week 7 Flashcards
zygote
2 parent gametes that fertilize to form diploid cells or zygotes
cell cycle
a highly regulated series of events that lead to cell division (when cells are ready to divide they become compact)
cytogenetics
field of genetics involving microscopic examination of chromsomes
karyotype
a photographic representation of chromosomes
homologous chromosomes
in diploid species, members of a pair of chromosomes
eukaryotic chromosomes
occur in sets
on set has 23 chromosomes
22 autosomes
humans have 2 sets 46 total
two chromosome sets
diploid or 2n
gamete
sperm and eggs have only 1 set of chromosomes = haploid or n
interphase
g1
s phase
g2
m
G1
(11 hours)
first gap
accumulates molecular changes that promote progression through cell cycle
s phase
(8 hours)
chromosome replication produces 6 pairs of sister chromatids
G2
(4 hours)
nucleus breaks apart, and replicated chromosomes condense in preparation for mitosis
some growth may occur
M phase
(1hour)
sister chromatids separate during mitosis, and 2 cells are formed during cytokinesis (2 daughter cells containing 6 chromosomes each)
3 critical checkpoints
g1, g2, metaphase
mitotic cell division
cells divide to produce two new cells (daughter cells) genetically identical to the original (mother cell)
the spindle apparatus
a structure composed of microtubules, responsible for organizing and sorting the chromosomes
mitosis
making 2 daughter cells from 1 original cell
Mitosis pneumonic (stages in order)
PPMAT
prophase
prometaphase
metaphase
anaphase
telophase
cytokinesis
prophase
chromatids condense into highly compacted structures that are readily visible by microscope
- nuclear membrane begins to dissolve into small vesicles, nucleolus no longer visible
prometaphase
nuclear envelop completely fragments and spindle apparatus is fully formed
sister chromatids become attached to kinetochore microtubules from opposite poles
metaphase
Characterised by pairs of sister chromatids aligned in a single row along a plane halfway between the poles called the metaphase plate
anaphase
connections between sister chromatids are broken & kinetochore microtubules shorten, pulling chromosomes toward the pole to which
telophase
chromosomes reach their respective poles and decondense
nuclear membranes re-form to produce two separate nuclei
cytokinesis
happens quickly after mitosis
animals- cleavage furrow constricts like a drawstring to separate the cells
plants - vesicle from the Golgi apparatus from a cell plate, which forms a cell wall between the two daughter cells
end result of mitosis
two daughter cells with the same number of chromosomes as the mother cell
barring mutations, two daughter cells are identical
meiosis
takes cell chromosome number and reduces it to half (diploid->haploid)
meiosis 1 key events
- homologous pairs of chromosome segments form bivalent in the process of synapsis
- crossing over results in physical exchange between chromosome segments from the bivalent
steps of meiosis I
prophase I
pro metaphase I
metaphase I
anaphase I
telophase I
cytokinesis
meiosis I results in…
2 haploid cells with no pairs of homologous chromosomes
prophase I
replicated chromosomes condense, bivalents form, and the nuclear membrane starts to fragment
pro metaphase I
spindle apparatus is formed, and kinetechore microtubules attached to sister chromatids
metaphase I
bivalents are organized along metaphase plate as a double row
anaphase I
segregation of homologs occur
connections between bivalents break, but sister chromatids stay connected together
each joined pair of chromatids migrates to one pole, while homologous pair moves to the opposite pole
Telophase I
sister chromatids have reached their respective poles and decondense; nuclear membranes reform producing two separate nuclei
meiosis II
separates sister chromatids
DNA is not replicated between meiosis I and II
sorting events of MII are similar to those of mitosis but starting point is different
mitosis - meiosis I - meiosis II
two diploid daughter cells - 2 haploid cells - 4. haploid daughter cells
