Mitosis and Meiosis Flashcards
What stage the of the cell cycle does cell division occur
M
What is G0
So not dividing. With signal can re-enter cell cycle e.g. liver cells neuron introduce era and never re-enter cell cycle
What are Telomeres
Repeated sequence TTA GGG non-coding DNA protects the chromsomes
Chromosome structure
Metacentric
sub metacentric
acrocentric
telocentric
Mitosis
Subdivision of somatic cells
production of two identical daughter cells
50 mitotic rounds during development
mitotic growth necessary for some tissues such as spermatogonia
Pro phase
Nuclear membrane begins to break away
chromosome condense
Centrioles migrate to different poles
nucleus disappears
Pro metaphase
Nucleus membrane disappears
kinetochore attached to the centromere
spindle fibres from centrioles attached to kinetochore’s
Anaphase
Spindle fibres pull on sister chromatides
centromere divides
sister chromatid migrate to opposite poles
telophase
Nuclear membrane reforms
Cchromosomes de condense
spindle fibres disappear
nucleolus reappears
cyto kinesis
Cytoplasm divides
Meiosis
Special subdivision for germline cells production of four nonidentical cells one round of replication followed by two rounds of division meiosisi 1 and 2 diploid reduced haploid production of egg and sperm
Pro phase 1
Nuclear membrane begins breakaway
chromosomes condense
centrioles migrate to different poles of cell
homologous pairs of chromoomes begin to find each other
homologous pairs lineup in twos
crossing over occurs between alleles of parental and maternal
Meta phase 1
Pairs of homologous chromosomes line up randomly
spindle fibres attached to kinetochore is attached to centromere
as variation as paternal and maternal Crimson’s line up randomly in twos
anaphase 1
Pair of cchromosomes separate
microtubules pull on homologous chromosomes
centromere and not divided
telophase 1
Nuclear membrane formed is
chromosome D condenses
spindle fibres disappear
meiosis II
Similar to mitosis
meiosis I vs meiosis II
Homologous pairs of chromosomes lineup separatel
Chromosomes lineup and chromatides separate
Consequences of meiosis
Maintaining constant chromosome number from generation to generation
Generation of genetic diversity
one- random assortment of chromosomes line up on metaphase plate randomly Metaphase I
two- crossing over of genetic material prophase I
Length of OOGenesis
12 to 15 years
Meiosis in making egg
Make three polar bodies, one big egg
What happens when meiosis goes wrong
. Third of all identified miscarriages
. Infertility
. The leading cause of mental retardation
Non-disjunction
Leads to aneuploidy, leads to mosaicism presence of two more signs in individual
Non-dysjuntion first pre-zygotic division
Non-mosaic karyotype
Non-disjunction later mitotic divisions
Mosaic karyotype
