2.3 Eukaryotic Cell Cycle + Division Flashcards
describe the difference between DNA normally and DNA during cell division
normally, DNA is all tangled
during cell divison, DNA condenses and appears as visible chromosomes
describe the process of DNA forming a visible chromosome
- DNA is a double helix
- DNA wraps around histone proteins to form a nucleosome
- nucleosome attaches into chromatin
- chromatin coils and supercoils and condenses into a visible chromosome
describe, in order, the events of the cell cycle
during interphase:
G1- cell assimilates molcules
- cell grows
S-phase- semi-conservative DNA replication
-replication of DNA
G2- cell synthesis of more organelles
during mitosis:
prophase
metaphase
anaphase
telophase
cytokinesisgive 4 key points of mitosis
- 2 new daughter cells made
- genetically identical to parent cells
- used for growth + replacement
- asexual reproduction
what happens during interphase in mitosis
cellular organelles double in number, the DNA replicates, and protein synthesis occurs. the chromosomes are not visible and the DNA appears as uncoiled chromatin
what happens during prophase in mitosis
- nuclear membrane and nucleolus break down
- centrioles migrate to opposite poles
- chromatin condenses to form visible chromosomes
- spindle fibres start to form
what happens during metaphase in mitosis
- chromosomes attach singly to the equator by centromere
- centromere attaches them on to the spindle fibres
what happens during anaphase in mitosis
- centromeres replicate
- sister chromatids split and move to opposite poles
what happens during telophase in mitosis
- nuclear membrane and nucleolus reform
- centrioles move away from poles
- chromatins reform (chromosomes decondense)
- spindle fibres break down
give 3 ways that growth can be defined as
a permanent increase in number of cells
a permanent increase in the mass of an organism
a permanent increase in the size of an organism
what are the three aspects of growth
cell division
assimilation
cell expansion
how are worn out or damaged cells replaced
by mitosis
describe asexual reproduction
involves one parent
no gametes involved
quicker than sexual reproduction
clones are genetically identical to parent
useful for extreme environments or solitary organisms
lots of different methods
describe sexual reproduction
requires two parents fusion of gametes occurs gametes are produced by meiosis more complex organisms offspring show genetic variation
describe binary fission as a process of asexual reproduction
involves mitosis and cytokinesis to make 2 offspring
describe spores as a process of asexual reproduction
involves mitosis and production of asexual spores- each spore grows into a new individual
describe regeneration as a process of asexual reproduction
some organisms can replace body parts when lost
describe bud production as a process of asexual reproduction
outgrowth from parent organism- a smaller, genetically identical organism is produced that then detaches and becomes independent
describe new plant structures as a process of asexual reproduction
vegetative propagation occurs in flowering plants. a new plant is propagated from the parent
is a gamete haploid or diploid
haploid
define homologous
same genes in the same places
what are the male gamete and site of production in animals
sperm cells in testes
what are the male gamete and site of production in plants
pollen in anther
what are the female gamete and site of production in animals
ovum in ovaries
what are the female gamete and site of production in plants
ovum in ovaries
give a summary of the two stages of meiosis
MEIOSIS I
normal interphase
different PMAT to mitosis
MEIOSIS II
no S-phase in interphase
no semi-conservative DNA replication
PMAT is the same as mitosis
what are the end products of meiosis
four genetically identical haploid gametes
describe interphase of meiosis I
same as mitosis
G1 , s-phase and G2 occur
describe prophase of meiosis I
nuclear membrane and nucleolus break down
centrioles migrate to opposite poles
chromatin condenses to form visible chromosomes
homologous chromosomes form bivalents
crossing over occurs; where nits of maternal and paternal chromosomes are cut and joined at random points called chiasma
describe metaphase of meiosis I
independent assortment occurs; either of a pair of homologous chromosomes, maternal or paternal, can move to either pole
describe anaphase of meiosis I
whole chromosomes move to opposite poles
describe telophase of meiosis I
centrioles move away from poles
nuclear membrane and nucleolus reform
chromatin reforms
spindle fibres break down
describe interphase of meiosis II
there is G1 and G2 but no s-phase so no semi-conservative DNA replication occurs
describe prophase of meiosis II
nuclear membrane and nucleolus break down
centrioles migrate to opposite poles
chromatin condenses to form chromosomes
spindle fibres start to form
describe metaphase of meiosis II
chromosomes attach singly to the equator by centromere
centromere attaches them on to the spindle fibres
describe anaphase of meiosis II
centromeres replicate
sister chromatids split and move to opposite poles
describe telophase of meiosis II
centrioles move away from poles
nuclear membrane and nucleolus reform
chromatin reforms
spindle fibres break down
what is a chromosomal mutation
a change in the large scale structure of a chromosome
describe the effect of a non-disjunction mutation on meiosis
during anaphase of meiosis II, the sister chromatids should split and move to opposite poles
in non-disjunction mutations, there is a failure of chromosomes splitting so both chromatids go to one poke
what effect does a non-disjunction mutation have on the gametes
one gamete will have two copies of a chromosome whereas another gamete will have none.
define aneuploidy
too little or too many chromosomes
give two examples of aneuploidy
trisomy
monosomy
what are the consequences of a non-disjunction mutation
it can be fatal
can cause Down’s syndrome, which is trisomy @ 21st chromosome pair
