Cells: All cells arise from other cells Flashcards
Define tumour:
A swelling in an organism made up of cells that continue to divide in an abnormal way.
What type of cell division produces genetically identical cells?
Mitosis
What do the newly produced cells from mitosis replace?
Old/damaged cells
What is a diploid cell?
A cell that has two sets of chromosomes.
What type of cell division produces diploid cells?
Mitosis
What are haploid gametes?
Sex cells that have half the normal amount of chromosomes.
What type of cell division produces haploid gametes?
Meiosis
What are the two main stages that make up the cell cycle?
- Interphase
- Mitosis
What are the three stages that occur in interphase?
- Growth stage 1
-Synthesis of DNA (S-phase)
-Growth stage 2
What happens in stage Growth stage 1 during interphase?
- Replication of organelles, e.g. mitochondria, ribosomes
What happens in synthesis of DNA stage during interphase?
- Replication of DNA (DNA content will double)
What happens in growth stage 2 during interphase?
- Checks that cell is ready for mitosis
In what stage of interphase does cell cycle arrest occur?
G1
What happens in cell cycle arrest?
- Cell cycle stops
- Cell ‘rests’
What are checkpoints in the cell cycle?
Stages where the cell is checked to ensure that it is ready to move on to the next phase of the cell cycle.
What are checkpoints controlled by?
Genes that code for proteins
What is created through mitosis?
Two genetically identical daughter cells
Give three reasons why mitosis is important in the life of an organism:
- Allows the creation of new body cells for growth and repair
- Replaces old/damaged cells
- Embryo formation
Give three reasons why meiosis is important in the life of an organism:
- Haploid gametes are produced, allowing fertilisation
- Genetic variation
- Restoring chromosome number
What are the four stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens in prophase?
- Chromosomes condense, becoming shorter, fatter and visible
- Spindle fibres begin to form
- Nuclear envelope breaks down; chromosomes become free in the cytoplasm
What happens in metaphase?
- Chromosomes line up at the cells equator
- Chromosomes attach to spindle fibres by their centromeres
What happens in anaphase?
- Chromosomes divide at their centromere, separating the pair of sister chromatids.
- Spindle fibres contract, pulling the chromatids to opposite poles of the cell centromere first.
What happens in telophase?
- Chromatids reach the opposite poles of the cell and uncoil, becoming long.
- Nuclear envelope forms around each set of chromosomes
- The cell splits into two (cytokinesis)
What is cytokinesis?
The reforming of the cell membrane/wall and the separation that produces two genetically identical daughter cells.
What is a centriole?
Organelles that produces spindle fibres
What is the role of the centromere in mitosis?
Allows chromosomes to move towards the opposite poles of the cell.
How does chemotherapy work?
- Prevents enzyme synthesis (required for DNA replication)
- S phase will not occur
- DNA cannot be replicated = division cannot occur
How do drugs work to treat cancer?
- Prevent spindle fibres from forming
- One cell will have 2x normal amount of chromosomes, one cell will have none.
- Cells are faulty and cannot divide.
How does radiotherapy work?
- Damages cells DNA.
- Cell will not pass checkpoints in S phase
- Causes apoptosis
What is a carcinogen?
A chemical form of radiation or other agent that causes cancer
What is the centromere?
The centre structure within a chromosome that joins the chromatids.
What is a clone?
A group of genetically identical organisms formed from a single parent by asecual reproduction.
What is differentiation?
The process by which a cell becomes specialised for different functions.
What are homologous chromosomes?
A pair of chromosomes (one maternal, one paternal) that have the same gene loci and determine the same features.
What is a mutagen?
Any agent that induces a mutation
What is a mutation?
A sudden change in the amount or arrangement of the genetic material in a cell
What is a photomicrograph?
A photograph of an image produced by a microscope
What are stem cells?
Undifferentiated dividing cells that occur in embryos and adult animal tissues that require constant replacement.
What is the tumour suppressor gene?
A gene that maintains normal rates of cell division and prevents the development of tumours.
Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of this:
More cells can be produced to replace damaged/old cells.
