chapter 6 Flashcards
what are the two parts of the cell cycle
interphase and mitotic phase
what are the three stages to interphase
G1 - proteins are made, cell gets bigger and organelles replicate
S - DNA is replicated (in nucleus)
G2 - cell gets bigger, energy stores increase and DNA is checked for errors
what is the mitotic phase and its two stages
its where the cell divides
mitosis - division of the nucleus
cytokinesis - cytoplasm divides and cells divide
what is the G0 stage
ite where cells leave the cell cycle and go into a resting state
what are the reasons for cells leaving the cell cycle
differentation - they carry out their own jobs and are no longer able to divide
damage - the DNA may be damaged so no longer can be used
what are checkpoints in the cell cycle
they moniter and verify that the cells have gone through the stages correctly without fault
where are the different checkpoint in the cell cycle
G1 - G1 checkpoint makes sure the cell has grown, got its nutrients and has no DNA damage
G2 - G2 checkpoint makes sure the cell has grown, has no DNA damage and has replicated its DNA
spindle - the spindle fibre checkpoint checks whether the chromasomes has attached to the spindle fibres
what happens if the checpoint picks up something wrong about the cell
it goes into the resting state G0
what phase does cell replication happen in
interphase
whatsa a chromatid
during replication each DNA molecule is converted into two identical DNA molecules called chromatids
what are the four stages to mitosis
PMAT
prophase
metaphase
anaphase
telephase
what happens in prophase
nuclear membrane starts to break down
chromatid condence making chromasomes
centrioles go to opposite poles
chromosomes are slowly moved to center of the cell
what happens in metaphase
where the chromosomes line up along the equator
its called the metaphase plate
what happens in anaphase
the pairs of chromatids divide
make V across the spindle fibres
what happens in telephase
chromatids have reached poles
nuclear envelope start to form around them
nucleus forms
cytokenisis in animals
pulls the membrane in
creates a cleavage furrow down the middle
two daughter cells made
cytokenisis in plants
no membrane so no furrow
vesicles from golgi appuratus line up down the middle where the metaphase plate was
cell wall starts to form
two daughter cells made
What does mitosis produce?
The nuclear division, producing two, genetically identical daughter cells = exact copy of the parents DNA and same number of chromosomes.
4 stages of meiosis 1
prophase 1
metaphase 1
anaphase 1
telophase 1
what happens in prophase one
chromosomes condense
nuclear envelope dissolves
nucleolus dissapears
spindle fibres form
homologous chromosomes pairs up
th chromatids could entangle in the transportation
what happens in metaphase 1
homologous chromosomes line up on the metabolic plate
orientation of the pairs are random
different assortment of chromosomes create genetic variation
what’s anaphase 1
homologous chromosomes are pulled to opposite poles
some DNA sister chromatids which entangle with each other break off and rejoin
this means an exchange in DNA
which could result in genetic variation
what’s telophase 1
same as mitosis telophase
nuclear membrane forms around the chromosomes
cell undergoes cytokenisis
what’s prophase 2
spindle fibres form
chromosomes condense
nuclear envelope breaks down
what’s metaphase 2
individual chromosomes line up on the metaphase plate
what’s anaphase 2
chromatids get pulled by spindle fibres attached to centromeres
what’s telephase 2
chromatids assemble at poles and turn in to chromatins
nuclear envelope forms
then cytokinesis leads to the separation in 4 separate haploid cells
what’s an erythrocyte (red blood cell)
biconcave disc to increase surface area
transports oxygen in the body
has haemoglobin
flexible to squeeze through capillaries
no nucleus so more room for haemoglobin
what’s neutrophil
a white blood cell
has a multi lobed nucleus to squeeze though small gaps to get to infections
has a granular cytoplasm containing lysosomes that contain enzymes to attack pathogens
what’s sperm cell
male gametes
flagella help it to propel towards the female gamete
digestive enzymes on the head help to break down the eggs layers
has lots of mitochondria for energy
what’s root hair cell
good SA:V ratio
uptakes minerals and water from the soil
what’s palisade cell
contains chloroplasts
rectangle to pack together
thin cell wall to increase rate of diffusion of carbon dioxide
large vacuole to maintain turgor pressure
what’s a guard cell
on surface of leaves
CO2 enters through this
no water they are flaccid and closed
water they are turgid
what’s squamous epithelium
flat and thin
one cell thick
rapid diffusion so is used in lining of the lungs which allows for rapid diffusion of O2 toblood
what’s ciliated epithelium
cilia on surface
lines trachea
what’s cartilage
connective tissue
elastin and collegan
cartilage is firm and flexible so is perfect to prevent rubbing at end of the bones
what’s muscle
it contacts so you can move
heart cant beat
what’s epidermis
single layer closely packed
on the surface of plants
covered by a waxy cuticle to reduce water loss
stomata are in the epidermis which alows for CO2, water and oxgygen in and out
Chromosomes
Structures of condensed and coiled DNA in the form of chromatin.
Chromatids
Two identical copies of DNA held together at the centromere
Chromatin
Uncondensed DNA in a complex with histones
Meiosis
A form of cell division where the nucleus divides twice, resulting in half the number of chromosomes and producing 4 haploid cells from one diploid cell.
Gametes
Haploid sex cells produced by meiosis in organisms that reproduce sexually
Zygote
The initial diploid cell formed when 2 gametes are joined by the means of sexual reproduction
Haploid
Half the number of normal chromosome number; one chromosome of each type
Homologous chromosomes
Matching pair of chromosomes, one from each parent
Alleles
Different versions of the same gene
Genetic variation
A variety of different combinations of alleles in a population.
Crossing over
Sections of DNA which become entangled, breaks and re-joins during prophase 1 of meiosis = genetic variation
Independent assortment
The arrangement of each homologous chromosome pair in metaphase 1 and 2 of meiosis is independent of each other and results in genetic variation
Stem cell
Undifferentiated cells with the potential to differentiate into any of the specialised cell types of the organism
Potency
The ability to differentiate into different cell types
Totipotent
These can differentiate into any type of cell
Pluripotent
These can form all tissue types but not whole organisms
Multipotent
Only form a range of cells within a certain type of tissue
Sources of animal stem cells
Embryonic stem cells, tissue stem cells
Embryonic stem cells
Present at the very early stages of embryo development and are totipotent
Tissue stem cells
Present throughout life, from birth to death. Found in specific areas e.g. bone marrow. Multipotent. Can be harvested from the umbilical cord of new babies
Sources of plant stem cells
In meristematic tissue
Meristematic tissue
Found wherever the plant is growing e.g. root tips. Also between xylem and phloem.
Potential usage of stem cells in treatment for:
Heart disease, type 1 diabetes, Parkinson’s disease, Alzheimer’s disease, muscular degeneration, birth defects, spinal injury
Current usage of stem cells in areas such as:
Burn treatment, drug trial, developmental biology
Ethics
Embryos - religious and moral judgement. murder.
