides, forming two separate daughter cells
