3.2.2 all cells arise from other cells Flashcards
what is produced by mitosis and what are they used for?
-genetically identical cells unless there is a mutation of DNA
-produced by asexual reproduction so are diploid
-used to replace old/damaged cells, growth and embryonic formation
What is produced through meiosis?
-haploid gametes: sex cells which only contain one set of chromosomes
What are the 2 stages in the cell cycle?
-interphase
-mitosis
What phases are within interphase and what happens in each one?
-1st growth phase: replication of organelles. Can enter cell cycle arrest where replication stops
-s-phase: DNA synthesis
-2nd growth phase
What do cells pass through after each stage in the cell cycle?
-checkpoints
-these are genes which code for proteins which control the cell cycle
what are the 4 stages of mitosis?
-prophase
-metaphase
-anaphase
-telophase
What happens in prophase?
-chromosomes condense and become shorter, fatter and visible
-spindle fibres begin to form
-the nuclear envelope breaks down and the chromosomes are free in the cytoplasm
What happens in metaphase
-chromosomes line up along the equator
-chromosomes attach to spindle fibres by their centromere
What happens in anaphase?
-chromosomes divide at the centromere, separating the sister chromatids
-spindle fibres contract
-chromatids are pulled to opposite sides of the cell
What happens in telophase
-chromatids uncoil and become long and thin known as chromosomes
-a nuclear envelope forms
-cell splits into two in a process called cytokinesis
What happens during cytokinesis
-physical separation of the parent cell into 2 genetically identical daughter cells
-cell membrane/ wall forms
What causes cancer
-mutations in the genes that control cell division causing cells to grow out of control
What will happen if the cancer cells pass through the checkpoints
-they will continue to divide via mitosis
-the cells will layer on top of each other forming a tumour.
-these can can cause blockages or damage to other organs
-they need their own blood supply but often they suffer from low oxygen and the blood supply can’t satisfy the tumours oxygen demand causing necrosis
Malignant tumours
-grow quickly and will invade other tissues
-they will break off and spread around the body causing tumours in other organs (metastasis)
-more likely to become life threatening
Benign tumours
-tumour grows slowly and is kept in one place
-they don’t invade other tissues and start tumours in other areas and organs
-not usually life threatening
how do you calculate mitotic index
Number of cells in mitosis/ total cells
How does chemotherapy work?
-prevents the synthesis of the enzymes needed for DNA replication
-meaning the cell cycle stops before the S-phase
-so cells can’t divide
How does radio therapy work
-damages the DNA meaning the cell won’t pass the checkpoint in the s-phase
-forces the cell to kill itself (apoptosis)
-cells won’t divide
How do cancer drugs work?
-prevents the formation of spindle fibres
-so stops anaphase
-means one cell will have double the amount of DNA and the other will have none
-prevents the cell from functioning or dividing again
What does a virus cell contain?
-capsid
-reverse transcriptase
-genetic information
-lipid envelope
-attachment proteins
How are viruses replicated?
-virus attaches via attachment proteins to specific receptors on cell surface membrane
-capsid is injected into host cell (the capsid contains the genetic material)
-genetic material is incorporated into the host DNA
-protein synthesis makes viral proteins
-these assemble and burst out of cells
How is HIV replicated
-HIV attachment proteins bind to specific receptors on the cell surface membrane on T-helper cells
-Nucleic acid/ RNA enters cell
-the reverse transcriptase turns the RNA into DNA
-protein synthesis makes viral proteins
-these assemble and burst out of cells
How does bacterial replication by binary fission work
-circular DNA and plasmids replicate
-cytoplasm divides
-cell wall reforms
Why do bacteria replicate via binary fission
prokaryotes have no centrioles so no there is no spindle fibres so sister chromatids can’t be separated
