Unit 2 - Key Area 1 - Producing New Cells Flashcards
What is mitosis and why do cells carry it out?
Mitosis is the division of the nucleus.
Mitosis provides new cells for growth, repair of damaged tissues, and replacement of dead or damaged cells.
It also maintains the diploid chromosome compliment .
Describe the number of chromosomes in different cells
A gamete (sex cell) has half the number of chromosomes as any other cell in that organism. They have one set and are known as haploid.
All other cells have double the number of chromosomes than that of a haploid cell. They have 2 sets are known as diploid.
What is a chromosome compliment?
The number of chromosomes that certain organisms should have is called the chromosome complement.
The chromosomes contain all the genetic information required for the growth and development of that species.
What must happen to chromosomes at the beginning of mitosis?
All the chromosomes in the nucleus replicate their DNA to make identical copies. The nucleus now contains 2 sets of chromosomes, twice as many as a normal body cell.
What is the purpose of mitosis?
Mitosis ensures that the new cells contain the same number and type of chromosomes (the chromosome complement) so the new cells contain all the information for the growth and development of that species.
Describe stage 1 of cells division
Parent cell chromosomes are copied and become visible as sister chromatids. Nuclear membrane disappears.
Describe stage 2 of cell division
Chromatids line up at the equator (middle of the cell)
Describe stage 3 of cell division
Spindle fibres attach to the centromere then contract
Describe stage 4 of cell division
The chromatids are pulled apart to opposite sides of the cell by spindle fibres.
Describe stage 5 of cell division
Chromosomes move to opposite sides of the cell
Describe stage 6 of cell division
Nuclear membrane reforms and the cytoplasm divides.
Two new cells identical to parent cell are made.
What are stem cells?
Stem cells in animals are unspecialised cells which can divide in order to self-renew. They have the potential to become different types of cells (specialisation).
Where can stem cells be found?
Stem cells can be obtained from the embryo at a very early stage. In addition, tissue stem cells can be found in the body throughout life. They are involved in growth and repair.
How are cells organised in a multicellular organ?
Multicellular organisms have more than one cell type and are made up of tissues and organs which perform different functions. The cells in organs are specialised for their function and work together to form systems.
What is cell hierarchy?
Cells -> Tissue -> Organ -> System
