Cell division, Cell diversity and Cellular organisation Flashcards
3 phases of cell cycle
interphase, mitotic phase, G0 phase
interphase
time of growth and preparation for cellular division
DNA replicated and checked for errors
protein synthesis in cytoplasm
chloroplast and mitochondria grow in number
stages of interphase
g1- growth phase(organelles produced and replicate
S- DNA replication
g2- second growth phase continued growth in size and DNA checked for error
miotic phase
mitosis- nucleus divides
cytokinesis - cytoplasm divides
G0
cell leaves cycle temporarily or permamently
differentiation- cell specialised to carry out a function can no longer divide
DNA might be damaged so it enters arrrest apoptosis
how do chromosomes act in mitosis
DNA molecules converted into two identical DNA molecules called chromatid joined together by the centromere
important to be kept together to be precisely manoeuvred/ segregated
what is the importance of mitosis
ensures both daughter cells are genetically identical to the parent cells, they will have the exact copy of DNA in present cells and the same number of chromosomes
growth, repair, asexual reproduction
how is the cell cycle controlled
checkpoints are done to ensure the cell is process of each phase has been accurately completed
G1check point- end of g1 phase makes sure cell has met requirements
G2check point- at the end of the G2 phase(checks DNA has been replicated properly and cell begins mitosis
spindle checkpoint- makes sure all of the chromosomes are correctly attached to the spindles
what are the stages of mitosis
prophase, metaphase, anaphase and telophase
they are all interlinked and work between themselves
Prophase
chromatin condenses and becomes visible and nuclear membrane breaks down
microtubules form spindle shaped structures linking poles of the cell
centrioles migrate to the poles of cell to help the formation of the spindle fibres
the spindle fibres attach to parts of the chromosomes and move to metaphase plate
at the end nuclear envelope has disappeared
metaphase
chromosomes moved by the spindle fibres to the metaphase plate and lined upheld in position
Anaphase
The spindle fibres attach to the centromeres of the chromosome on both sides and splits it in two, fibres contract and pull the chromatids to each side of the cell
telophase
Once the chromatids reach the poles they are called chromosomes, new sets of chromosomes assemble at the poles and the nuclear envelope forms around them, chromosomes uncoil and nucleolus forms
cytokinesis
actual splitting of the membrane into two different cells
animal cytokinesis
cleavage furrow forms around middle of the cell membrane pulled inwards until it can fuse with itself and pinch of into two
plant cell cytokinesis
cell wall stops cleavage furrow, so vesicles from the Golgi apparatus assemble at the metaphase plant all using together until the cell is split into two and new cell walls form around the membranes
what type of chromosomes are made in mitosis
diploid
what type of chromosomes are made in meosis
haploid
what are homolgus chromosomes
chromosomes from each parent that have the same matching genes(pair) for each characteristic)
same genes in the same posititns
Allele?
different versions of the same gene eg the gene for eye colour varies blue/ brown eyes
what are the stages of meiosis
meiosis 1- reduction division when the pairs of chromosomes are separated in two cells
meiosis 2- second division pair of chromosomes are separated forming 2 more cells 4 haploid daughter cells in total
Meiosis 1(p1)
-chromosomes condense nuclear envelope/ nucleolus disappears
-spindle fibres begin to form
-homologous chromosomes pair up (bivalents)
-chromosomes are large molecules and as they move around in cytoplasm they get entangled and DNA crosses over
Meiosis1(m1)
homologous pairs of chromosomes assemble on the metaphase plate
assembly of the homologous chromosomes on the metaphase plate is random maternal/ paternal chromosomes can end up facing either pole(independent assortment)
Meiosis1(anaphase 1)
homologous chromosomes pulled apart but the chromatid stay together
crossing over
When entangled chromatids are pulled apart they break off and exchange DNA points at which they break/join (chiasmata)
when re-joined they form recombinant chromosomes
genes shared (different alleles for genetic variation
meiosis1(T1)
same as mitosis
chromosomes assemble they uncoil membrane reforms and cytokinesis divides the two cells
haploid cells
meiosis2(p2)
chromosomes consist of 2 chromatid condense and become visible
nuclear envelope breaks down
spindle fibres form
meiosis2(m2)
individual chromosomes line up at metaphase plate
chromatids aren’t identical so there is independent assortment and more genetic variation
meiosis2(a2)
chromatids of individual chromosomes pulled to opposite poles after centromere division
meiosis2(t2)
assemble at the poles uncoil into chromatin nuclear envelope and nucleolus appear
cytokinesis causes the cells to be 4 daughter haploid cells which are genetically varied
levels of organism?
