D2.1 Cell and Nuclear Division Flashcards
Define cytokinesis (2)
physical process of cell division
divides cytoplasm of parental cell into 2 daughter cells
Define the mother cell
parent cell/original cell
Define the daughter cell
mother cell divides into 2 daughter cells
Prokaryotic division
divide by binary fission
Eukaryotic division
divide by mitosis or meiosis
How cytokinesis works for animal cells (2)
network of actin + myosin proteins form a contractile ring that pinches cell membrane together
forms a cleavage furrow - deepens and forms 2 separate daughter cells
How cytokinesis works in plant cells (2)
formation of cell plate - created by fusion of vesicles containing cell wall material (cellulose)
cell plat grows outward until it reaches the existing cell wall that it fuses with
Describe equal cell division (2)
daughter cells receive at least 1 mitochondria + other organelles come from existing parent cells
produces 2 cells of the same size
2 examples of unequal cell division
Oogenesis
Budding in yeast
Describe oogenesis (3)
primary oocyte (2n) performs cell division + releases first polar body (n)
Secondary oocyte loses a second polar body and become ovum
ovum fertilised by sperm cell to form zygote
Describe Budding in yeast (3)
type of asexual reproduction
bud starts small then grows until it becomes a fully developed cell
daughter cell is is typically smaller than parent cell and receive less than half of cytoplasm + organelles
Define mitosis (2)
process of nuclear division before a cell physically divides into 2
cell’s DNA is copied into 2 daughter cells before mitosis
Define interphase (2)
stage where DNA is replicated
occurs before mitosis
Stages of mitosis (4)
prophase
metaphase
anaphase
telophase
Importance of mitosis (2)
how organisms grow
important for asexual reproduction
Structure of chromosomes (2)
chromosomes are only visible during cell division
2 chromatids joined at centromere to form x-shape
Describe early prophase (4)
chromosomes become more distinct
coil up
shorten
thincken
Describe late prophase (3)
centrioles move towards opposite poles of the cell
nucleolus shrinks + disappears
nuclear envelop disintegrates
Describe metaphase (2)
centrioles at poles grow/produce spindle fibers
spindle fibres attach to centrometre of chromosomes
Describe anaphase (3)
spindle fibres contract
chromatids are pulled to opposite poles of cells by their centromere
each pole receives one chromatid from each chromosome
Describe telophase
Define cell proliferation (2)
process of cellular division/replication
increases cell number and/or organism size + complexity
Stages of interphase (4)
first growth phase
G0 phase
synthesis phase
second growth phase
Functions at site of interphase (4)
DNA replication + checked for errors
protein synthesis
mitochondria + chloroplasts grow and divide
metabolic functions
First growth phase of interphase (3)
proteins are synthesized
organelles replicate
cell increases in size
Synthesis phase of interphase
DNA is replicated in the nucleus
Second growth phase of interphase (3)
cell continues to increase in size
energy stores increase
duplicated DNA checked for errors
G0 phase of interphase
cell moves out of the cell cycle
can be permanent or temporary
Reasons for G0 phase of interphase (2)
cell becomes specialised to carry out particular function
DNA is damaged - cell division may no longer be viable
cyclin D level of G1 phase
cyclin D levels gradually increase
cyclin E level of S phase
cyclin E is used for DNA replication + promotes centromere duplication
cyclin A level of G2 phase
helps induce DNA replication
cyclin B level of mitosis
essential for formation of mitotic spindles + alignment of chromatids
Define malignant tumour (2)
cancer cells in tumour spread to other parts of body
sometimes recur after it is removed
Define benign tumour (2)
localised and does not spread to other parts of body
most respond well to treatment
Stages of meiosis (2)
Meiosis 1
Meiosis 2
Meiosis 1 Prohpase 1
chromosomes condense
nuclear envelope disintegrates
spindle fibres form on poles
crossing over - exchange of equivalent DNA between non-sister chromatids
DNA molecule of one chromatids is cut + second cut is made at same point of other chromatid from other parent (non-sister)
DNA sections are swapped between parent chromosomes
Meiosis II
