3.7 Mitosis Flashcards
Define mitosis.
cellular division which results in two identical daughter cells, each having the same number of chromosomes as the parent cell
What is the period preceding mitosis called, and what happens during it?
-interphase
-cell grows and doubles its DNA (copies remain attached at the centromere) in preparation for division
Describe the first stage of mitosis, prophase.
-chromosomes become visible, nucleolus disappears and nuclear envelope breaks down
-spindle apparatus forms
-(in animal cells) centrioles move to opposite poles of the cell
Describe the second stage of mitosis, metaphase.
-spindle fibres attach to the centromeres of the chromosomes, which arrange across the equator of the cell
Describe the third stage of mitosis, anaphase.
-centromeres divide into two and the spindle fibres pull the individual chromatids (which make up the chromosome) apart
-chromatids move to opposite poles and are now called chromosomes
Describe the fourth stage of mitosis, telophase.
-chromosomes decompress back into chromatin
-spindle apparatus disintegrates
-nuclear envelope and nucleolus forms
-cytoplasm divides
Define cytokinesis.
the division of cytoplasm after mitosis/meiosis, separating into its daughter cells
Describe binary fission in prokaryotic cells.
-circular DNA replicates and both copies attach to the cell membrane (plasmids also replicate)
-cell membrane grows and pinches inward between the two DNA molecules, dividing the cytoplasm in half
-a new cell wall forms between the two DNA molecules, resulting in two daughter cells with a copy of DNA each and varying numbers of the plasmids in the parent cell
Describe replication of viruses.
-virus attaches to host cell with its attachment proteins
-viral nucleic acid is injected into host cell, and the genetic information on it results in the host cell’s metabolic processes to produce the viral nucleic acids, proteins, and other components, which then assemble into new viruses
List three reasons for mitosis to occur.
-growth (e.g. of a new organism formed by two haploid cells fusing)
-repair (e.g. replacement of dead or damaged cells with those identical to those lost)
-reproduction (e.g. of monocellular organisms)
Suggest a disadvantage of genetically identical offspring.
none are more or less adapted to their environment; change is much more likely to wipe out an identical population than one with variation
Suggest an advantage of genetically identical offspring.
individuals will not have to expend time and energy on finding a partner to reproduce with
