ch 4- the cell cycle Flashcards
what are the 3 purposes of cell replication
growth and development
maintenance and repair
reproduction
binary fission
the method of cell replication used by prokaryotes
allows a single bacterium to replicate exponentially in a short period of time
what is the process of binary fission (overview)
DNA replication
Elongation
Septum formation
Cell Division
what occurs in DNA replication
the circular chromosomes uncoil and the DNA is replicated. the plasmids also replicate
asexual reproduction
a method of reproduction that produces genetically identical cells without the fusion of gametes
plasmids
a small circular loop of DNA that is separate from a chromosome, typically found in bacteria
what occurs in elongation
the cell will elongate to prepare to separate into two new cells and the duplicated circular chromosomes migrate to opposite sides of the cell
what occurs in septum formation
as the cell undergoes cytokinesis by pinching inwards, thus creating a septum. as plasmids replicate independently of the circular chromosome, they won’t always be evenly distributed between the two cells
what occurs in cell division
as a new cell wall and membrane are formed down the centre of the cell, two new genetically identical cells are formed
cytokinesis
the division of the cytoplasm and formation of two daughter cells
septum
dividing wall formed during binary fission
what are the 3 stages of the eukaryotic cell cycle
interphase — cellular growth and duplication of chromosomes
mitosis — separation of sister chromatids and the formation of two new nuclei cytokinesis — division of the cytoplasm and formation of two daughter cells.
interphase
the first stage of the eukaryotic cell cycle which involves cellular growth and duplication of chromosomes. Composed of three phases: G1, S, and G2
chromosome
a structure composed of DNA tightly wrapped around histone proteins. Carries the genetic information (genes)
of a cell
mitosis
the second stage of the eukaryotic cell cycle, which involves the complete separation of sister chromatids and nuclei
sister chromatids
the two identical halves of a replicated chromosome
interphase- overview
first and longest stage
the cell synthesises the necessary DNA, proteins and organelles required for growth and replication.
DNA in the nucleus exists as long chromatin threads
there are 3 substages
chromatin
chromosomes (DNA and proteins) that have been unwound and loosely packed during interphase
Gap 1 (G1) phase- SIR
Synthesising proteins for DNA replication
Increasing the volume of its cytosol
Replicating its organelles
will either proceed to S or G0
Gap 0 (G0) phase
quiescent- dormant cells that can re-enter the cell cycle
terminally differentiated- cells that have fully specialised and no longer replicate
Synthesis (S) phase
chromosomes turn into 2 identical sister chromatids held together by a centromere
our non-reproductive/somatic cells are diploid, 2 sets of paired chromosomes (2n)
Gap 2 (G2) phase
volume of the cytosol increases
synthesises proteins in preparation for mitosis
mitosis
separation of sister chromatids through PMAT and separates te DNA so that a complete genome is present in each daughter cell
prophase
DNA is condensed and wrapped around histones, producing visible chromosomes
centrioles migrate to the poles of the cell, spindle fibres start to form
metaphase
chromosomes align in the equator of the cell, spindle fibres connect to chromosomes. M for middle
anaphase
spindles contract, pulling apart the chromatids and splitting the centromere. the sister chromatids pull away from each other, cleavage furrow starts to form
A for away
telophase
chromosomes decondensed at the opposite ends and new nuclei form around them. the spindle fibres break down
cytokinesis in animal cells
a cleavage furrow forms. a loop forms, pinching the two plasma membrane
cytokinesis in plants
a cell plate is produced between daughter cells to produce the cell wall
what are the 3 checkpoints
G1 checkpoint, G2 checkpoint, metaphase checkpoint
gap 1 checkpoint
cell size- is it large enough?
replication of proteins- are there enough?
dna- is it mutation free?
