5. Mitotic Cell Cycle Flashcards
How many chromosomes in human cells?
46
2 identical chromatids of a chromosome?
sister chromatid
Centre of a chromosome?
centromere
What is mitosis?
the division of a nucleus into 2 identical daughter cells
Describe the mitotic cell cycle
interphase: G1, S, G2
mitosis/nuclear division
cytokinesis
What is G1?
gap 1, where the cell grows
What is S?
DNA synthesis, centrosome replicates
What is G2?
gap 2, the cell continues to grow and new DNA made during S phase is checked
What are the stages of mitosis?
prophase
metaphase
anaphase
telophase
Describe prophase
1) nucleolus disappears, nuclear envelope breaks down
2) centrosomes move to opposite poles
3) visible chromosomes as the chromatin coils up, chromosomes seen to have 2 identical chromatids
Describe metaphase
metaphase: middle
1) chromosomes line up in the middle
2) spindle fibres start to form from the centrosomes at opposite poles
Describe anaphase
anaphase: apart
1) spindle fibres attach to the centromeres
2) sister chromatids are pulled apart, forming V shapes
3) centromere split in half
Describe telophase
1) nuclear envelope reforms, nucleolus reappears
2) chromatin uncoils
What is cytokinesis?
the division of the cytoplasm and cell into 2 when the cell membrane constricts
Where in the centromere do spindle fibres attach?
kinetochore
What do microtubules do to pull the sister chromatids apart?
shorten
What is mitosis for? (3)
1) growth of multicellular organisms from unicellular zygote (gamete + gamete)
2) repair of tissues by replacement of dead/damaged cells
3) asexual reproduction
What are telomeres?
repetitive sequence of DNA found at the ends of chromosomes, protects genes from chromosome shortening that results from each cell division
What enzyme adds bases to the telomeres?
telomerase
What happens when telomeres run out?
When the vital DNA is no longer protected, the cell dies.
What is a stem cell?
a cell that can divide an unlimited number of times by mitosis.
each new cell it produces can either remain a stem cell or differentiate into a specialised cell
What is potency?
the power of a stem cell to produce different types of cell
What are totipotent cells?
cells that can produce any type of cell
The more specialised a cell is…
…the more they lose their ability to divide by mitosis
Define mutation
a change in any gene
What is a mutated gene that causes cancer called?
oncogene
What are the 2 types of tumours?
benign and malignant
What is it called when secondary tumours form by spreading through the blood and lymphatic system?
metastasis
