diploid
two copies of every chromosome (2n), one from each parent
rapid and effective reproduction that makes clones of the parent. any genetic variations are due to mutations or errors. prokaryotes do this (binary fission) and eukaryotes can do this too
asexual reproduction
one copy of every chromosome (n=23 in people), one homolog from each pair. gametes.
haploid
ori (origin)
region of chromosome. where replication starts
diplontic life cycle
animals and plants life cycle, gametes are only haploid stage. then it fuses to form diploid in fertilization. all other stages and all cells are diploid.
cell cycle
the time from one cell division to the next cell division. 2 phases in eukaryotes: interphase (long G1, S, G2) and M phase (mitosis and cytokinesis)
metaphase
3rd phase of mitosis. chromosomes line up at midline (metaphase plate) of the cell
point where genetic material is echanged between homologous chromosomes
chiasmata
occurs during anaphase 1, it is a matter of chance as to which chromosomes (maternal or paternal) go to which daughter cell / gamete.
independent assortment
fertilization
process where two haploid gamtes fuse to form a zygote during sexual reproduction
replicates DNA. part of cell division. only occurs in S phase (synthesis)
replication
interphase
part of cell cycle. in between rounds of mitosis. longest part. chromatin is not condensed (DNA loosely wrapped around protein histones). includes G1 (normal cell job), S (DNA replication), G2 (preparing for mitosis)
astral microtubules
type of microtubules in spindle. interact with cell membrane and help keep poles apart
4th phase of meiosis. separating homologous pairs into chromosomes that to opposite poles
anaphase I
a meiosis error. if a homologous pair or chromatids do not separate at anaphase I or II. this causes aneuploidy
nondisjunction
important for reproduction, growth and repair of tissues. 4 events: reproductive signal, replication, segregation and cytokinesis
cell division
chromatid, sister chromatids
half of a chromosome. every chromosome has 2. this is a molecule of DNA. connected by centromere at center. made when chromosome is replicated in S phase
centrioles
2 of these make up centrosomes. these are hollow tubes formed by microtubules
1st phase of meiosis. can last a long time (decades in females, month in males). chromatin condenses. difference - homologous chromosomes pair up (synapsis). this forms a tetrad (4 chromatids). these homologs cross over at chiasmata
prophase I
centrosome
in prophase, poles where chromosomes are moved to. one at each end of the cell
chromosomes
condensed and compact chromatin that appear during prophase. they get wrapped tightly! composed of two chromatid
region where chromatids are joined together
centromere
cytokinesis
division of cytoplasm and separation of the two new cells. with a contractile ring. part of cell division. happens after mitosis in M phase
interphase
long part of cell cycle. G1 (gap 1), S (DNA synthesis / DNA replicates) and G2 (gap 2)
minus end-drected motor protein at kinetochores. move chromosomes along microtubules towards poles by hydrolyzing ATP for energy or microtubules shortening
cytoplasmic dynein
centromere
region where chromatids are joined together
in prophase, poles where chromosomes are moved to. one at each end of the cell
centrosome
protein structures on centromere. microtubules attach here. important for moving chromosomes
kinetocore
type of microtubules in spindle. attach to kinetochore on chromatids to pull chromatids apart
kinetochore microtubules
anaphase I
4th phase of meiosis. separating homologous pairs into chromosomes that to opposite poles
