Cell Cycles Flashcards
Features of prophase…
-nuclear membrane begins to breakdown
- centrioles move to poles
- chromatin supercools and condense in chromosomes
Features of metaphase…
- spindle fibres form
- spindle fibres attach
- to centromere of chromosomes
- chromosomes align at equator
Features of anaphase…
- spindle fibres shorten
- centromere splits
- sister chromatids separated
- chromatids pulled to opposite poles of cell
Features of telophase…
- nuclear membrane begins to reform
- chromosomes unwind
What are homologous pairs of chromosomes?
- two chromosomes that carry the same genes in the same loci
What should be done when counting cells to make sure mitotic index obtained is accurate?
- examine large number of cells
- for representative sample
- repeat count
- ensure figures are correct
- method to deal with parts shown at edge
- standardise counting
Differences between mitosis and meiosis.
Mitosis
- one division
- daughter cells genetically identical
- 2 daughter cells
- diploid
- no crossing over
- no independent segregation
Meiosis
- two divisions
- daughter cells genetically non-identical
- 4 daughter cells
- haploid
- crossing over
- independent segregation
How does meiosis result in haploid number of chromosomes and genetic variation?
- homologous chromosomes pair up
- maternal and paternal chromosomes arranged in ANY order
- independent segregation
- crossing over
- new combo of alleles
Process of crossing over…
- homologous pairs of chromosomes associate
- chiasmata form
- alleles exchanged
- new combo of alleles
Process of independent segregation…
- maternal and paternal chromosomes reshuffle in any combination
- new combo of alleles
Process of meiosis…
- DNA replication in late interphase
- two divisions
- separation of homologous chromosomes
- separation of sister chromatids
- produces 4 genetically non-identical haploid cells
Describe binary fission…
- replication of circular DNA
- replication of plasmids
- division of cytoplasm
What happens during interphase?
- G1 = increase in cell size
- S phase - Semi-conservative replication
- G2 = synthesis and stores of ATP, synthesis of organelles
What occurs at cytokinesis - mitosis?
- cytoplasm divides producing 2 genetically identical diploid cells
What is a tumour?
- mass of cells
- by uncontrolled cell division
