Mitosis and meiosis Flashcards
What is mitosis
Cell division that produces two daughter cells genetically identical to the parent cell.
What is the purpose of mitosis
Growth and repair
Where does mitosis occur
In all stem cells/mother cells
e.g. skin, bone, blood, muscle
How does mitosis occur
starts with one body cell with 46 chromosomes
the cell replicates all chromosomes once and then divides them
produces two new daughter cells each with 46 chromosomes
What happens when mitosis goes wrong?
Cells begin to divide uncontrollably
Becomes cancer
What does homologous mean?
Chromosomes are the same and contain the same genes in the exact same location
Mitosis processes in order;
prophase, metaphase, anaphase, and telophase, then cytokinesis( overlaps ana and telophase)
What occurs during first stage interphase?
DNA molecules duplicate and the centrioles replicate
What occurs during first stage prophase?
Nucleolus disappears
-nuclear membrane breaks down
Chromosomes appear as pairs of chromatids
Homologous chromosomes migrate towards cell equator then condense
Centrioles migrate to opposing poles of molecule
Spindle forms between these poles
What occurs during first stage metaphase?
Chromosomes line up on the cell equator
Each has a spindle fibre attached to it’s centromere
What occurs during first stage anaphase?
Pairs of chromatids separate to now be referred to as chromosomes (double chromatids)
Chromosomes then pull apart at the centromeres towards opposite ends of the cell
What occurs during first stage telophase?
Spindle disappears
Two nuclei form
One nuclear membrane
New nucleolus form in each new nucleus and each have diploid number (46 chromosomes)
What occurs during cytokinesis?
Division of cytoplasm
Separating cell into daughter cells
What is meiosis?
Cell division producing gametes with half the number of chromosomes of the parent cells (4 daughter cells)
What is the purpose of meiosis?
To produce gametes for fertilisation
Where does meiosis occur?
In sex organs i.e. testes and ovaries
What occurs during second stage prophase?
Chromosomes migrate-move toward the equator of cell
New spindle forms between the poles
What occurs during second stage metaphase
Chromosomes line up along the cell equator
What occurs during second stage anaphase
Chromosome split apart at the centromere
Two chromatid moves to opposite poles of cell
Resulting in chromatids remaining intact
Chromatid from one chromosome being at each pole
What occurs during second stage telophase
Nuclear membranes begin to form
Cytoplasm starts to divide (cytokinesis)
Four new cells formed (each have half number of chromosomes of original cell)
What is meant by centromere?
The link between 2 chromatids
What is a chromatid?
One of the two identical halves of a chromosome that has been replicated in preparation for cell division
What is cancer?
Uncontrolled cell division
What is a tumor?
Mass created by uncontrolled growth of abnormal cells
Difference between malignant and benign tumours
Malignant- may spread through body through metastasis
Benign- cannot invade normal tissues, blood, or lymph vessels/other body parts
Can be removed due to the tumour being surrounded by a capsule
Causes of cancer:
-carcinogens
-genetics
Types of carcinogens
-UV radiation
-X-rays
-Ionising radiation
-Viruses
-Chemical carcinogens
Cancer prevention:
-Education
-Legislation
What is spermatogenesis
The formation of spermatozoa in the testis
What is oogenesis
The formation of ova in ovary
Where does spermatogenesis occur?
Occurs within the seminiferous tubules in each testis
-seminiferous tubules are lined with immature cells called spermatogonia
Draw out process of spermatogenisis
- 2n Spermatogonium
- 2n spermatogonium (process mitosis) and 2N Spermatogonium
- 2n primary spermatocyte
- n x2 secondary spermatocytes (first meiotic division)
- x4 n spermatids (secondary meiotic division)
- x4 spermatozoa (maturation)
Draw out process of oogonium
- 2n oogonium
- 2X 2n oogonium
- 2n primary oocyte
- x2 n secondary oocyte and first polar body (first meiotic division)
- x2 n ootid and second polar body (second meiotic division
- Mature ovum n