specialised cells- tissues-organs-organ systems- whole organism
Specialised cells
differentiated, meaning they are specialised for their function
erythrocytes specialisations
flattened biconcave for large SA:VOL ratio for o2 transport
have no nucleus more space for haemoglobin
flexible to squeeze through capillaries
neutrophils(wbc) specialisations
multi loved nucleus to squeeze though small gaps for infections
granular cytoplasm with many lysosomes that contain enzymes to attack pathogens
Sperm cells specialisations
deliver genetic information
tail/flagellum to move
plentiful mitochondria to supply the energy needed to swim
acrosome that contain digestive enzymes to penetrate the egg
Palisade cells
Large amounts of chloroplasts for light absorption. Thin cell walls which increases rate of diffusion for Co2 ,choloroplast can move in the cytoplasm
root hair cells
Large surface rea for maximum water uptake from the soil
Guard cells
form opening of stomata, change shape to prevent water loss. cell wall thicker on one side shape symmetrically as the volume changes
categories of tissues
nervous tissue; adapted to support transmission of electrical impulses
epithelial tissue; adapted to cover body surfaces (internal/external)
muscle tissue; adapted to contract
connective tissue; to hold other tissues together or a transport medium
squamous epithelium
flat cells and thin(one cell thick)
for fast diffusion of gaseous material
in lung lining for rapid diffusion of o2 into the blood
ciliated epithelium
line with cilia that beat to move mucus/ trapped particles out of trachea
they have goblet cells that secrete mucus to trap any pathogens
cartilage
connective tissue contains fibres of elastin and collagen.
firm tissue that prevents ends of bones from rubbing together
muscle
can shorten and contract which moves the body
skeletal muscles fibres( attached to bone)
contains myofibrils and contractile proteins
epidermis
closely pack cells on plant surface which is covered by a waxy cuticle to reduce water loss
stomata are present in the epidermis
xylem tissue
transport of water/ minerals throughout plants
composed of vessel elements which are elongated dead cells
strengthened by lining water proof and provides strength
phloem tissue
transports of assimilates(sucrose mainly)
from leaves to where it is needed, column of sieve tube elements separated by sieve plates
organ systems
digestive system, cardiovascular system, gaseous exchange system
what is a stem cell
an undifferentiated cell that can differentiate into any cell, can keep dividing and be a source for cells necessary for growth, development and repair. Once specialised they can no longer divide
too slow division leads to aging to fast division leads to cancer
what is stem cell potency
ability for a cell to differentiate (potency)
totipotent-
can differentiate into any type of cell, fertilised egg, zygote are totipotent cells meaning they can produce a whole organism
pluripotent
can form all tissue but not whole organisms, mainly in early embryos origin of different tissues in a cell
multipotent
wide range of cells within a certain tissue(haemopoietic can give rise to different types of blood types in the bone marrow )
differentiation
when cells change shape for certain functions or a specific roles
all RBC come from stem cells in the bone marrow
replacement of red and white blood cells
they lack organelles and have a short life span(120) need to be replaced constantly
stem cell colonies produce 3 billion erythrocytes per kg of body mass every day
neutrophils live about 6 hours so stem cell colonies in bone marrow produce about 1.6 billion per kg per hour of WBC which increases during infection
what are the sources of stem cells
embryonic stem cells- early stage of development they are totipotent, after 7 days they become blastocyst and the cells are now pluripotent
adult stem cells- throughout a persons life time, found in bone marrow they are multipotent but can be triggered to become pluripotent
whys are embryonic cells preferred
plenty umbilical cords to use and there is no need for an invade process to remove the stem cells
what is the source of stems cells in plants
meristematic tissue which is found where growth occurs in plants(root/shoot)
also found between the phloem and xylem (vascular cambium) which differentiate into xylem or phloem cells
Use of stem cells
heart disease
muscle tissue damaged from heat attack
embryo creation
embryos created intentionally to take the cells away from them and kill the cells controversy as to if the cell has rights or not