gap 2 checkpoint
check for replicated DNA and that theres enough resources for mitosis
metaphase checkpoint
checks the alignment of chromosomes and the spindle fibre formation
apoptosis
programmed and controlled cell death
what are the two methods that apoptosis can be triggeerd
the mitochondrial pathway- intrinsic or the death receptor pathway- extrinsic
what is the mitochondrial pathway in apoptosis
the mitochrondria detects damage or malfunction-> releases cytochrome c-> binds with cytosolic proteins forming apoptosomes-> activates caspase enzymes-> initaties apoptosis
what is the death receptor pathway in apoptsos
death signalling molecules are recognised by death receptor proteins on the surface -> released by immune cells -> bind to death receptor protein -> initiates caspase enzymes -> initiates apoptosis
what are the apoptosis stages
caspases activated by mitochondrial/external death receptor -> digest intracellular materials -> cell shrinks, nucleus condenses, blebs -> bulging of plasma membrane to form apoptotic bodies -> cytoskeleton breakdown also forms apoptotic bodies -> phagocytosis where the phagocytes eat the damaged cell
caspase enzymes
catalysts that cleave specific intracellular proteins during apoptosis
cytochrome c
a protein embedded in the inner mitochondrial membrane
blebbing
the bulging of the plasma membrane to form apoptotic bodies
apoptotic bodies
vesicles containing cell contents that are released from a dying cell during apoptosis and engulfed by phagocytes
phagocytes
a cell of the immune system responsible for engulfing and destroying harmful microorganisms and foreign material
phagocytosis
endocytosis of solid material or food particles
necrosis
the unregulated cell death initiated by damage. the cell will swell and burst, releasing its contents into the environment. inflammation and damage will occur to nearby cells and tissues
regulatory genes
found at each checkpoint and produce regulatory proteins which control the expression of other genes
regulatory proteins
regulate or determine whether errors at the checkpoints should undergo repair or apoptosis
what are 2 factors that mutations occur from
mutagens and carcinogens
mutagens
induce genetic alterations and damage hereditary material (DNA) and CAN cause cancer
can mutations be passed dow to future generations unless in germline cells
no
carcinogens
mutagenic agents that trigger cancer-causing mutations
what are the 2 groups of genes that are involved in regulating the cell cycle
proto-oncogenes and tumour suppressor genes
protooncogenes
generally maintain and promote growth and development of cells and promote progression through the cell cycle
what happens when protooncogenes are mutated
when mutated they turn into oncogenes that no longer regulate cell cycle progression. they deregulate the cell cycle-> overstimulation of growth signals
tumour suppressor genes
code for proteins that promote apoptosis, repressing progression. they inhibit cell growth promote apoptosis in damaged cells and decrease cell growth
mutated tumour suppressor genes
the cell cycle becomes deregulated resulting in uncontrollable division, antioncogenes
cancer
uncontrolled cell division because of mutations, forming abnormal cell growths
benign or malignant. a disease caused by the uncontrolled replication of cells with the ability to migrate to other parts of the body
benign tumours
a tumour that cannot spread throughout other tissues and organs. relatively slow-growing masses of cells that are enclosed in a capsule that prevents abnormal cells from separating
malignant tumours
cells of some benign tumours can mutate further and become malignant where they gain the ability to invade nearby tissues and/or enter the bloodstream or lymphatic system. thus spreading to other parts of the body
metastasis
spread of a primary tumour to another location, secondary tumour
how are secondary tumours defined
secondary tumours are defined according to the origin of the primary tumour
cancer cells
large, variable-shaped nuclei with small cytoplasmic volume- the tumours have formed new blood vessels and increased survival
may vary in size and shape and cells are disorganised in shape
lose the ability to specialise and elevate the expression of cell markers
lots of dividing cells and poorly defined tumour boundaries
syndactyly
apoptosis doesn’t occur between fingers
abnormal embryonic development
if embryonic development like mitosis and apoptosis don’t occur properly to form body systems and limbs then abnormal embryonic development occurs
stem cells
undifferentiated cells that can become other cells
what can stem cells do
self renew-> continually divide and replicate to repopulate an entire cell line
potency-> capacity to differentiate into other cell types
what are the ways potency can be classified?
totipotent, pluripotent, multipotent, unipotent
totipotent
can differentiate into any cell species and give rise to new organisms.
e.g. zygotes-> fertilised eggs.
toti-totally
pluripotent
differentiates into many types of cells like those found in an embryo
multipotent
differentiate into cells for certain tissue/organs and are specific like bone marrow stem cells that produce blood cells
unipotent
can’t differentiate any more but can self renew
endoderm line
endo-> enter, inner germ line layer
mesoderm line
middle germ line layer
ectoderm
outer germ line layer
what are some multipotent stem cells that come from the endoderm
lung or pancreatic cells
what are some multipotent stem cells that come from the mesodermic line
heart or muscle cells or red blood cells
what are some multipotent stem cells that come from the ectodermic line
skin or neurons
what is the process from ovulation to implantation to embryos
Day 0: oocyte 1 cell unfertilised
Day 1:zygote 1 cell fertilised
Day 2: first cleavage, mitosis 2 cells
Day 1-5: cell division
Day 5: morula
Day 6: blastocyst
After 3 weeks: gastrulation occurs, forming gastrula with 3 germ layers of multipotent cells
types of stem cell research as a treatment
cell based therapy for diseases linked with excessive cell death
producing human cells for medical trials
produce human cells to test how disease effets cells and system
how can adult stem cells be used
can be harvested from placenta, umbilical cord or bone marrow- pluripotent or multipotent
embryonic stem cells that are totipotent are more useful but have ethical issues
