mitosis and meiosis Flashcards
meiosis
generates gametes
gametes
sex cells
zygote
fertilized egg
mitosis
chromosome duplication portion of cell division
binary fission
cell replication in prokaryotes
budding
cell replication in unicellular eukaryotes (division by mitosis)
nucleosome
a structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of histones
histones
proteins that act as spools around which DNA
winds to create structural units called nucleosomes
chromatin
a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms; provides organization to genetic material
chromatid
one half of a duplicated chromosome. Before replication, one chromosome is composed of one DNA molecule.
chromosome
a long DNA molecule with part or all of the genetic material of an organism
somatic cell
any cell not a sex cell
karyotype
an individual’s complete set of chromosomes
diploid
chromosomes are in pairs
haploid
one chromosome not paired, found in meiosis
diploid
pair chromosomes, found in humans and mitosis
polyloid
triple chromosome, found in other organisms
stages of cell cycle
- interphase
- mitosis
- cytokinesis
stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
stages of interphase
- G1
- S
- G2
G1 phase
cell grows
S phase
DNA is replicated
G2 phase
more cell division replication
when does mitosis occur
between G2 and G1
what happens during prophase
- chromosomes condense and become visible
- spindle fibers emerge from centrosomes
- nuclear envelope breaks down
- nucleolus disappears
what happens during prometaphase
- chromosomes continue to condense
- kinetochores appear at the centromeres
- spindles attach to the kinetochores
- centrosomes move towards opposite poles
kinetichore
proteins on the centrosome where the microtubules attach to
what happens during metaphase
- spindle is fully developed
- chromosomes lined up
- each sister chromatid is attached to a spindle
what happens during anaphase
- cohesion proteins break down
- sister chromatids are on opposite sides
- non kinetochore spindles lengthen to elongate the cell
what happens during telophase
- chromosomes decondense on opposite sides
- nuclear envelope surrounds each cluster of chromosomes
- spindle fibers break down
cytokinesis (animal)
cleavage furrow separates the cells
cytokinesis (plant)
a cell plate separates the daughter cells
cell cycle checkpoints
surveillance mechanisms that monitor the order,
integrity, and fidelity of the major events of the cell cycle
purpose of cell cycle checkpoints
Prevents proliferation of abnormal or defective cells
whats in the G1/S checkpoint
-cell size
-DNA damage
- growth factors
- nutrients
s phase checkpoint
- DNA damage
G2/M checkpoint
-cell size
-DNA replication
M checkpoint
check for chromosome attachment to spindle
autosome
any chromosome other than a sex chromosome
homologous chromosomes
chromosome that have the same genes in the same position and have the same size and shape; aka homologs
sister chromatids
two identical chromatid copies in a replicated chromosome
3 phases of meiosis
- interphase
-meiosis 1 - meiosis 2
meiosis interphase
chromosomes replicate
meiosis 1
- crossover occurs
- chromosomes are separated in 2 cells
meiosis 2
sister chromatids separate to make 4 daughter cells
cohesin
hold 2 sister chromatids together
what happens in meiosis G1 phase
cell growth
S phase of meiosis
DNA replication
synapsis
pairing of two homologous chromosomes
synaptonemal complex
lattice of proteins that connects paired homologous chromosomes
tetrad
Bivalent; a group of two homologous chromosomes
chiasma(ta)
point of contact between two non-sister chromatids belonging to homologous chromosomes; become visible after crossing over
what happens dearly early prophase 1 of meiosis
- homologous chromosomes condense
- synapsis begins
- tetrads form
- crossover
what happens during prometaphase 1 of meiosis
- homologous chromosomes are connected to the spindles at the fused kinetochore that is shared by the sister chromatids
- nuclear envelope disappears
what happens in metaphase 1 of meiosis
-random assortment in the middle
-crossovers with non-sister chromatids
anaphase 1 meiosis
chromosomes are pulled to the ends of the cell. sister chromatids are still attached at the centromere
Telophase 1 and cytokinesis of meiosis
sister chromatids arrive at the poles. nuclear envelope forms around each nucleus. cleavage furrow divides the cytoplasm
what do we have at the end of meiosis 1
two daughter cells genetically distinct from the parent cell
turner syndrome
45, XO; short stature, delayed puberty, infertility, heart defects, and certain learning
disabilities
klinefelter syndrome
47, XXY; low testosterone and reduced muscle mass, facial hair, and body hair,
infertility
trisomy 21
7,XY,+21 or 47,XY,+21; Down Syndrome