Mitosis And Meiosis Flashcards
How is DNA organised in chromosomes
In humans 22 different autosomes and 2 sex chromosomes x and y
Kinetochores
A protein complex assembled at each centromere
Serves as the attachment site for spindle micro tubules
Micro tubules
Micro tubules are part of the cytoskeleton
It is responsible for various kinds of movements in eukaryotic cells
Involved in cell division as they are forming mitotic spindle
Centrioles
Every animal cell has two small organelles called centrioles
Centrioles consists of a cylindrical array of 9 micro tubules
What is the main differences between mitosis and meiosis
Mitosis: division of somatic body cells
Meiosis: division of gametes sex cells
Mitosis occurs wherever more cells are needed producing two new cells identical to each other (diploid cells)
Meiosis produces haploid cells (egg cells, sperm cells)
What are 5 examples of mitotic cells
- bone marrow
- hair follicle cells
- fibroblast
- hepatic stellate cells liver
- stem cells
Stages of the cell cycle
- prophase
- metaphase
- anaphase
- telophase
What is meiosis
Produces 4 daughter cells
Each daughter cell has half the chromosomes of the parent
Why do we need meiosis
To reduce the chromosomes number in the gamete to 23
To ensure that every gamete is genetically unique
Recombination and diversity
Genetic diversity is important for the evolution of population and species
Meiosis scrambles the specific form of each gene this make a lot of genetic diversity e.g independent assortment and crossing over
Meiosis 1 - prophase 1 Crossing over
During this phase exchange of parts of chromatids follows chromosome pairing (crossing over)
Meiosis 2 telophase 2 and cytokinesis
Nuclei form at opposite poles of the cell
And cytokinesis occurs after completion of cytokinesis there are four daughter cells
Errors during meiosis
Region of homologo exist on different chromosomes
If are is long enough and similar enough recombination can begin causes chromosomes abnormalities or deletions
