Chapter 5: the mitotic cell cycle Flashcards
what is the centromere?
the section of the chromosome that holds the two chromatids together
why is mitosis important for growth?
- the two daughter cells are CLONES of the parent cells
- this allows the growth of multicellular organisms from unicellular zygotes
why is mitosis important for cell replacement?
cells that die are able to be replaced by identical cells
why is mitosis important for asexual reproduction?
- genetically identical offspring
- budding can occur
what does interphase consist of?
G1, S and G2 phases
what happens during the S stage?
DNA replication
what happens during the G1 stage?
growth and normal metabolic roles
-RNA, enzymes and other proteins needed for growth are made
what happens during the M stage?
mitosis
what happens during the G2 stage
growth and preparation for mitosis
- new DNA is checked and any errors usually repaired
- increase in the protein tubulin which is needed to make microtubules for the mitotic spindle
what happens during prophase?
- chromosomes appear
- chromatin coils up
- centrosomes replicate before prophase
what happens during the second stage of prophase?
- nuclear envelope breaks up
- nucleolus disappears
- chromosomes seen to contain two identical chromatids
what happens during metaphase?
- each centrosome reaches a pole
- chromosomes line up along equator of spindle
- they are attached to the spindle by their centromeres
what happens during anaphase?
- chromatids move to opposite poles
- they are pulled by microtubules
what happens during telophase/ cytokinesis?
- chromatids uncoil
- cytoplasm and cell divide into two by constriction from the edges of the cell
- nucleolus reforms
- nuclear envelope reforms
- centrosome will replicate again during interphase
what are telomeres?
- short DNA base sequences that are repeated
- lots of G and C
what is the function of telomeres?
- they ‘seal’ the DNA
- they make sure that the ends of the molecule are included when DNA replicates
how do telomeres work?
- they add more bases using a copying enzyme called telomerase
- the extra DNA that the telomerase adds are the telomeres
what is the potency of a cell?
the extent of the power of a stem cell to produce different cell types
what is the definition of multipotent?
can only produce a few types of cell
what is a mutation?
a change in any gene
what is an oncogene?
a mutated gene that causes cancer
what is the definition of a malignant tumour?
a tumour that interferes with the normal functioning of the area where it has started to grow
what are secondary growths?
cells that break off and spread to other parts of the body
what is metastasis?
the spread of cancers
how is mitosis different in plant cells?
- do not contain centrosomes
- after nuclear division, a new cell wall must form between the daughter nuclei
