Cell Division Flashcards
What does the cell cycle describe?
The life of a cell
What is the period called where the cell is not dividing?
Interphase
What is the period called when a cell divides?
Mitosis
What is the longest phase in a cell’s life cycle?
Interphase
What % is a cell’s life spent in interphase?
90%
What is the cell like at the beginning of interphase?
The cell is very active, producing new organelles and chemicals needed for growth
What does the cell do at the end of interphase?
The chromosomes make identical copies of themselves- double stranded chromosome
What is the next phase after interphase?
Prophase
What happens in the cell during prophase?
- The chromatin condenses
- Chromosomes become visible as a double stranded structure
- Spindle fibres appear in cytoplasm
- Nucleolus disappears
- Nuclear membrane starts to break down
What is the next phase after prophase?
Metaphase
What occurs in the cell during metaphase?
- Nuclear membrane is broken down
- Chromosomes line up across the centre of the cell
- Spindle fibres from each pole attach to each chromosome at the centromere
What occurs after metaphase?
Anaphase
What occurs in the cell during anaphase?
- Spindle fibres contract- centromere splits
- One chromosome from each double-stranded chromosome is pulled to opposite poles of the cell
- The four chromosomes pulled to each pole have identical sets of genes
What is the next phase after anaphase?
Telophase
What occurs in the cell during telophase?
- The four chromosomes at each pole elongate to form chromatin
- The spindle fibres break down
- Nucleolus re-forms
- Nuclear membrane forms around the chromatin at each pole
What occurs in animal cells to produce new cells?
A cleavage furrow
What occurs in plant cells to produce new cells?
- Small membrane enclosed sacs called vesicles gather in the area between the two nuclei
- These vesicles form the cell plate
- Two cell walls form from the cell plate
What is the function of mitosis in unicellular organisms?
-Method of reproduction for amoeba
What is reproduction without the joining of two cells called?
Asexual reproduction
What is the function of mitosis in multicellular organisms?
- Produces new cells
- Growth and renewal and repair of cells
What is cancer?
Is a group of disorders in which certain cells lose their ability to control both the rate of mitosis and the number of times mitosis takes place.
What are malignant tumours?
Uncontrolled multiplication of abnormal cells
What is movement of these cancer cells called?
Metastasis
What causes cancer?
When normal genes are altered to form cancer-causing genes called oncogenes
Name some cancer causing agents.
Carcinogens- cigarette smoke, asbestos fibres, ultraviolet radiation and some viruses
What is meiosis?
Form of nuclear division in which the daughter nuclei contain half the chromosome number of the parent nucleus
How many chromosomes do human cells have?
46 chromosomes
Where does meiosis occur?
In the ovaries and testes
What is the two functions of meiosis in multicellular organisms?
- Sexual reproduction without increasing number of chromosomes in offspring
- Allows new combinations of genes- variation
