Cell Division, Diversity And Differentiation Flashcards
In the cell cycle,
M is the ________
G, S are part of the ______
division phase (mitosis/meiosis) interphase
What are checkpoints in the cell cycle for?
prevent uncontrolled division (lead to tumors), repair damage to DNA
What happens in the M phase of the cell cycle?
chromatin condenses
the checkpoint ensures that the cell is ready for mitosis
cell growth stops and mitosis occurs
What happens in the G₀ (gap 0) phase of the cell cycle?
resting
apoptosis (programmed cell death)
differentiation
What happens in the G₁ phase of the cell cycle?
growth phase, cell grows
checkpoint ensures ready to enter S phase
transcription of genes to RNA
organelles duplicate
What happens in the S (synthesis) phase of the cell cycle?
rapid phase (reduces mutation)
chromosomes unwind
DNA replicates
genes that are active in all cells replicate first
What happens in the G₂ phase of the cell cycle?
chemicals ensure the cell is ready for mitosis
stimulate proteins which make chromosomes condense to spindle
cells grow
Mitosis prophase is when…
2 sister chromatids shorten, thicken as DNA coils, nuclear envelope breaks down,
centrioles move to poles,
cytoskeleton protein threads form spindle between centrioles
Mitosis metaphase is when..
pairs of chromatids attach to spindle threads in middle and are attached by their centromeres.
Mitosis anaphase is when…
pairs of chromatids are pulled apart, the centromere splits,
motor proteins pull chromatids in opposite directions to poles
they are now chromosomes
Mitosis telophase is when…
cytokinesis is when…
chromosomes reach the poles
nuclear envelope forms around the chromosomes
now there are 2 identical nuclei
the cytoplasm splits leading to 2 new daughter cells.
Meiosis is…
a type of nuclear division that results in the formation of gametes.
Haploid
one set of chromosomes (23)
2 gamete nuclei fuse = …
diploid zygote
Homologous chromosomes
matching
containing same genes, same place
same genes but different alleles (variants)
What happens in the S phase of interphase, in Meiosis?
chromosomes are duplicated as the DNA is replicated
now, each chromosome consists of 2 sister chromatids
in meiosis, chromosomes pair with homologous pair.
Meiosis prophase 1
chromatin condenses, supercoils
nuclear envelope breaks down
microtubules form from centrioles
chromosomes come together in homologous pairs, each member consists of 2 chromatids
crossing over occurs (non-sister chromatids wrap, swap sections, alleles shuffled)
Meiosis metaphase 1
line in middle, attach to spindle thread by centromere
independent assortment occurs (homologous pairs arranged randomly) = determines how pulled apart
Meiosis anaphase 1
pair of homologous chromosomes pulled apart by motor proteins
each chromosome has 2 chromatids
Meiosis telophase 1
and after?
nuclear envelope forms
cell divides by cytokinesis
then there’s a short interphase when chromosomes uncoil (each chromosomes = 2 chromatids)
Meiosis prophase 2
nuclear envelope breaks down
chromosomes coil and condense
chromatids of each chromosomes are no longer identical
spindles form
Meiosis metaphase 2
chromosomes attach by centromere to middle of the spindle
chromatids randomly arrange
Meiosis anaphase 2
centromeres divide
chromatids pulled apart by motor proteins towards poles
chromatids randomly segregated