All cells arise from other cells Flashcards
What are the stages of the cell cycle in eukaryotic cells?
interphase, mitosis & cytokinesis
What happens during interphase?
G1/G2 - no. of organelles & volume of cytoplasm increases
S phase - DNA replicates leading to 2 chromatids
What happens during mitosis?
nucleus divides to produce 2 nuclei with identical copies of DNA
What happens during cytokinesis?
cytoplasm & cell membrane divides to form 2 genetically identical daughter cells
What are the 4 stages of mitosis?
prophase, metaphase, anaphase & telophase
What happens during prophase?
- chromosomes condense by becoming shorter & thicker making them visible (chromatids)
- nuclear envelope breaks down
- centrioles move to opposite poles forming spindle network
What happens during metaphase?
- spindle fibres attach to centromere which holds chromatids together
- chromosomes are pulled to equator of the cell
What happens during anaphase?
- spindle fibres contract
- centromere divides pulling chromatids to opposite poles of the cell
What happens during telophase?
- chromosomes uncoil becoming longer & thinner
- nuclear envelope reforms
- spindle fibres & centrioles break down
- 2 nuclei formed
Why do some eukaryotic cells not undergo the cell cycle?
eukaryotes like neurons don’t have spindle fibres therefore can’t divide
What is the importance of mitosis in an organism?
- growth of multicellular organisms by increasing no. of cells
- replacing damaged or worn out cells
- asexual reproduction
How do tumors & cancers form?
- mutations in DNA/genes that control mitosis can lead to uncontrollable cell division
- tumors form if uncontrollable cell division results in a mass of abnormal cells
What are the 2 types of tumors and how do they differ?
malignant - cancerous & can spread (metastasis)
benign - non-cancerous
What is one way cancer treatments control the rate of cell division?
some disrupt spindle fibre activity/ formation so chromatids can’t be separated to opposite poles - this prevents/slows mitosis
What is another way cancer treatments control the rate of cell division?
some prevent DNA replication during interphase so chromosomes can’t make copies which also prevents/slows mitosis
How do prokaryotic cells replicate?
through binary fission:
1. Replication of circular DNA (and plasmids)
2. Division of cytoplasm to produce 2 daughter cells each with a single copy of circular DNA (and variable number of copies of plasmids)
How do viruses replicate?
since viruses are non-living particles they don’t undergo cell division
1. Attachment proteins attach to complementary receptors on host cell
2. Injects viral nucleic acid into cell
3. Infected host cell replicates virus particles: nucleic acid is replicated, cell produces viral protein/capsid/enzymes & virus assembled then released
