chapter twelve Flashcards
what does cell division result in?
2 daughter cells
what is the purpose of cellular division?
reproduction, growth, repair
unicellular cell division
clones
- ex. amoeba
multicellular cell division
- reproduction (some organisms that don’t form gametes - asexual/sexual)
- growing (embryo, new blood cells)
- differentiating (which genes where expressed when)
- repair
genome
a cell’s DNA/genetic information
chromatin
entire complex of DNA and proteins that make up chromosomes
what is the purpose of protein in DNA?
combats negative charge of nucleotides
chromosomes
structures composed of chromatin
- eukaryotic (long DNA molecule w/ many proteins)
- after S phase, they have sister chromatids
sister chromatids
joined copies of the original chromosome
- attached by cohesions
centromere
region made up of repetitive sequences in the chromosomal dNA where the chromatid is attached most closely to a sister chromatid
- where kinetochores bind
homologous chromosomes
pair of chromosomes that have same order of genes but with some variation
somatic cells
diploid
- 2n number of chromosomes
gametes
haploid
- n number of chromosomes
mitosis
division of genetic material in the nucleus
cytokinesis
division of the cytoplasm
- follows mitosis
what do the cell division cycles consist of?
alternating M ( mitotic - mitosis/cytokinesis) phase with interphase (90% of cycle)
3 phases of interphase
- G1 phase
- S phase
- G2 phase
G1 phase
first gap, metabolic activity/growth
S phase
“replication”, synthesis/duplication of chromosomes, metabolic activity
G2 phase
second gap, metabolic activity/growth, preparation for division
stages of mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
spindle
fibers made of microtubules and proteins
- elongate by polymerizing and incorporating more tubulin
kinetochore
structure made up of proteins that have assembled on specific sections of DNA at each centromere
- where spindle attaches during prometaphase
centrosomes
the of microtubule-organizing center
- aster
aster
radial array of short microtubules that extend from each centrosomes during division
how many centrioles are in centrosomes in animal cells?
2
prophase
- chromosomes (as chromatin) become condensed
- spindle appears between centrosomes
- nucleolus disappears
- centrosomes pushed away from each other
prometaphase
- nuclear envelope fragments
- microtubules attach to kinetochores
metaphase
- chromosomes arrive at metaphase plate (equidistant between spindle’s poles)
- kinetochore microtubules and nonkinetochore microtubules
kinetochore microtubules
jerk chromosomes back and forth, attached to kinetochores
nonkinetochore microtubules
interact w/ those from opposite poles of spindle to lengthen cell
anaphase
- sister chromatids separate
- chromosomes move to opposite ends of cell
telophase
- reversal of prophase
- each cell gets new nuclear envelope
cytokinesis
- splitting of cytoplasm through cell plate or cleavage furrow
cleavage furrow
- animal cells
- pinches cell in 2
- shallow groove near old metaphase plate
- actin filaments - ring of actin filaments (contractile) on cytoplasmic side, interacts w/ myosin to contract
cell plate
- plant cells
- vesicles move along microtubules to middl elf cell and coalesce
binary fission
cell grows to double its size then divides
- duplicates of DNA attached to plasma membrane
- used by prokaryotes/bacteria
what is another name for mitosis
karyokinesis
how many chromosomes present in interphase
46
number of chromosomes in each mitotic phase
prophase, prometaphase, metaphase - 46
anaphase - 92
cytokinesis - 46 in each of 2 cells
