cell reproduction Flashcards
mitosis
-cellular reproduction of 2 identical diploid daughter cells
-mitosis creates the 2 nuclei and cytokinesis splits the cell in two
-function = growth and repair in the body
meiosis
-production of gametes aka sex cells
-creates 4 unique haploid daughter cells through cellular divison
-function = to create cells for reproduction
why is cellular reproduction necessary for life?
-all cells come from other cells
-more cells need to be created or else organisms would stay exactly the same size and not be able to heal themselves
-also needed for reproduction to carry on the species
what is the difference between sister chromatids, chromosomes, and chromatin?
-sister chromatids make up chromosomes ( I )
-chormosomes are made up of 2 identical sister chromatids (X)
-chromatin is DNA appearing as thin strands/threads
-it is in this form during normal cellular processes (not mitosis) (~~~)
what happens during prophase (mitosis)?
-nucleolus dissapears
-nuclear envelope breaks down
-chromosomes are visible
-spindle fibers present
what happens during metaphase (mitosis)?
-chromosomes aligned at spindle equator (midway between spindle poles)
what happens during anaphase (mitosis)?
-sister chromatids separate and become daughter chormosomes
-puled ot opposite poles of the cell
what happens telophase (mitosis)?
-spindle fibers dissapear
-new nuclear envelopes formed around daughter chromosmes
when is DNA replicated?
-during S-phase of interphase
describe interphase
-majority of cell cycle
-made up of G1, S, and G2 phases
-if cell reaches G1 checkpoint and decides not to divide it goes into G0 (another part of interphase)
G1 interphase
-organelles double
-gathers materials for DNA snythesis
-makes final decision whether or not to divide
S phase of interphase
-DNA synthesis occurs
-each chromsome made of 2 sister chromatids
G2 interphase
-extends to onset of mitosis
-syntehiszes proteins for cell divison
why is cytokinesis different in plant and animals cells?
-plants have a cell wall around their membrane/cytoplasm so wall has to build itself between cells to divide them
-normally would not allow for cytokinesis
-animal cells do not have this wall so they can divide freely
what is the significance of chekpoints in the cell cycle?
-prevents cells from moving forward with mitosis if they are damaged
-check for growth signals and DNA correctness
-prevents them from passing on deformities to other cells (would lead to cancer)
-go through apoptosis if they are messed up
checkpoints in the cell (list and describe)
-G1: permits cell to divide (final decision to go through with mitosis)
-if not goes through G0 and does normal functions without dividing
-G2: verifying DNA is replicated
-if not it doesnt not go to M phase
-M: between anaphase and telophase of mitosis, makes sure chromosomes are properly attached to spindle fibers before pulling them to opposite ends
how are signals used for cell cycle control?
-signals control checkpoints which control if the cell halts the part of the cycle it is going through or keeps going
-if signals (like cyclins) are not present a cell will not continue on at the checkpoint
describe the two types of signals in cells
-internal: ex. cyclins
-come from inside the cell
-cyclins = present during certain stages of cell cycle (act as cellular timekeepers)
-if the appropriate cyclin in the correct level is not present the cell will not continue past checkpoints
-external: ex. kinases
-come from outside the cell
-kinases = remove phosphate from ATP and add it to other molecules
apoptosis vs. necrosis
-apoptosis is programmed cell death
-it is used to control the cell cycle and prevent deformities from spreading
-necrosis is unprogrammed cell death
-happens if something unexpected/bad happens and the cells die (like heart attack)
-causes inflammation and damage
apoptosis
-cell condenses on itself
-loses contact with neiighbots
-nuceus fragments
-plasma membrane blisters
-cell fragments
-engulfed by white blood/neighboring cells
how are chromosomes formed?
-chromatin is wound tighter and tighter around histones and nucleosomes so it can condense
what happens during prophase I?
-nuclear envelop fragments
-crossing over occurs
-spindle fibers form
-sister chromatids make up chromosmes that line up with homologus pairs
what happends during metaphase I?
-paired homologus chromosmes align at the spindle equator
-spindle fibers attack to chromosomes
what happends during anaphase I?
-homologues spearate adn moe to poles
-chromosomes still duplicated-
