mitosis and meiosis Flashcards
what is the cell cycle
cell divides into 2 genetically identical daughter cells for growth, repair and asexual reproduction.
what are the 3 main stages of the cell cycle
-interphase
-mitosis
-cytokinesis
what are the 3 stages in interphase
G1, S phase , G2
what happens during G1?
the cell grows and new organelles and proteins(such as helicase DNA ,primase, DNA polymerase) are made
what happens during S-phase?
the cell continues to grow and proteins needed for cell division are made. the cell replicates its DNA ready to divide by mitosis and the ATP content is increased(DNA replication)
what happens during G2 phase?
the cell prepares to divide and some organelles increase in number
what is the role of meiosis?
-gives rise to genetic variation
-main role is the production of haploid gametes as cells have half the number of chromosomes
-produces genetically different cells
How does meiosis lead to genetic variation tho
By crossing over and independent assortment
what is independent assortment
the random arrangement/alignment of maternal and paternal chromosomes that can be distributed between the 2 daughter cells
what is crossing over
the exchange of alleles between non-sister chromatids or (between homologous chromosomes)
what is autosomal linkage
-when genes are located on the same chromosome
-the closer the loci of the genes on the chromosome, the more closely linked they are
-this is because they are less likely to be separated during crossing over/recombination in meiosis
what is sex linkage
-occurs on the 23rd chromosome
what happens during prophase
chromosomes condense and shorten
nuclear envelope dissintegrates
spindle fibres are formed
what happens during metaphase
chromosomes move to equator of cell
centromeres attach to spindle fibres at the equator
what happens during anaphase
the centromeres split
chromatids are pulled to poles of cell by spindle fibres
spindle fibres break down
what happens during telophase
the chromosomes unravel
2 nuclear envelope reforms
(last stage of mitotic division)
what happens during cytokinesis
2 genetically identical
constriction of the cytoplasm between the 2 nuclei
how do you calculate the mitotic index
number of cells with visible chromosomes divided by total number of cells
Mitosis practical method
