The Cell Cycle Flashcards
What is cell division?
Follows nuclear division, process by which whole cell divides
What are the four requirements needed for semi-conservative replication to take place?
- four types of nucleotide present w/ four bases
- both strands of DNA template for nucleotide attachment
- enzyme DNA polymerase = catalyst
- source of chemical energy
Name the 6 steps of semi-conservative replication of DNA
- DNA helicase enzyme breaks H+ bonds
- Double helix separates into two strands & unwinds
- Each strand acts as template, energy used to attract free nucleotides to join to complementary bases
- Lined up nucleotides joined by DNA polymerase to form missing strand
- Two new molecules of identical DNA, each with ½ original strand
What is nuclear division?
The process by which the nucleus divides, two types: meiosis & mitosis
Explain the conservative model for DNA replication
- one new daughter DNA completely new material
- one daughter DNA completely original material
How is the conservative model different to the semi-conservative?
- semi = half original DNA & half new
- cons = one new one old DNA
What might happen that would result in the daughter cells not being genetically identical to the parent cell after mitosis?
Mutation
Name the 5 stages of mitosis in chronological order
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens in interphase of mitosis?
- cell actively synthesizing proteins
- chromosomes invisible
- DNA replicates
What happens in prophase of mitosis?
- chromosomes become visible
- nuclear envelope dissolves
- nucleolus disappears
- centrioles migrate to opposite poles & produce spindle fibres
What happens in metaphase of mitosis?
- spindle fibres attach to centromeres of chromosomes
- chromosomes line up along equator
What happens in anaphase of mitosis?
- spindle fibres contract
- chromatids pulled to opposite poles (daughter chromosomes)
What happens in telophase of mitosis?
- chromatids become indistinct at opposite poles
- chromosomes no longer visible
- nuclear envelope reforms
- nucleolus reforms
- spindle fibres dissolve
- cytokinesis: cell divides
Explain the 3 reasons why mitosis is so important
- growth: mitosis ensures that offspring look like parents by replicating diploid cell after gametes fuse
- differentiation: specialized cells divide by mitosis to create tissues with specific functions
- repair: mitosis creates new cells to replace damaged/dead ones to retain efficiency
What are the 3 stages of the cell cycle?
- Interphase
- Nuclear division
- Cell division
Name the 3 stages of interphase in the cell cycle
- G1: protein synthesis to make cell organelles
- S phase: DNA replication, each chromosome double stranded
- G2: organelles grow & divide, energy stores increased, checkpoint for damage to DNA before mitosis
What happens in stages 2 & 3 of the cell cycle?
- Nuclear division = nucleus divides into 2 or 4
3. Cell division = whole cell divides into 2 or 4 daughter cells
What is cytokinesis in the cell cycle?
Final stage of cell cycle, triggers beginning of G1 phase
Describe the difference in the number of times a normal body cell divides compared to a cancerous one
Normal body cell = divides enough times to make new cells for repair & growth
Cancer cell = divides uncontrollably
What makes a cell cancerous?
Mutation in the gene that causes cell division (change in base sequence of DNA)
What is cancer?
A tumor that invades surrounding tissue
How do treatments for cancer aim to work?
Target the tumor cells which divide more rapidly than regular body cells
Give two examples of how cancer treatments target the cell cycle
- G1: chemo, stops synthesis of enzymes for DNA replication, cell unable to enter Sphase & suicide
- S phase: radiation/ drugs damage DNA, cell detects damage & suicide preventing further tumor
Why do cancer patients suffer side effects of nausea & hair loss during treatment?
Hair cells & gut lining cells are very rapid dividing cells
Explain two steps taken during cancer treatment to prevent normal cells being killed
- treatments given with short breaks inbetween: allows body to recover & produce new cells but not long enough for cancer to grow back to original size
- some tumor cut off first: increases access to any cancer cells left for nutrients & O2, they enter cell cycle & more susceptible