2.1.6 Cell division Flashcards
What is the name of the process that the cell is in during its majority of time?
interphase
What does interphase include?
G1, S and G2
What occurs in G1?
growth of cells;
growth of organelles;
increase in no. of organelles;
proteinsynthesis
What occurs in G2?
growth of cells;
growth of organelles;
increase in no. of organelles;
proteinsynthesis;
spindle fibres begin to form;
What occurs in the S phase?
DNA replication = must occur so that the daughter cells have the same/identical DNA and a full copy of DNA
What are the uses of mitosis?
growth of organism
repair of tissues
replacement of old cells
asexual reproduction
What occurs in G0 and where is it located?
after the mitosis stage
enters when:
- cell is fully differentiated
- DNA in the cell is damage = repair DNA
What occurs in G1 and where is it located?
occurs between G1 and S phase
enters when:
- check to see if all the chemicals needed are met if not = enters G0
What occurs in G2 and where is it located?
after the G2 stage
enters when:
- checks for mutation in DNA
- daughter cells may not recieved identical genetic info
- proteins may no function = enter G0
What occurs at the metaphase checkpoint?
checks to see if the spindle fibres have aligned correctly
What are the stages of mitosis?
prophase
metaphase
anaphase
telophase
What occurs in prophase?
nuclear envelope breaks down;
chromosomes condense;
spindle fibres attach to the centromere of the chromosomes;
How do the chromosomes condense?
DNA is wrapped around histone proteins = visible by microscope
What occurs in metaphase?
chromosomes line up at the equator of the cell;
spindle fibres attach to the centromeres of the chromosomes
What occurs during anaphase?
chromatids are pulled to opposite poles of the cell;
by the spindle fibres contracting;
centromere breaks;
What occurs during telophase?
nuclear envelope reforms;
chromosomes uncoil;
cell surface membrane undergoes cytokinesis;
spindle fibres break down;
What occurs during cytoskinesis?
the cell pinches into two, forming 2 genetically identical cells
How does cytokinesis occurs in plants?
cell plates form;
by the golgi apparatus and vesicles = assemble at the equator and deposit contents;
some vesicles make connecting channels = plasmodesmata through new cell wall
What experiment can we use to prepare microscope slide to observe mitosis?
root tip squash
PAG; Why do you head the plant sample in acid?
to break down the cell wall
PAG; Why do you stain the sample?
provides contrast;
makes chromosomes more visible
PAG; why is it important to ‘squash’ the sample?
to make it as thin as possible = light can pass through
What does meiosis produce?
non-genetically identical daughter cells;
gametes;
haploid;
What are homologous chromosomes?
chromosomes that have;
- same shape and size
- centromere in the same position
- same genes in the same position on chromosomes
- one maternal one paternal
What occurs during prophase I ?
chromosomes condense;
homologous chromosomes pair up to form bivalents;
chromatids in each bivalent break off and form chiasma = crossing over;
nuclear envelope breaks down;
spindle fibres form;
What occurs during metaphase 1 ?
spindle fibres attack to the centromeres of chromosomes;
bivalents move to the equator of the cell;
independent assortment occurs;
(orientation of each bivalent is random)
What occurs during anaphase I ?
spindle fibres contract;
separate bivalent to opposite poles;
each chromosomes still contains two chromotids;
What occurs during telophase I?
nuclear membrane reforms;
chromosomes uncoil and form two nuclei = each has half the number of chromosomes than the beginning
What is different in prophase 2 than prophase 1?
no crossing over
What is the same in metaphase 1 and 2?
independent assortment still occurs
What occurs in anaphase 2 that doesn’t occur in anaphase I?
centromere breaks
How many cells does meiosis produce?
4 genetically different daughter cells
Why is it important that gametes are haploid?
when they become fertilised = becomes a diploid zygote
How does genetic variation occur in meiosis?
prophase I = crossing over
metaphase I : independent assortment
metaphase II: independent assortment
How are erythrocytes specialised?
small - fit through capillaries
no nucleus/organelles - space for heamoglobin = carry large volume of oxygen
biconcave shape = increases SA:V = gas exchange more efficent/takes up oxygen quickly
How are neutrophils specialised?
lobed nucleus
granular cytoplasm = lots of lysosomes = contain digestive enzymes
flexible shape = enables movement through tissues
membrane bound receptors = recognise material that needs to be destroyed
How are squamous epithelial cells specialised?
used to line blood vessels
flattened smooth, thin surface = short diffusion distance = gas exchange is efficient
How are ciliated epithelial cells specialised?
column shaped cells
cilia wave in a synchronised rhythm = move more mucus that are secreted by goblet cells
How are sperm cells specialised?
lots of mitochondria = movement
acrosome = digestive enzymes = penetrate egg
shape = streamlines = aid movement
contains half no. of chromosomes = when fertilised = diploid zygotes
How are palisade cells specialised?
long think and packed
contain chloroplast = absorb photons of light for photosynthesis
starch grains = store products of photosynthesis
spongy mesophyll = air space = air circulation
How are root hair cells specialised?
absorb water and mineral ions through soil
long hair extensions = increase SA
thin walls = efficient exchange
cytoplasm = extra mitochondria for ATP for active transport
What is a tissue?
same type of cells working together for the same function
Give 4 examples of tissues and where they are found?
epithelial = line organs to separate
connective = support and structure
muscle = contract
nerve = conduct electrical signals
What are organs?
group of tissues working together for the same function
What is an organ system?
made up of 2 or more organs working together to perform a life function
How do cartilage and muscle tissue work together in the body?
cartilage = holds the trachea open under negative
muscle = contract to constrict airway
= controls ventilation in the lungs
What are stem cells?
undifferentiated cells
that can differentiate into any cell type
via mitosis
What are totipotent stem cells?
can differentiate into any body and extra embryonic cell e.g placenta/umbilical cord
what are pluripotent stem cells?
taken from the blastocyst
can form different body cells
cant form extra embryonic cells
What ate multipotent stem cells?
found in adults: bone marrow/ribs
bane marry = haematopoietic
can form more than one type/limited
How are erythrocytes produced from multipotent stem cells?
stem cell would need to remove nucleus
produce lots of haemoglobin
How are neutrophils produced from multipotent stem cells?
stem cell changes nucleus to lobed nucleus
produce lots of lysosomes
Where are stem cells found in plant?
vascular cambium = meristem
How are xylem cells formed?
walls are deposited with lignin = provides strength against negative pressure
cell dies
creates hollow tube
limits lateral movement of water
allows adhesion
also has pits = allows lateral movement of water
How are phloem vessels created?
sieve tube elements = loose nucleus and organelles
companion cells = metabolically active to provide ATP
plasmodesmata
What are the potential uses of stem cells?
How are stem cells used in medicine?
bone marrow = leukaemia
repair spinal cords in rats
treat mice with type 1 diabetes
Alzhiemers disease
How can stem cells be used in the future?
study what happens when differentiation goes wrong
see if they can re-enable differentation and growth in adults
